Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
8299224 | Biochimica et Biophysica Acta (BBA) - Bioenergetics | 2008 | 8 Pages |
Abstract
All living cells routinely expel Na+ ions, maintaining lower concentration of Na+ in the cytoplasm than in the surrounding milieu. In the vast majority of bacteria, as well as in mitochondria and chloroplasts, export of Na+ occurs at the expense of the proton-motive force. Some bacteria, however, possess primary generators of the transmembrane electrochemical gradient of Na+ (sodium-motive force). These primary Na+ pumps have been traditionally seen as adaptations to high external pH or to high temperature. Subsequent studies revealed, however, the mechanisms for primary sodium pumping in a variety of non-extremophiles, such as marine bacteria and certain bacterial pathogens. Further, many alkaliphiles and hyperthermophiles were shown to rely on H+, not Na+, as the coupling ion. We review here the recent progress in understanding the role of sodium-motive force, including (i) the conclusion on evolutionary primacy of the sodium-motive force as energy intermediate, (ii) the mechanisms, evolutionary advantages and limitations of switching from Na+ to H+ as the coupling ion, and (iii) the possible reasons why certain pathogenic bacteria still rely on the sodium-motive force.
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Authors
Armen Y. Mulkidjanian, Pavel Dibrov, Michael Y. Galperin,