Extremophile: Difference between revisions

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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 mammialian 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 to sequence - as well as eletrophoresis of the protein, 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 mammals tissue. But whales and other aquatic mammals far exceed this solubility limit - whales have 70 mg/g - and this overcoming the solubility contrains may be traced back to an increase in the net charge of myoglobin - from around +2 in terrestrial animals to around +4 in aquatic animlals.

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 determine that body mass ~~has~~ also ~~been~~ a critical contribution to ~~enabling~~ breath ~~holding~~, with the overall equation for the contribution of body mass and myoglobin net charge as follows:

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 determine 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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The ability of increasing net charge to enable higher solubility is a known phenomena<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.

Whales and elephants are both large animals that take life slow - walking slow, singing slow. But whales swim underwater while holding their breaths for long periods of time, and elephants can not: ''Why can whales hold their breaths for long, and elephants can not?'' One clue to this discrepancy is the difference in concentrations of myoglobin in whale and elephant muscle tissue: ''More myoglobin means more oxygen storage capacity'', and whales have over ''15 times'' the concentration of myoglobin as elephants do (''70 mg/g'' wet mass compared to the elephants ''4.6''). But this leads to a biophysical question.

A very high concentration of myoglobin should lead to aggregation, which would prevent myoglobin from functioning, so ''how do whales' myoglobin deal with this extreme demand, and why can't elephants' myoglobin accumulate to high concentrations as well?'' In a recent article in ''Science''<ref name="whaleMyo"> DOI:10.1126/science.1234192</ref>, the laboratories of Professors Berenbrink, Campbell, and Cossins demonstrate that ''natural variation in net positive charge explains aquatic and terrestrial animals' different diving abilities''. Following this pattern, whale myoglobin has a net charge ''two formal charges higher'' than in elephants: ''+4 compared to +2'' in the elephant. Apparently a protein's solubility is a function of its net charge<ref>PMID: 14741208 </ref>, where ''a protein with a higher net charge is much more soluble''.

It comes down to <scene name='55/557585/Align_test/18'>eight divergent amino acids (elephant's amino acids in yellow halos)</scene>. Without these 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>.

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@@ Line 7: / Line 7: @@
 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 mammialian 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 to sequence - as well as eletrophoresis of the protein, 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 mammals tissue. But whales and other aquatic mammals far exceed this solubility limit - whales have 70 mg/g - and this overcoming the solubility contrains may be traced back to an increase in the net charge of myoglobin - from around +2 in terrestrial animals to around +4 in aquatic animlals.
-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 determine that body mass has also been a critical contribution to enabling breath holding, with the overall equation for the contribution of body mass and myoglobin net charge as follows:
+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 determine 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
@@ Line 14: / Line 14: @@
 The ability of increasing net charge to enable higher solubility is a known phenomena<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.
-Whales and elephants are both large animals that take life slow - walking slow, singing slow. But whales swim underwater while holding their breaths for long periods of time, and elephants can not: ''Why can whales hold their breaths for long, and elephants can not?'' One clue to this discrepancy is the difference in concentrations of myoglobin in whale and elephant muscle tissue: ''More myoglobin means more oxygen storage capacity'', and whales have over ''15 times'' the concentration of myoglobin as elephants do (''70 mg/g'' wet mass compared to the elephants ''4.6''). But this leads to a biophysical question.
-A very high concentration of myoglobin should lead to aggregation, which would prevent myoglobin from functioning, so ''how do whales' myoglobin deal with this extreme demand, and why can't elephants' myoglobin accumulate to high concentrations as well?'' In a recent article in ''Science''<ref name="whaleMyo"> DOI:10.1126/science.1234192</ref>, the laboratories of Professors Berenbrink, Campbell, and Cossins demonstrate that ''natural variation in net positive charge explains aquatic and terrestrial animals' different diving abilities''. Following this pattern, whale myoglobin has a net charge ''two formal charges higher'' than in elephants: ''+4 compared to +2'' in the elephant. Apparently a protein's solubility is a function of its net charge<ref>PMID: 14741208 </ref>, where ''a protein with a higher net charge is much more soluble''.
 It comes down to <scene name='55/557585/Align_test/18'>eight divergent amino acids (elephant's amino acids in yellow halos)</scene>. Without these 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>.