What is the longest-lasting protein in a human body?











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Protein life times are, on average, not particularly long, on a human life timescale.
I was wondering, how old is the oldest protein in a human body? Just to clarify, I mean in terms of seconds/minutes/days passed from the moment that given protein was translated. I am not sure is the same thing as asking which human protein has the longest half-life, as I think there might be "tricks" the cell uses to elongate a given protein's half-life under specific conditions.



I am pretty sure there are several ways in which a cell can preserve its proteins from degradation/denaturation if it wanted to but to what extent? I accept that a given protein post-translationally modified still is the same protein, even if cut, added to a complex, etc. etc.



And also, as correlated questions: does the answer depend on the age of the given human (starting from birth and accepting as valid proteins translated during pregnancy or even donated by the mother)? What is the oldest protein in a baby's body and what is in a elderly's body? How does the oldest protein lifetime does in comparison with the oldest nucleic acid/cell/molecule/whatever in our body?










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  • 1




    Maternally contributed antibodies? They could be older than you if there are any that persist life-long.
    – Armatus
    2 days ago






  • 11




    Half-Baked suggestion: consider changing the title to ask for the "longest-lasting" protein in the human body. When I first read the title, I wasn't sure if it was asking for the longest-lasting protein, or the protein that has been around the longest in evolutionary terms.
    – Randall Stewart
    2 days ago










  • would there be a protein that is taken from the environment and cannot be produced inside the body? Like vitamins?
    – Ooker
    2 days ago






  • 1




    @Armatus Antibodies do not and cannot persist lifelong. They're actually destroyed at a rather rapid rate.
    – forest
    2 days ago















up vote
48
down vote

favorite
4












Protein life times are, on average, not particularly long, on a human life timescale.
I was wondering, how old is the oldest protein in a human body? Just to clarify, I mean in terms of seconds/minutes/days passed from the moment that given protein was translated. I am not sure is the same thing as asking which human protein has the longest half-life, as I think there might be "tricks" the cell uses to elongate a given protein's half-life under specific conditions.



I am pretty sure there are several ways in which a cell can preserve its proteins from degradation/denaturation if it wanted to but to what extent? I accept that a given protein post-translationally modified still is the same protein, even if cut, added to a complex, etc. etc.



And also, as correlated questions: does the answer depend on the age of the given human (starting from birth and accepting as valid proteins translated during pregnancy or even donated by the mother)? What is the oldest protein in a baby's body and what is in a elderly's body? How does the oldest protein lifetime does in comparison with the oldest nucleic acid/cell/molecule/whatever in our body?










share|improve this question









New contributor




JalfredP is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
















  • 1




    Maternally contributed antibodies? They could be older than you if there are any that persist life-long.
    – Armatus
    2 days ago






  • 11




    Half-Baked suggestion: consider changing the title to ask for the "longest-lasting" protein in the human body. When I first read the title, I wasn't sure if it was asking for the longest-lasting protein, or the protein that has been around the longest in evolutionary terms.
    – Randall Stewart
    2 days ago










  • would there be a protein that is taken from the environment and cannot be produced inside the body? Like vitamins?
    – Ooker
    2 days ago






  • 1




    @Armatus Antibodies do not and cannot persist lifelong. They're actually destroyed at a rather rapid rate.
    – forest
    2 days ago













up vote
48
down vote

favorite
4









up vote
48
down vote

favorite
4






4





Protein life times are, on average, not particularly long, on a human life timescale.
I was wondering, how old is the oldest protein in a human body? Just to clarify, I mean in terms of seconds/minutes/days passed from the moment that given protein was translated. I am not sure is the same thing as asking which human protein has the longest half-life, as I think there might be "tricks" the cell uses to elongate a given protein's half-life under specific conditions.



I am pretty sure there are several ways in which a cell can preserve its proteins from degradation/denaturation if it wanted to but to what extent? I accept that a given protein post-translationally modified still is the same protein, even if cut, added to a complex, etc. etc.



And also, as correlated questions: does the answer depend on the age of the given human (starting from birth and accepting as valid proteins translated during pregnancy or even donated by the mother)? What is the oldest protein in a baby's body and what is in a elderly's body? How does the oldest protein lifetime does in comparison with the oldest nucleic acid/cell/molecule/whatever in our body?










share|improve this question









New contributor




JalfredP is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.











