Membrane-Bound Adenosine Triphosphatase of Escherichia coli

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Abstract
Sodium azide and diphenyl phosphorazidate (DPPA) inhibited purified membrane-bound ATPase [coupling factor of oxidative phosphorylation; EC 3.6.1.3] of Escherichia coli noncompetitively with K1 values of 39 and 51 μM, respectively. Sodium azide and DPPA inhibited the activity of ATPase bound to the membrane as effectively as that of the purified enzyme. 3) The effects of sodium azide on succinate-dependent ATP synthesis, P exchange, and ATP hydrolysis reactions by the membrane vesicles were compared under the same conditions. At concentrations below 1.0 m sodium azide inhibited ATP hydrolysis, but P1-ATP exchange and ATP synthesis were almost unaffected. At 10 mM sodium azide, both P1-ATP exchange and ATP synthesis reactions were completely inhibited, probably because at this concentration, sodium azide acted as a proton-conducting uncoupler.