The neurospora plasma membrane ATPase is an electrogenic pump.

Abstract

The electrical potential across the Neurospora [crassa] plasma membrane, as monitored by [14C]SCN- uptake by isolated Neurospora plasma membrane vesicles, was markedly increased (interior positive) under conditions of ATP hydrolysis catalyzed by the plasma membrane ATPase. [14C]SCN- uptake by the vesicles was minimal in the presence of Tris phosphate, Tris phosphate plus Mg+2, Tris ADP plus Mg+2, and Tris ATP, but was markedly stimulated in the presence of Tris ATP plus Mg+2. Mg+2-ATP stimulated [14C]SCN- uptake displayed a Mg+2-ATP concentration dependence identical to that for ATP hydrolysis by the plasma membrane ATPase, and was markedly depressed in the presence of the proton conductors sodium azide and carbonyl cyanide m-chlorophenylhydrazone. ANS (1-anilino naphthalene-8-sulfonic acid) fluorescence was enhanced upon addition of Mg+2-ATP to the vesicles, and the fluorescence enhancement was abolished in the presence of sodium azide. ATP hydrolysis, catalyzed by the Neurospora plasma membrane ATPase, probably results in the generation of a transmembrane electrical potential.