Membrane-linked energy transductions. Bioenergetic functions of sodium: H+ is not unique as a coupling ion.
The concept is developed according to which Na+, like H+, can play the role of a coupling ion in energy-transducing biomembranes. This idea is based on observations that (i) Na+ can be extruded from the cell by primary pumps (Na-motive NADH-quinone reductase, decarboxylase or ATPase), and (ii) the downhill Na+ flux into the cell can be coupled with the performance of all the three types of membrane-linked work i.e. chemical (ATP synthesis), osmotic (accumulation of solutes) and mechanical (motility). Marine alkalotolerant Vibrio alginolyticus represents the first example of such a complete sodium cycle pattern. Simplified versions of the sodium cycle or some of its constituents are found in the cytoplasmic membrane of a great variety of taxa including anaerobic, aerobic and photosynthetic bacteria, cyanobacteria and animals; this fact indicates that Na+ energetics should be regarded as a common case, rather than a rare exception applied to some natural niches only.
Skulachev
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D000255:Adenosine Triphosphate / Q000096:biosynthesis; D000332:Aerobiosis; D000693:Anaerobiosis; D001419:Bacteria / Q000378:metabolism; D005075:Biological Evolution; D001693:Biological Transport, Active; D002462:Cell Membrane / Q000378:metabolism*; D004734:Energy Metabolism; D006868:Hydrolysis; D008954:Models, Biological; D009243:NAD / Q000378:metabolism; D010084:Oxidation-Reduction; D010788:Photosynthesis; D011188:Potassium / Q000502:physiology; D006180:Proton-Translocating ATPases / Q000378:metabolism; D011522:Protons; D012964:Sodium / Q000502:physiology*; D014733:Vibrio / Q000378:metabolism
D011522:Protons; D009243:NAD; D000255:Adenosine Triphosphate; D012964:Sodium; D006180:Proton-Translocating ATPases; D011188:Potassium