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Nat Struct Mol Biol. 2007 May;14(5):427-31. Epub 2007 Apr 29.

Structural basis of Na(+)/K(+)-ATPase adaptation to marine environments.

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Institute of Neurobiology, University of Puerto Rico-Medical Sciences Campus, San Juan, Puerto Rico 00901.


Throughout evolution, enzymes have adapted to perform in different environments. The Na(+)/K(+) pump, an enzyme crucial for maintaining ionic gradients across cell membranes, is strongly influenced by the ionic environment. In vertebrates, the pump sees much less external Na(+) (100-160 mM) than it does in osmoconformers such as squid (450 mM), which live in seawater. If the extracellular architecture of the squid pump were identical to that of vertebrates, then at the resting potential, the pump's function would be severely compromised because the negative voltage would drive Na(+) ions back to their binding sites, practically abolishing forward transport. Here we show that four amino acids that ring the external mouth of the ion translocation pathway are more positive in squid, thereby reducing the pump's sensitivity to external Na(+) and explaining how it can perform optimally in the marine environment.

[Indexed for MEDLINE]

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