Protein life times are, on average, not particularly long, on a human life timescale.
I was wondering, how old is the oldest protein in a human body? Just to clarify, I mean in terms of seconds/minutes/days passed from the moment that given protein was translated. I am not sure is the same thing as asking which human protein has the longest half-life, as I think there might be "tricks" the cell uses to elongate a given protein's half-life under specific conditions.



I am pretty sure there are several ways in which a cell can preserve its proteins from degradation/denaturation if it wanted to but to what extent? I accept that a given protein post-translationally modified still is the same protein, even if cut, added to a complex, etc. etc.



And also, as correlated questions: does the answer depend on the age of the given human (starting from birth and accepting as valid proteins translated during pregnancy or even donated by the mother)? What is the oldest protein in a baby's body and what is in a elderly's body? How does the oldest protein lifetime does in comparison with the oldest nucleic acid/cell/molecule/whatever in our body?







molecular-biology proteins senescence protein-expression






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edited yesterday









Ben Crowell

56559




56559






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asked Nov 28 at 23:05









JalfredP

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  • 1




    Maternally contributed antibodies? They could be older than you if there are any that persist life-long.
    – Armatus
    2 days ago






  • 11




    Half-Baked suggestion: consider changing the title to ask for the "longest-lasting" protein in the human body. When I first read the title, I wasn't sure if it was asking for the longest-lasting protein, or the protein that has been around the longest in evolutionary terms.
    – Randall Stewart
    2 days ago










  • would there be a protein that is taken from the environment and cannot be produced inside the body? Like vitamins?
    – Ooker
    2 days ago






  • 1




    @Armatus Antibodies do not and cannot persist lifelong. They're actually destroyed at a rather rapid rate.
    – forest
    2 days ago














  • 1




    Maternally contributed antibodies? They could be older than you if there are any that persist life-long.
    – Armatus
    2 days ago






  • 11




    Half-Baked suggestion: consider changing the title to ask for the "longest-lasting" protein in the human body. When I first read the title, I wasn't sure if it was asking for the longest-lasting protein, or the protein that has been around the longest in evolutionary terms.
    – Randall Stewart
    2 days ago










  • would there be a protein that is taken from the environment and cannot be produced inside the body? Like vitamins?
    – Ooker
    2 days ago






  • 1




    @Armatus Antibodies do not and cannot persist lifelong. They're actually destroyed at a rather rapid rate.
    – forest
    2 days ago








1




1




Maternally contributed antibodies? They could be older than you if there are any that persist life-long.
– Armatus
2 days ago




Maternally contributed antibodies? They could be older than you if there are any that persist life-long.
– Armatus
2 days ago




11




11




Half-Baked suggestion: consider changing the title to ask for the "longest-lasting" protein in the human body. When I first read the title, I wasn't sure if it was asking for the longest-lasting protein, or the protein that has been around the longest in evolutionary terms.
– Randall Stewart
2 days ago




Half-Baked suggestion: consider changing the title to ask for the "longest-lasting" protein in the human body. When I first read the title, I wasn't sure if it was asking for the longest-lasting protein, or the protein that has been around the longest in evolutionary terms.
– Randall Stewart
2 days ago












would there be a protein that is taken from the environment and cannot be produced inside the body? Like vitamins?
– Ooker
2 days ago




would there be a protein that is taken from the environment and cannot be produced inside the body? Like vitamins?
– Ooker
2 days ago




1




1




@Armatus Antibodies do not and cannot persist lifelong. They're actually destroyed at a rather rapid rate.
– forest
2 days ago




@Armatus Antibodies do not and cannot persist lifelong. They're actually destroyed at a rather rapid rate.
– forest
2 days ago










4 Answers
4






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up vote
64
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Crystallin proteins are found in the eye lens (where their main job is probably to define the refractive index of the medium); they are commonly considered to be non-regenerated. So, your crystallins are as old as you are!



Because of this absence of regeneration, the accumulate damage over time, including proteolysis, cross-linkings etc., which is one of the main reasons why visual acuity decays after a certain age: that is where cataracts come from. The cloudy lens is the result of years of degradation events in a limited pool of non-renewed proteins.






share|improve this answer













Some of the information contained in this post requires additional references. Please edit to add citations to reliable sources that support the assertions made here. Unsourced material may be disputed or deleted.










