Editors' ChoiceBiochemistry

High-Salt Survival Tactics

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Science's STKE  14 Aug 2007:
Vol. 2007, Issue 399, pp. tw296
DOI: 10.1126/stke.3992007tw296

The Na+/H+ antiporter NhaA is an inner-membrane protein in Escherichia coli that is required for survival in high salt or under alkaline stress. NhaA uses energy from proton transport down an electrochemical gradient into the cell to excrete Na+, but not K+, from the cytoplasm. Starting from a recently determined structure of NhaA, Arkin et al. performed molecular dynamics simulations to examine the mechanism of ion transport, pH regulation, and cation selectivity. The simulations, together with existing experimental data and mutagenesis experiments, indicate that three aspartates are essential to NhaA function: Asp164 is the Na+ binding site, Asp163 controls alternating cytoplasmic or periplasmic access to the binding site, and Asp133 is involved in pH regulation.

I. T. Arkin, H. Xu, M. Ø. Jensen, E. Arbely, E. R. Bennett, K. J. Bowers, E. Chow, R. O. Dror, M. P. Eastwood, R. Flitman-Tene, B. A. Gregersen, J. L. Klepeis, I. Kolossváry, Y. Shan, D. E. Shaw, Mechanism of Na+/H+ antiporting. Science 317, 799-803 (2007). [Abstract] [Full Text]