Na(+)-coupled alternative to H(+)-coupled primary transport systems in bacteria.
Protons are the most common coupling ions in bacterial energy conversions. However, while many organisms, such as the alkaliphilic Bacilli, employ H(+)-bioenergetics for electron transport phosphorylation, they use Na+ as the coupling ion for transport and flagellar movement. The Na+ gradient required for these bioenergetic functions is established by the secondary Na+/H+ antiporter. In contrast, Vibrio alginolyticus and methanogenic bacteria have primary pumps for both H+ and Na+. They use the proton gradient for ATP synthesis while other, less energy-consuming membrane reactions are powered by the Na+ gradient. In a third mode, some anaerobic bacteria possess decarboxylases acting as primary Na+ pumps. For instance, in Klebsiella pneumoniae, the Na+ gradient established by oxaloacetate decarboxylase is used for the uptake of the growth substrate citrate, and Propionigenium modestum consumes the energy of the Na+ gradient formed by methylmalonyl-CoA decarboxylase directly for ATP synthesis.
Dimroth
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Mikrobiologisches Institut, Eidgenössische Technische Hochschule, ETH-Zentrum, Zürich, Switzerland.
D000255:Adenosine Triphosphate / Q000096:biosynthesis; D000332:Aerobiosis; D000693:Anaerobiosis; D001419:Bacteria / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism; D004579:Electron Transport; D004734:Energy Metabolism; D005407:Flagella / Q000502:physiology; D008564:Membrane Potentials; D008565:Membrane Proteins / Q000378:metabolism*; D008954:Models, Biological; D010085:Oxidative Phosphorylation; D010086:Oxidative Phosphorylation Coupling Factors; D011188:Potassium / Q000378:metabolism; D006180:Proton-Translocating ATPases / Q000378:metabolism; D011522:Protons; D012964:Sodium / Q000378:metabolism*; D017923:Sodium-Hydrogen Exchangers; D000254:Sodium-Potassium-Exchanging ATPase / Q000502:physiology*
D001426:Bacterial Proteins; D002352:Carrier Proteins; D008565:Membrane Proteins; D010086:Oxidative Phosphorylation Coupling Factors; D011522:Protons; D017923:Sodium-Hydrogen Exchangers; D000255:Adenosine Triphosphate; D012964:Sodium; D006180:Proton-Translocating ATPases; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium