The past and present of sodium energetics: May the sodium-motive force be with you

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, po...

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Published in:Biochimica et biophysica acta 2008-07, Vol.1777 (7-8), p.985-992
Main Authors: Mulkidjanian, Armen Y., Dibrov, Pavel, Galperin, Michael Y.
Format: Article
Language:English
Subjects:
Adenosine Triphosphatases - chemistry
Adenosine Triphosphatases - metabolism
Anaerobic pathogenic bacteria
ATP synthase
Binding Sites
Biological membranes
Biological Transport, Active
Chlamydia sp
Energy Metabolism
Models, Molecular
Nanomotors
Protein Conformation
Protein Subunits - chemistry
Protein Subunits - metabolism
Proton transfer
Proton-Translocating ATPases - metabolism
Sodium - metabolism
Sodium energetics
Sodium-dependent transporters
Sodium-motive force
Vacuolar Proton-Translocating ATPases - chemistry
Vacuolar Proton-Translocating ATPases - metabolism
Vibrio cholerae
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Summary: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.
ISSN:0005-2728
0006-3002
1879-2650
DOI:10.1016/j.bbabio.2008.04.028