Inhibition of the H+‐ATPase in bovine adrenal chromaffin granule ghosts by diethylstilbestrol Evidence for a tight coupling between ATP hydrolysis and proton translocation

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Abstract
Diethylstilbestrol (DES) was found to inhibit reversibly the hydrolysis of MgATP (80% at 100μM) and proton pump activity (I 50⋍15 μM, complete at 100 μM) in chromaffin granule ghosts. The parallel inhibition suggests a tight kinetic coupling between the two activities. The Mg2+-ATPase activity, but not proton pumping, was partially restored by N,N′-dicyclohexylcarbodiimide,indicating that the two inhibitors in combination cause a partial uncoupling. The non-competitive type of inhibition shows that the action of DES is distal to the site of ATP binding and hydrolysis. Although unspecific, the interaction of DES with the chromaffin granule membrane seems primarily to affect the H+-ATPase.

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