Hydrolysis and synthesis of ATP by membrane-bound ATPase from a motileStreptococcus

✍ Scribed by C. Drift; D. B. Janssen; P. M. G. F. Wezenbeek

• Publisher: Springer
• Year: 1978
• Tongue: English
• Weight: 544 KB
• Volume: 119
• Category: Article
• ISSN: 0302-8933
• DOI: 10.1007/bf00407924

✦ Synopsis

ATPase was detected in the membranes of a motile Streptococcus. Maximal enzymic activity was observed at pH 8 and ATP/Mg 2 § ratio of 2. Mn 2 + and Ca 2 § could replace Mg 2 + to some extent. Besides ATP, GTP and ITP were substrates. The enzyme was inhibited by N,N'-dicyclohexylcarbodiimide but not by sodium azide, uncouplers or bathophenanthroline.

An electrochemical gradient of protons, which was artificially imposed across the membranes of Streptococcus cells by manipulation of either the K + diffusion potential or the transmembrane pH gradient, led to ATP synthesis. ATP synthesis was abolished by proton conductors, an inhibitor of the ATPase or an increase in the extracellular K + concentration. A comparison between the phosphate potential a n d the electrochemical proton gradient showed that the data found are in agreement with a stoichiometry of 2 protons translocated per molecule ATP synthesized.