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Hydrolysis and synthesis of ATP by membrane-bound ATPase from a motile Streptococcus
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.
Insights
Researchers identified an ATPase enzyme in Streptococcus membranes, crucial for energy production. This enzyme utilizes proton gradients to synthesize ATP, with a stoichiometry of 2 protons per ATP molecule.
Area of Science:
- Microbiology
- Biochemistry
- Cellular Biology
Background:
- Motile Streptococcus species possess membrane-bound enzymes involved in energy metabolism.
- Understanding the mechanisms of ATP synthesis in bacteria is vital for cellular function and potential therapeutic targets.
Purpose of the Study:
- To characterize the properties of an ATPase enzyme found in Streptococcus membranes.
- To investigate the role of this ATPase in ATP synthesis driven by an electrochemical proton gradient.
Main Methods:
- Enzyme activity assays were performed at varying pH and ion concentrations.
- ATP synthesis was induced by artificial electrochemical proton gradients.
- Inhibitor studies were conducted using specific chemical agents.
Main Results:
- The Streptococcus ATPase exhibited maximal activity at pH 8 and demonstrated substrate specificity for ATP, GTP, and ITP.
- The enzyme was sensitive to N,N'-dicyclohexylcarbodiimide but resistant to sodium azide and uncouplers.
- Artificial proton gradients successfully drove ATP synthesis, which was inhibited by proton conductors and ATPase inhibitors.
Conclusions:
- The identified ATPase is involved in proton-motive force-driven ATP synthesis in Streptococcus.
- The stoichiometry of proton translocation to ATP synthesis is approximately 2:1.
- These findings contribute to understanding bacterial energy transduction mechanisms.