ATP hydrolysis-driven H+ translocation is stimulated by sulfate, a strong inhibitor of mitochondrial ATP synthesis

ANABELLA F. LODEYRO; MARÍA V. CASTELLI; OSCAR A. ROVERI

JOURNAL OF BIOENERGETICS AND BIOMEMBRANES

Springer

Lugar: Holanda; Año: 2008 vol. 40 p. 269 - 279

0145-479X

Sulfate is a partial inhibitor at low and a nonessentialactivator at high [ATP] of the ATPase activity ofF1. Therefore, a catalytically-competent ternaryF1•ATP•sulfate complex can be formed. In addition, theANS fluorescence enhancement driven by ATP hydrolysisin submitochondrial particles is also stimulated by sulfate,clearly showing that the ATP hydrolysis in its presence iscoupled to H+ translocation. However, sulfate is a stronglinear inhibitor of the mitochondrial ATP synthesis. The inhibition was competitive (Ki=0.46 mM) with respect to Pi and mixed (Ki=0.60 and Ki prima=5.6 mM) towards ADP.Since it is likely that sulfate exerts its effects by binding atthe Pi binding subdomain of the catalytic site, we suggestthat the catalytic site involved in the H+ translocationdriven by ATP hydrolysis has a more open conformationthan the half-closed one (BHC), which is an intermediate inATP synthesis. Accordingly, ATP hydrolysis is not necessarilythe exact reversal of ATP synthesis.