  • 12




    To back this up: Crystallin proteins were used to determine the age of Greenland sharks. Source
    – daign
    Nov 29 at 17:01








  • 6




    Great answer, but can you give references? :)
    – SEwontLetMeDeleteProfile
    Nov 29 at 17:54






  • 3




    Nice answer, thanks. I would also like some references. I am waiting for some new answers before confirming the best one, but you are a good candidate :)
    – JalfredP
    2 days ago










  • I agree it is almost certainly in the eye, but why Crystallin specifically?
    – John
    2 days ago






  • 5




    Supported by Identification of long-lived proteins reveals exceptional stability of essential cellular structures and Protein homeostasis: live long, won’t prosper; in particular see Table 1 in the latter
    – iayork
    2 days ago


















up vote
21
down vote













I like Mowgli's answer, because it is a non-obvious example. However I would also point out that there are many, many protein-based structural components in the body that we know do not regenerate due to associated pathologies; so presumably these structural proteins are as old as from when they first arose in developemnt. Take the stereocilia on hair cells in the cochlea, for instance. The stereocilia structure is actin-filament based, so is a structural protein. Hearing loss occurs due to damage to these structures, which is not repaired. In fact, birds suffer only temporary hearing loss not because they regenerate these structures, but because they grow replacement hair cells.



Once you start thinking about this then, it is pretty clear that many structural proteins will be conserved throughout life (if the cell they are attached to or within remains a part of the body). And many cells of the body remain in the body throughout life, so any proteins that join the cells together, say connexin proteins that form tight junctions between cells, would also presumably be conserved. I say this because I think the energetic cost of degrading a protein that spans two membranes would be too great for it to occur. I have not hear of tight junctions being eliminated, but I may be wrong.



Mowgli's answer is nice because it involves globular rather than fibrous proteins- though Wikipedia still classifies them as structural proteins. I was interested and read this article about them. Interesting stuff! Thank you Mowgli!



I would be interested to know if there are any conserved biochemically active proteins. I would think that extracellular proteins would probably be turned over, and the best chance of finding such a conserved protein would be within a cell that remains for life post differentiation. Perhaps a proteosome complex itself (these are the protein complexes that are involved in protein degradation)? I don;t think ribosomes are degraded either, but I don't find this a very satisfactory example!






share|improve this answer











Some of the information contained in this post requires additional references. Please edit to add citations to reliable sources that support the assertions made here. Unsourced material may be disputed or deleted.














  • Thank you for expanding Mowgli's answer! I personally work with actin in vitro and I never considered the fact that there could be years-old actin in our body (we usually frow away our stocks after a week :D )
    – JalfredP
    2 days ago










  • I would be very surprised if ribosomes were not degraded. And proteosomes do get degraded.
    – forest
    2 days ago




















up vote
8
down vote













A very interesting example are the cohesin molecules holding sister chromatids together in the oocytes (so only applicable to females, sorry!). Cohesion is established in utero, and these molecules are not recycled throughout life (AFAIK only shown directly for mice, not humans - https://www.ncbi.nlm.nih.gov/pubmed/20971813, https://www.ncbi.nlm.nih.gov/pubmed/26898469, but presumably same is true for us). This is considered to be a major contributor to the maternal age effect (https://en.wikipedia.org/wiki/Age_and_female_fertility) through low level loss of cohesion throughout life (since levels of cohesin can't be restored) until chromosomes start losing association between sisters which causes high chances of their missegregation (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5536066/)






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    up vote
    1
    down vote













    In terms of the common/abundant proteins, the answer would have to be elastin. The turnover is extremely slow, with a half-life of 74 years (https://www.elastagen.com/media/The_Science_of_Elastin.pdf) or "decades" according to other sources. In any case it is very slow - slow enough that most of it lasts a lifetime. It is a major constituent of the extracellular matrix but the rate of synthesis (and breakdown) is much slower than collagen (the other major structural protein). Reduced levels of elastin are one of the primary contributions to the aged look of older humans






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      4 Answers
      4






      active

      oldest

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      4 Answers
      4






      active

      oldest

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      active

      oldest

      votes






      active

      oldest

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      up vote
      64
      down vote













      Crystallin proteins are found in the eye lens (where their main job is probably to define the refractive index of the medium); they are commonly considered to be non-regenerated. So, your crystallins are as old as you are!



