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
    Nov 30 at 0:16

  • 12

    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
    Nov 30 at 0:22

  • would there be a protein that is taken from the environment and cannot be produced inside the body? Like vitamins?
    – Ooker
    Nov 30 at 0:32

  • 1

    @Armatus Antibodies do not and cannot persist lifelong. They’re actually destroyed at a rather rapid rate.
    – forest
    Nov 30 at 3:23

up vote
50
down vote

favorite

5

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

  • 1

    Maternally contributed antibodies? They could be older than you if there are any that persist life-long.
    – Armatus
    Nov 30 at 0:16

  • 12

    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
    Nov 30 at 0:22

  • would there be a protein that is taken from the environment and cannot be produced inside the body? Like vitamins?
    – Ooker
    Nov 30 at 0:32

  • 1

    @Armatus Antibodies do not and cannot persist lifelong. They’re actually destroyed at a rather rapid rate.
    – forest
    Nov 30 at 3:23

up vote
50
down vote

favorite

5

up vote
50
down vote

favorite

5
5

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

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 Dec 1 at 1:30

Ben Crowell

56559

56559

asked Nov 28 at 23:05

JalfredP

35327

35327

  • 1

    Maternally contributed antibodies? They could be older than you if there are any that persist life-long.
    – Armatus
    Nov 30 at 0:16

  • 12

    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
    Nov 30 at 0:22

  • would there be a protein that is taken from the environment and cannot be produced inside the body? Like vitamins?
    – Ooker
    Nov 30 at 0:32

  • 1

    @Armatus Antibodies do not and cannot persist lifelong. They’re actually destroyed at a rather rapid rate.
    – forest
    Nov 30 at 3:23

  • 1

    Maternally contributed antibodies? They could be older than you if there are any that persist life-long.
    – Armatus
    Nov 30 at 0:16

  • 12

    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
    Nov 30 at 0:22

  • would there be a protein that is taken from the environment and cannot be produced inside the body? Like vitamins?
    – Ooker
    Nov 30 at 0:32

  • 1

    @Armatus Antibodies do not and cannot persist lifelong. They’re actually destroyed at a rather rapid rate.
    – forest
    Nov 30 at 3:23

1

1

Maternally contributed antibodies? They could be older than you if there are any that persist life-long.
– Armatus
Nov 30 at 0:16

Maternally contributed antibodies? They could be older than you if there are any that persist life-long.
– Armatus
Nov 30 at 0:16

12

12

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
Nov 30 at 0:22

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
Nov 30 at 0:22

would there be a protein that is taken from the environment and cannot be produced inside the body? Like vitamins?
– Ooker
Nov 30 at 0:32

would there be a protein that is taken from the environment and cannot be produced inside the body? Like vitamins?
– Ooker
Nov 30 at 0:32

1

1

@Armatus Antibodies do not and cannot persist lifelong. They’re actually destroyed at a rather rapid rate.
– forest
Nov 30 at 3:23

@Armatus Antibodies do not and cannot persist lifelong. They’re actually destroyed at a rather rapid rate.
– forest
Nov 30 at 3:23

4 Answers
4

active

oldest

votes

up vote
67
down vote

accepted

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.

Edit: A few references:

This article shows that one can use 14C radiodating to determine the date of synthesis of lens proteins, because of their exceptionally low turnover: Lynnerup, “Radiocarbon Dating of the Human Eye Lens Crystallines Reveal Proteins without Carbon Turnover throughout Life”, PLoS One (2008) 3:e1529

This excellent review suggested by iayork (thanks!) lists long-lived proteins (including crystallins) and how they were identified as such:
Toyama & Hetzer, “Protein homeostasis: live long, won’t prosper” Nat Rev Mol Cell Biol. (2013) 14:55–61

share|improve this answer

  • 13

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

  • I agree it is almost certainly in the eye, but why Crystallin specifically?
    – John
    Nov 29 at 23:56

  • 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
    Nov 30 at 13:29

up vote
22
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 😀 )
    – JalfredP
    Nov 29 at 19:32

  • I would be very surprised if ribosomes were not degraded. And proteosomes do get degraded.
    – forest
    Nov 30 at 3:25

up vote
9
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
    3
    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.

    Elastin 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). While breakdown is extremely slow, synthesis is even slower and may not be sufficient to replace the lost elastin, resulting in decreased levels with age. This is one of the primary contributions to the aged look of older humans

    share|improve this answer

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      4 Answers
      4

      active

      oldest

      votes

      4 Answers
      4

      active

      oldest

      votes

      active

      oldest

      votes

      active

      oldest

      votes

      up vote
      67
      down vote

      accepted

      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.

      Edit: A few references:

      This article shows that one can use 14C radiodating to determine the date of synthesis of lens proteins, because of their exceptionally low turnover: Lynnerup, “Radiocarbon Dating of the Human Eye Lens Crystallines Reveal Proteins without Carbon Turnover throughout Life”, PLoS One (2008) 3:e1529

      This excellent review suggested by iayork (thanks!) lists long-lived proteins (including crystallins) and how they were identified as such:
      Toyama & Hetzer, “Protein homeostasis: live long, won’t prosper” Nat Rev Mol Cell Biol. (2013) 14:55–61

      share|improve this answer

      • 13

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

      • I agree it is almost certainly in the eye, but why Crystallin specifically?
        – John
        Nov 29 at 23:56

      • 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
        Nov 30 at 13:29

      up vote
      67
      down vote

      accepted

      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.

