Extremophile
From Proteopedia
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== Positively charged myoglobin allows whales to hold their breath during long dives == | == Positively charged myoglobin allows whales to hold their breath during long dives == | ||
| - | Elephants can hold their breath for 2 minutes, but whales can hold their breath for 60 minutes - and they do, migrating underwater around the world. To get a clue as to why whales can hold their breath for so long, several researchers attained tissue samples from hundreds of aquatic and terrestrial mammalian species (mainly from museum collections)<ref name="whaleMyo"> DOI:10.1126/science.1234192</ref>. They measured the concentration of [[myoglobin]], the protein that stores oxygen in muscle tissue for times of muscle activity, and also sequenced each specie's myoglobin gene, and used this sequence - as well as | + | Elephants can hold their breath for 2 minutes, but whales can hold their breath for 60 minutes - and they do, migrating underwater around the world. To get a clue as to why whales can hold their breath for so long, several researchers attained tissue samples from hundreds of aquatic and terrestrial mammalian species (mainly from museum collections)<ref name="whaleMyo"> DOI:10.1126/science.1234192</ref>. They measured the concentration of [[myoglobin]], the protein that stores oxygen in muscle tissue for times of muscle activity, and also sequenced each specie's myoglobin gene, and used this sequence - as well as the protein's mobility on a native gel (which depends soley on structure and charge - with myoglobin from different species all having the same structure), when possible - to calculate the net charge of each myoglobin protein. |
Amazingly, they found that independently, aquatic mammals across the mammalian phylogeny had acquired their ability to hold their breath, by increasing the concentration of myoglobin, through increasing the net charge of myoglobin. In real values, typically, terrestrial mammal's myoglobin has a solubility of 20 mg/g tissue ([[http://www.sigmaaldrich.com/content/dam/sigma-aldrich/docs/Sigma/Product_Information_Sheet/2/m0630pis.pdf Sigma Aldrich]]) and that is the level of myoglobin found in most terrestrial mammal's tissue. But whales and other aquatic mammals far exceed this solubility limit - whales have 70 mg/g - and this overcoming the solubility constraint may be traced back to an increase in the net charge of myoglobin - from around +2 in terrestrial animals to around +4 in aquatic animals. | Amazingly, they found that independently, aquatic mammals across the mammalian phylogeny had acquired their ability to hold their breath, by increasing the concentration of myoglobin, through increasing the net charge of myoglobin. In real values, typically, terrestrial mammal's myoglobin has a solubility of 20 mg/g tissue ([[http://www.sigmaaldrich.com/content/dam/sigma-aldrich/docs/Sigma/Product_Information_Sheet/2/m0630pis.pdf Sigma Aldrich]]) and that is the level of myoglobin found in most terrestrial mammal's tissue. But whales and other aquatic mammals far exceed this solubility limit - whales have 70 mg/g - and this overcoming the solubility constraint may be traced back to an increase in the net charge of myoglobin - from around +2 in terrestrial animals to around +4 in aquatic animals. | ||
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<StructureSection load='1mbn' size='350' side='right' caption='myoglobin (PDB entry [[1mbn]])' scene='55/557585/Align_test/5'> | <StructureSection load='1mbn' size='350' side='right' caption='myoglobin (PDB entry [[1mbn]])' scene='55/557585/Align_test/5'> | ||
==Molecular Tour== | ==Molecular Tour== | ||
| - | The ability of increasing net charge to enable higher solubility is a known | + | The ability of increasing net charge to enable higher solubility is a known phenomenon<ref>doi: 10.1073/pnas.0402797101</ref>, and this study is consistent with previous reports<ref>PMID: 14741208 </ref>. The aquatic animals have increased their net charge in a variety of ways - different combinations of amino acids switches. We present one such manifestation of this overall trend, by comparing the elephant and whale myoglobin structures. |