      Because of this absence of regeneration, the accumulate damage over time, including proteolysis, cross-linkings etc., which is one of the main reasons why visual acuity decays after a certain age: that is where cataracts come from. The cloudy lens is the result of years of degradation events in a limited pool of non-renewed proteins.






      share|improve this answer













      Some of the information contained in this post requires additional references. Please edit to add citations to reliable sources that support the assertions made here. Unsourced material may be disputed or deleted.










      • 12




        To back this up: Crystallin proteins were used to determine the age of Greenland sharks. Source
        – daign
        Nov 29 at 17:01








      • 6




        Great answer, but can you give references? :)
        – SEwontLetMeDeleteProfile
        Nov 29 at 17:54






      • 3




        Nice answer, thanks. I would also like some references. I am waiting for some new answers before confirming the best one, but you are a good candidate :)
        – JalfredP
        2 days ago










      • I agree it is almost certainly in the eye, but why Crystallin specifically?
        – John
        2 days ago






      • 5




        Supported by Identification of long-lived proteins reveals exceptional stability of essential cellular structures and Protein homeostasis: live long, won’t prosper; in particular see Table 1 in the latter
        – iayork
        2 days ago















      up vote
      64
      down vote













      Crystallin proteins are found in the eye lens (where their main job is probably to define the refractive index of the medium); they are commonly considered to be non-regenerated. So, your crystallins are as old as you are!



      Because of this absence of regeneration, the accumulate damage over time, including proteolysis, cross-linkings etc., which is one of the main reasons why visual acuity decays after a certain age: that is where cataracts come from. The cloudy lens is the result of years of degradation events in a limited pool of non-renewed proteins.






      share|improve this answer













      Some of the information contained in this post requires additional references. Please edit to add citations to reliable sources that support the assertions made here. Unsourced material may be disputed or deleted.










      • 12




        To back this up: Crystallin proteins were used to determine the age of Greenland sharks. Source
        – daign
        Nov 29 at 17:01








      • 6




        Great answer, but can you give references? :)
        – SEwontLetMeDeleteProfile
        Nov 29 at 17:54






      • 3




        Nice answer, thanks. I would also like some references. I am waiting for some new answers before confirming the best one, but you are a good candidate :)
        – JalfredP
        2 days ago










      • I agree it is almost certainly in the eye, but why Crystallin specifically?
        – John
        2 days ago






      • 5




        Supported by Identification of long-lived proteins reveals exceptional stability of essential cellular structures and Protein homeostasis: live long, won’t prosper; in particular see Table 1 in the latter
        – iayork
        2 days ago













      up vote
      64
      down vote










      up vote
      64
      down vote









      Crystallin proteins are found in the eye lens (where their main job is probably to define the refractive index of the medium); they are commonly considered to be non-regenerated. So, your crystallins are as old as you are!



      Because of this absence of regeneration, the accumulate damage over time, including proteolysis, cross-linkings etc., which is one of the main reasons why visual acuity decays after a certain age: that is where cataracts come from. The cloudy lens is the result of years of degradation events in a limited pool of non-renewed proteins.






      share|improve this answer














      Crystallin proteins are found in the eye lens (where their main job is probably to define the refractive index of the medium); they are commonly considered to be non-regenerated. So, your crystallins are as old as you are!



      Because of this absence of regeneration, the accumulate damage over time, including proteolysis, cross-linkings etc., which is one of the main reasons why visual acuity decays after a certain age: that is where cataracts come from. The cloudy lens is the result of years of degradation events in a limited pool of non-renewed proteins.







      share|improve this answer














      share|improve this answer



      share|improve this answer








      edited Nov 29 at 4:24

























      answered Nov 28 at 23:35









      Mowgli

      843111




      843111



      Some of the information contained in this post requires additional references. Please edit to add citations to reliable sources that support the assertions made here. Unsourced material may be disputed or deleted.




      Some of the information contained in this post requires additional references. Please edit to add citations to reliable sources that support the assertions made here. Unsourced material may be disputed or deleted.









      • 12




        To back this up: Crystallin proteins were used to determine the age of Greenland sharks. Source
        – daign
        Nov 29 at 17:01








      • 6




        Great answer, but can you give references? :)
        – SEwontLetMeDeleteProfile
        Nov 29 at 17:54






      • 3




        Nice answer, thanks. I would also like some references. I am waiting for some new answers before confirming the best one, but you are a good candidate :)
        – JalfredP
        2 days ago










      • I agree it is almost certainly in the eye, but why Crystallin specifically?
        – John
        2 days ago






      • 5




        Supported by Identification of long-lived proteins reveals exceptional stability of essential cellular structures and Protein homeostasis: live long, won’t prosper; in particular see Table 1 in the latter
        – iayork
        2 days ago














      • 12




        To back this up: Crystallin proteins were used to determine the age of Greenland sharks. Source
        – daign
        Nov 29 at 17:01








      • 6




        Great answer, but can you give references? :)
        – SEwontLetMeDeleteProfile
        Nov 29 at 17:54






      • 3




        Nice answer, thanks. I would also like some references. I am waiting for some new answers before confirming the best one, but you are a good candidate :)
        – JalfredP
        2 days ago










      • I agree it is almost certainly in the eye, but why Crystallin specifically?
        – John
        2 days ago






      • 5




        Supported by Identification of long-lived proteins reveals exceptional stability of essential cellular structures and Protein homeostasis: live long, won’t prosper; in particular see Table 1 in the latter
        – iayork
        2 days ago








      12




      12




      To back this up: Crystallin proteins were used to determine the age of Greenland sharks. Source
      – daign
      Nov 29 at 17:01






      To back this up: Crystallin proteins were used to determine the age of Greenland sharks. Source
      – daign
      Nov 29 at 17:01






      6




      6




      Great answer, but can you give references? :)
      – SEwontLetMeDeleteProfile
      Nov 29 at 17:54




      Great answer, but can you give references? :)
      – SEwontLetMeDeleteProfile
      Nov 29 at 17:54




      3




      3




      Nice answer, thanks. I would also like some references. I am waiting for some new answers before confirming the best one, but you are a good candidate :)
      – JalfredP
      2 days ago




      Nice answer, thanks. I would also like some references. I am waiting for some new answers before confirming the best one, but you are a good candidate :)
      – JalfredP
      2 days ago












      I agree it is almost certainly in the eye, but why Crystallin specifically?
      – John
      2 days ago




      I agree it is almost certainly in the eye, but why Crystallin specifically?
      – John
      2 days ago




      5




      5




      Supported by Identification of long-lived proteins reveals exceptional stability of essential cellular structures and Protein homeostasis: live long, won’t prosper; in particular see Table 1 in the latter
      – iayork
      2 days ago




      Supported by Identification of long-lived proteins reveals exceptional stability of essential cellular structures and Protein homeostasis: live long, won’t prosper; in particular see Table 1 in the latter
      – iayork
      2 days ago










      up vote
      21
      down vote













      I like Mowgli's answer, because it is a non-obvious example. However I would also point out that there are many, many protein-based structural components in the body that we know do not regenerate due to associated pathologies; so presumably these structural proteins are as old as from when they first arose in developemnt. Take the stereocilia on hair cells in the cochlea, for instance. The stereocilia structure is actin-filament based, so is a structural protein. Hearing loss occurs due to damage to these structures, which is not repaired. In fact, birds suffer only temporary hearing loss not because they regenerate these structures, but because they grow replacement hair cells.



      Once you start thinking about this then, it is pretty clear that many structural proteins will be conserved throughout life (if the cell they are attached to or within remains a part of the body). And many cells of the body remain in the body throughout life, so any proteins that join the cells together, say connexin proteins that form tight junctions between cells, would also presumably be conserved. I say this because I think the energetic cost of degrading a protein that spans two membranes would be too great for it to occur. I have not hear of tight junctions being eliminated, but I may be wrong.



      Mowgli's answer is nice because it involves globular rather than fibrous proteins- though Wikipedia still classifies them as structural proteins. I was interested and read this article about them. Interesting stuff! Thank you Mowgli!



      I would be interested to know if there are any conserved biochemically active proteins. I would think that extracellular proteins would probably be turned over, and the best chance of finding such a conserved protein would be within a cell that remains for life post differentiation. Perhaps a proteosome complex itself (these are the protein complexes that are involved in protein degradation)? I don;t think ribosomes are degraded either, but I don't find this a very satisfactory example!






      share|improve this answer











      Some of the information contained in this post requires additional references. Please edit to add citations to reliable sources that support the assertions made here. Unsourced material may be disputed or deleted.