      Edit: A few references:

      This article shows that one can use 14C radiodating to determine the date of synthesis of lens proteins, because of their exceptionally low turnover: Lynnerup, “Radiocarbon Dating of the Human Eye Lens Crystallines Reveal Proteins without Carbon Turnover throughout Life”, PLoS One (2008) 3:e1529

      This excellent review suggested by iayork (thanks!) lists long-lived proteins (including crystallins) and how they were identified as such:
      Toyama & Hetzer, “Protein homeostasis: live long, won’t prosper” Nat Rev Mol Cell Biol. (2013) 14:55–61

      share|improve this answer

      • 13

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

      • I agree it is almost certainly in the eye, but why Crystallin specifically?
        – John
        Nov 29 at 23:56

      • 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
        Nov 30 at 13:29

      up vote
      67
      down vote

      accepted

      up vote
      67
      down vote

      accepted

      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.

      Edit: A few references:

      This article shows that one can use 14C radiodating to determine the date of synthesis of lens proteins, because of their exceptionally low turnover: Lynnerup, “Radiocarbon Dating of the Human Eye Lens Crystallines Reveal Proteins without Carbon Turnover throughout Life”, PLoS One (2008) 3:e1529

      This excellent review suggested by iayork (thanks!) lists long-lived proteins (including crystallins) and how they were identified as such:
      Toyama & Hetzer, “Protein homeostasis: live long, won’t prosper” Nat Rev Mol Cell Biol. (2013) 14:55–61

      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.

      Edit: A few references:

      This article shows that one can use 14C radiodating to determine the date of synthesis of lens proteins, because of their exceptionally low turnover: Lynnerup, “Radiocarbon Dating of the Human Eye Lens Crystallines Reveal Proteins without Carbon Turnover throughout Life”, PLoS One (2008) 3:e1529

      This excellent review suggested by iayork (thanks!) lists long-lived proteins (including crystallins) and how they were identified as such:
      Toyama & Hetzer, “Protein homeostasis: live long, won’t prosper” Nat Rev Mol Cell Biol. (2013) 14:55–61

      share|improve this answer

      share|improve this answer

      share|improve this answer

      edited 2 days ago

      answered Nov 28 at 23:35

      Mowgli

      1,133312

      1,133312

      • 13

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

      • I agree it is almost certainly in the eye, but why Crystallin specifically?
        – John
        Nov 29 at 23:56

      • 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
        Nov 30 at 13:29

      • 13

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

      • I agree it is almost certainly in the eye, but why Crystallin specifically?
        – John
        Nov 29 at 23:56

      • 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
        Nov 30 at 13:29

      13

      13

      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

      I agree it is almost certainly in the eye, but why Crystallin specifically?
      – John
      Nov 29 at 23:56

      I agree it is almost certainly in the eye, but why Crystallin specifically?
      – John
      Nov 29 at 23:56

      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
      Nov 30 at 13:29

      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
      Nov 30 at 13:29

      up vote
      22
      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 😀 )
        – JalfredP
        Nov 29 at 19:32

      • I would be very surprised if ribosomes were not degraded. And proteosomes do get degraded.
        – forest
        Nov 30 at 3:25

      up vote
      22
      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 😀 )
        – JalfredP
        Nov 29 at 19:32

      • I would be very surprised if ribosomes were not degraded. And proteosomes do get degraded.
        – forest
        Nov 30 at 3:25

      up vote
      22
      down vote

      up vote
      22
      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

      1,5231834

      1,5231834

      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 😀 )
        – JalfredP
        Nov 29 at 19:32

      • I would be very surprised if ribosomes were not degraded. And proteosomes do get degraded.
        – forest
        Nov 30 at 3:25

      • 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 😀 )
        – JalfredP
        Nov 29 at 19:32

      • I would be very surprised if ribosomes were not degraded. And proteosomes do get degraded.
        – forest
        Nov 30 at 3:25

      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 😀 )
      – JalfredP
      Nov 29 at 19:32

      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 😀 )
      – JalfredP
      Nov 29 at 19:32

      I would be very surprised if ribosomes were not degraded. And proteosomes do get degraded.
      – forest
      Nov 30 at 3:25

      I would be very surprised if ribosomes were not degraded. And proteosomes do get degraded.
      – forest
      Nov 30 at 3:25

      up vote
      9
      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

        up vote
        9
        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

          up vote
          9
          down vote

          up vote
          9
          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

          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

          share|improve this answer

          share|improve this answer

          answered Nov 30 at 16:20

          Phlya

          1912

          1912

              up vote
              3
              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.

              Elastin 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). While breakdown is extremely slow, synthesis is even slower and may not be sufficient to replace the lost elastin, resulting in decreased levels with age. This is one of the primary contributions to the aged look of older humans

              share|improve this answer

                up vote
                3
                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.

                Elastin 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). While breakdown is extremely slow, synthesis is even slower and may not be sufficient to replace the lost elastin, resulting in decreased levels with age. This is one of the primary contributions to the aged look of older humans

                share|improve this answer

                  up vote
                  3
                  down vote

                  up vote
                  3
                  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.

                  Elastin 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). While breakdown is extremely slow, synthesis is even slower and may not be sufficient to replace the lost elastin, resulting in decreased levels with age. This is 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.

                  Elastin 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). While breakdown is extremely slow, synthesis is even slower and may not be sufficient to replace the lost elastin, resulting in decreased levels with age. This is one of the primary contributions to the aged look of older humans

                  share|improve this answer

                  share|improve this answer

                  share|improve this answer

                  edited 2 days ago

                  answered Dec 1 at 8:44

                  Alex I

                  23227

                  23227

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