It comes down to <scene name='55/557585/Align_test/18'>eight divergent amino acids (elephant's amino acids in yellow halos, and whale's amino acids without yellow halos, next to each other)</scene> that affect that charge - out of a total of 27 divergent amino acids. Without these eight differently charged amino acids, myoglobin in both whale and elephants has a charge of ''+1''. With them, whale myoglobin has a net charge of ''+4'' and elephants of ''+2''. Importantly, all eight of these divergent amino acids are <scene name='52/523344/Elephantwhale/34'>surface residues</scene>. | It comes down to <scene name='55/557585/Align_test/18'>eight divergent amino acids (elephant's amino acids in yellow halos, and whale's amino acids without yellow halos, next to each other)</scene> that affect that charge - out of a total of 27 divergent amino acids. Without these eight differently charged amino acids, myoglobin in both whale and elephants has a charge of ''+1''. With them, whale myoglobin has a net charge of ''+4'' and elephants of ''+2''. Importantly, all eight of these divergent amino acids are <scene name='52/523344/Elephantwhale/34'>surface residues</scene>. | ||
Revision as of 15:58, 1 January 2014
Extraordinary Proteins
Life has managed to weather extreme environments - almost every hole we've poked a stick into contains thriving living communities. Proteins are a necessity for living, and therefore tuning protein structures to an extreme environment is of paramount value to an evolving organism. In this article, we present the biophysical modifications present in extreme protein structures.
Positively charged myoglobin allows whales to hold their breath during long dives
Elephants can hold their breath for 2 minutes, but whales can hold their breath for 60 minutes - and they do, migrating underwater around the world. To get a clue as to why whales can hold their breath for so long, several researchers attained tissue samples from hundreds of aquatic and terrestrial mammalian species (mainly from museum collections)[1]. They measured the concentration of myoglobin, the protein that stores oxygen in muscle tissue for times of muscle activity, and also sequenced each specie's myoglobin gene, and used this sequence - as well as the protein's mobility on a native gel (which depends soley on structure and charge - with myoglobin from different species all having the same structure), when possible - to calculate the net charge of each myoglobin protein.
Amazingly, they found that independently, aquatic mammals across the mammalian phylogeny had acquired their ability to hold their breath, by increasing the concentration of myoglobin, through increasing the net charge of myoglobin. In real values, typically, terrestrial mammal's myoglobin has a solubility of 20 mg/g tissue ([Sigma Aldrich]) and that is the level of myoglobin found in most terrestrial mammal's tissue. But whales and other aquatic mammals far exceed this solubility limit - whales have 70 mg/g - and this overcoming the solubility constraint may be traced back to an increase in the net charge of myoglobin - from around +2 in terrestrial animals to around +4 in aquatic animals.
However, a 3-fold increase in concentration of myoglobin ought to result in a similar fold increase in max time of breath holding, and the researchers show that body mass also makes a critical contribution to an animal's ability to hold its breath, with the overall equation for the contribution of body mass and myoglobin net charge as follows:
log (maximum time underwater) = 0.223*log(body mass) + 0.972*log(myoglobin net charge) + 0.891
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- ↑ 1.0 1.1 Mirceta S, Signore AV, Burns JM, Cossins AR, Campbell KL, Berenbrink M. Evolution of mammalian diving capacity traced by myoglobin net surface charge. Science. 2013 Jun 14;340(6138):1234192. doi: 10.1126/science.1234192. PMID:23766330 doi:http://dx.doi.org/10.1126/science.1234192
- ↑ Brocchieri L. Environmental signatures in proteome properties. Proc Natl Acad Sci U S A. 2004 Jun 1;101(22):8257-8. Epub 2004 May 24. PMID:15159533 doi:http://dx.doi.org/10.1073/pnas.0402797101
- ↑ Goh CS, Lan N, Douglas SM, Wu B, Echols N, Smith A, Milburn D, Montelione GT, Zhao H, Gerstein M. Mining the structural genomics pipeline: identification of protein properties that affect high-throughput experimental analysis. J Mol Biol. 2004 Feb 6;336(1):115-30. PMID:14741208 doi:http://dx.doi.org/10.1016/S0022283603014748
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