      • Thank you for expanding Mowgli's answer! I personally work with actin in vitro and I never considered the fact that there could be years-old actin in our body (we usually frow away our stocks after a week :D )
        – JalfredP
        2 days ago










      • I would be very surprised if ribosomes were not degraded. And proteosomes do get degraded.
        – forest
        2 days ago

















      up vote
      21
      down vote













      I like Mowgli's answer, because it is a non-obvious example. However I would also point out that there are many, many protein-based structural components in the body that we know do not regenerate due to associated pathologies; so presumably these structural proteins are as old as from when they first arose in developemnt. Take the stereocilia on hair cells in the cochlea, for instance. The stereocilia structure is actin-filament based, so is a structural protein. Hearing loss occurs due to damage to these structures, which is not repaired. In fact, birds suffer only temporary hearing loss not because they regenerate these structures, but because they grow replacement hair cells.



      Once you start thinking about this then, it is pretty clear that many structural proteins will be conserved throughout life (if the cell they are attached to or within remains a part of the body). And many cells of the body remain in the body throughout life, so any proteins that join the cells together, say connexin proteins that form tight junctions between cells, would also presumably be conserved. I say this because I think the energetic cost of degrading a protein that spans two membranes would be too great for it to occur. I have not hear of tight junctions being eliminated, but I may be wrong.



      Mowgli's answer is nice because it involves globular rather than fibrous proteins- though Wikipedia still classifies them as structural proteins. I was interested and read this article about them. Interesting stuff! Thank you Mowgli!



      I would be interested to know if there are any conserved biochemically active proteins. I would think that extracellular proteins would probably be turned over, and the best chance of finding such a conserved protein would be within a cell that remains for life post differentiation. Perhaps a proteosome complex itself (these are the protein complexes that are involved in protein degradation)? I don;t think ribosomes are degraded either, but I don't find this a very satisfactory example!






      share|improve this answer











      Some of the information contained in this post requires additional references. Please edit to add citations to reliable sources that support the assertions made here. Unsourced material may be disputed or deleted.














      • Thank you for expanding Mowgli's answer! I personally work with actin in vitro and I never considered the fact that there could be years-old actin in our body (we usually frow away our stocks after a week :D )
        – JalfredP
        2 days ago










      • I would be very surprised if ribosomes were not degraded. And proteosomes do get degraded.
        – forest
        2 days ago















      up vote
      21
      down vote










      up vote
      21
      down vote









      I like Mowgli's answer, because it is a non-obvious example. However I would also point out that there are many, many protein-based structural components in the body that we know do not regenerate due to associated pathologies; so presumably these structural proteins are as old as from when they first arose in developemnt. Take the stereocilia on hair cells in the cochlea, for instance. The stereocilia structure is actin-filament based, so is a structural protein. Hearing loss occurs due to damage to these structures, which is not repaired. In fact, birds suffer only temporary hearing loss not because they regenerate these structures, but because they grow replacement hair cells.



      Once you start thinking about this then, it is pretty clear that many structural proteins will be conserved throughout life (if the cell they are attached to or within remains a part of the body). And many cells of the body remain in the body throughout life, so any proteins that join the cells together, say connexin proteins that form tight junctions between cells, would also presumably be conserved. I say this because I think the energetic cost of degrading a protein that spans two membranes would be too great for it to occur. I have not hear of tight junctions being eliminated, but I may be wrong.



      Mowgli's answer is nice because it involves globular rather than fibrous proteins- though Wikipedia still classifies them as structural proteins. I was interested and read this article about them. Interesting stuff! Thank you Mowgli!



      I would be interested to know if there are any conserved biochemically active proteins. I would think that extracellular proteins would probably be turned over, and the best chance of finding such a conserved protein would be within a cell that remains for life post differentiation. Perhaps a proteosome complex itself (these are the protein complexes that are involved in protein degradation)? I don;t think ribosomes are degraded either, but I don't find this a very satisfactory example!






      share|improve this answer












      I like Mowgli's answer, because it is a non-obvious example. However I would also point out that there are many, many protein-based structural components in the body that we know do not regenerate due to associated pathologies; so presumably these structural proteins are as old as from when they first arose in developemnt. Take the stereocilia on hair cells in the cochlea, for instance. The stereocilia structure is actin-filament based, so is a structural protein. Hearing loss occurs due to damage to these structures, which is not repaired. In fact, birds suffer only temporary hearing loss not because they regenerate these structures, but because they grow replacement hair cells.



