Na+-coupled alternative to H+-coupled primary transport systems in bacteria

✍ Scribed by Peter Dimroth

• Book ID: 102759697
• Publisher: John Wiley and Sons
• Year: 1991
• Tongue: English
• Weight: 727 KB
• Volume: 13
• Category: Article
• ISSN: 0265-9247
• DOI: 10.1002/bies.950130906

✦ Synopsis

Abstract

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.