The past and present of sodium energetics: May the sodium-motive force be with you
- 作者：Armen Y. Mulkidjanian ; Pavel Dibrov ; Michael Y. Galperin
- 关键词：Sodium energetics ; Sodium-motive force ; ATP synthase ; Nanomotors ; Proton transfer ; Sodium-dependent transporters ; Biological membranes ; Vibrio cholerae ; Chlamydia sp. ; Anaerobic pathogenic bacteria
- 刊名：Biochimica et Biophysica Acta (BBA)/Bioenergetics
- 出版年：2008
- 期刊代码：13_00052728
- 类别：bio
- 出版时间：July-August 2008
- 卷：1777
- 期：7-8
- 页码：985-992
- 文件大小：526 K
摘要
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.