      Once you start thinking about this then, it is pretty clear that many structural proteins will be conserved throughout life (if the cell they are attached to or within remains a part of the body). And many cells of the body remain in the body throughout life, so any proteins that join the cells together, say connexin proteins that form tight junctions between cells, would also presumably be conserved. I say this because I think the energetic cost of degrading a protein that spans two membranes would be too great for it to occur. I have not hear of tight junctions being eliminated, but I may be wrong.



      Mowgli's answer is nice because it involves globular rather than fibrous proteins- though Wikipedia still classifies them as structural proteins. I was interested and read this article about them. Interesting stuff! Thank you Mowgli!



      I would be interested to know if there are any conserved biochemically active proteins. I would think that extracellular proteins would probably be turned over, and the best chance of finding such a conserved protein would be within a cell that remains for life post differentiation. Perhaps a proteosome complex itself (these are the protein complexes that are involved in protein degradation)? I don;t think ribosomes are degraded either, but I don't find this a very satisfactory example!







      share|improve this answer












      share|improve this answer



      share|improve this answer










      answered Nov 29 at 13:07









      21joanna12

      1,5131834




      1,5131834



      Some of the information contained in this post requires additional references. Please edit to add citations to reliable sources that support the assertions made here. Unsourced material may be disputed or deleted.




      Some of the information contained in this post requires additional references. Please edit to add citations to reliable sources that support the assertions made here. Unsourced material may be disputed or deleted.













      • Thank you for expanding Mowgli's answer! I personally work with actin in vitro and I never considered the fact that there could be years-old actin in our body (we usually frow away our stocks after a week :D )
        – JalfredP
        2 days ago










      • I would be very surprised if ribosomes were not degraded. And proteosomes do get degraded.
        – forest
        2 days ago




















      • Thank you for expanding Mowgli's answer! I personally work with actin in vitro and I never considered the fact that there could be years-old actin in our body (we usually frow away our stocks after a week :D )
        – JalfredP
        2 days ago










      • I would be very surprised if ribosomes were not degraded. And proteosomes do get degraded.
        – forest
        2 days ago


















      Thank you for expanding Mowgli's answer! I personally work with actin in vitro and I never considered the fact that there could be years-old actin in our body (we usually frow away our stocks after a week :D )
      – JalfredP
      2 days ago




      Thank you for expanding Mowgli's answer! I personally work with actin in vitro and I never considered the fact that there could be years-old actin in our body (we usually frow away our stocks after a week :D )
      – JalfredP
      2 days ago












      I would be very surprised if ribosomes were not degraded. And proteosomes do get degraded.
      – forest
      2 days ago






      I would be very surprised if ribosomes were not degraded. And proteosomes do get degraded.
      – forest
      2 days ago












      up vote
      8
      down vote













      A very interesting example are the cohesin molecules holding sister chromatids together in the oocytes (so only applicable to females, sorry!). Cohesion is established in utero, and these molecules are not recycled throughout life (AFAIK only shown directly for mice, not humans - https://www.ncbi.nlm.nih.gov/pubmed/20971813, https://www.ncbi.nlm.nih.gov/pubmed/26898469, but presumably same is true for us). This is considered to be a major contributor to the maternal age effect (https://en.wikipedia.org/wiki/Age_and_female_fertility) through low level loss of cohesion throughout life (since levels of cohesin can't be restored) until chromosomes start losing association between sisters which causes high chances of their missegregation (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5536066/)






      share|improve this answer








      New contributor




      Phlya is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.






















        up vote
        8
        down vote













        A very interesting example are the cohesin molecules holding sister chromatids together in the oocytes (so only applicable to females, sorry!). Cohesion is established in utero, and these molecules are not recycled throughout life (AFAIK only shown directly for mice, not humans - https://www.ncbi.nlm.nih.gov/pubmed/20971813, https://www.ncbi.nlm.nih.gov/pubmed/26898469, but presumably same is true for us). This is considered to be a major contributor to the maternal age effect (https://en.wikipedia.org/wiki/Age_and_female_fertility) through low level loss of cohesion throughout life (since levels of cohesin can't be restored) until chromosomes start losing association between sisters which causes high chances of their missegregation (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5536066/)






        share|improve this answer








        New contributor




        Phlya is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
        Check out our Code of Conduct.




















