Hydrolysis and synthesis of ATP by membrane-bound ATPase from a motile Streptococcus |
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Authors: | C van der Drift D B Janssen P M G F van Wezenbeek |
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Institution: | (1) Department of Microbiology, Faculty of Science, University of Nijmegen, Nijmegen, The Netherlands |
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Abstract: | ATPase was detected in the membranes of a motile Streptococcus. Maximal enzymic activity was observed at pH 8 and ATP/Mg2+ ratio of 2. Mn2+ and Ca2+ could replace Mg2+ 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 and the electrochemical proton gradient showed that the data found are in agreement with a stoichiometry of 2 protons translocated per molecule ATP synthesized.Abbreviations
electrochemical gradient of protons
- DMO
5,5-dimethyl-2,4-oxazolidinedione
- CCCP
carbonylcyanide m-chlorophenylhydrazone
- FCCP
carbonylcyanide p-trifluoromethoxyphenylhydrazone
- DCCD
N,N-dicyclohexylcarbodiimide
- DNP
2,4-dimitrophenol |
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Keywords: | Motile Streptococcus Membrane-bound ATPase DCCD Valinomycin Uncouplers Protonmotive force ATP synthesis |
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