          up vote
          8
          down vote










          up vote
          8
          down vote









          A very interesting example are the cohesin molecules holding sister chromatids together in the oocytes (so only applicable to females, sorry!). Cohesion is established in utero, and these molecules are not recycled throughout life (AFAIK only shown directly for mice, not humans - https://www.ncbi.nlm.nih.gov/pubmed/20971813, https://www.ncbi.nlm.nih.gov/pubmed/26898469, but presumably same is true for us). This is considered to be a major contributor to the maternal age effect (https://en.wikipedia.org/wiki/Age_and_female_fertility) through low level loss of cohesion throughout life (since levels of cohesin can't be restored) until chromosomes start losing association between sisters which causes high chances of their missegregation (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5536066/)






          share|improve this answer








          New contributor




          Phlya is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
          Check out our Code of Conduct.









          A very interesting example are the cohesin molecules holding sister chromatids together in the oocytes (so only applicable to females, sorry!). Cohesion is established in utero, and these molecules are not recycled throughout life (AFAIK only shown directly for mice, not humans - https://www.ncbi.nlm.nih.gov/pubmed/20971813, https://www.ncbi.nlm.nih.gov/pubmed/26898469, but presumably same is true for us). This is considered to be a major contributor to the maternal age effect (https://en.wikipedia.org/wiki/Age_and_female_fertility) through low level loss of cohesion throughout life (since levels of cohesin can't be restored) until chromosomes start losing association between sisters which causes high chances of their missegregation (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5536066/)







          share|improve this answer








          New contributor




          Phlya is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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          share|improve this answer



          share|improve this answer






          New contributor




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          answered 2 days ago









          Phlya

          1812




          1812




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          New contributor





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          Check out our Code of Conduct.






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          Check out our Code of Conduct.






















              up vote
              1
              down vote













              In terms of the common/abundant proteins, the answer would have to be elastin. The turnover is extremely slow, with a half-life of 74 years (https://www.elastagen.com/media/The_Science_of_Elastin.pdf) or "decades" according to other sources. In any case it is very slow - slow enough that most of it lasts a lifetime. It is a major constituent of the extracellular matrix but the rate of synthesis (and breakdown) is much slower than collagen (the other major structural protein). Reduced levels of elastin are one of the primary contributions to the aged look of older humans






              share|improve this answer

























                up vote
                1
                down vote













                In terms of the common/abundant proteins, the answer would have to be elastin. The turnover is extremely slow, with a half-life of 74 years (https://www.elastagen.com/media/The_Science_of_Elastin.pdf) or "decades" according to other sources. In any case it is very slow - slow enough that most of it lasts a lifetime. It is a major constituent of the extracellular matrix but the rate of synthesis (and breakdown) is much slower than collagen (the other major structural protein). Reduced levels of elastin are one of the primary contributions to the aged look of older humans






                share|improve this answer























                  up vote
                  1
                  down vote










                  up vote
                  1
                  down vote









                  In terms of the common/abundant proteins, the answer would have to be elastin. The turnover is extremely slow, with a half-life of 74 years (https://www.elastagen.com/media/The_Science_of_Elastin.pdf) or "decades" according to other sources. In any case it is very slow - slow enough that most of it lasts a lifetime. It is a major constituent of the extracellular matrix but the rate of synthesis (and breakdown) is much slower than collagen (the other major structural protein). Reduced levels of elastin are one of the primary contributions to the aged look of older humans






                  share|improve this answer












                  In terms of the common/abundant proteins, the answer would have to be elastin. The turnover is extremely slow, with a half-life of 74 years (https://www.elastagen.com/media/The_Science_of_Elastin.pdf) or "decades" according to other sources. In any case it is very slow - slow enough that most of it lasts a lifetime. It is a major constituent of the extracellular matrix but the rate of synthesis (and breakdown) is much slower than collagen (the other major structural protein). Reduced levels of elastin are one of the primary contributions to the aged look of older humans







                  share|improve this answer












                  share|improve this answer



                  share|improve this answer










                  answered yesterday









                  Alex I

                  21227




                  21227






















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