Authors: Anabella F Lodeyro María V Castelli Oscar A Roveri
Publish Date: 2008/10/10
Volume: 40, Issue: 4, Pages: 269-
Abstract
Sulfate is a partial inhibitor at low and a nonessential activator at high ATP of the ATPase activity of F1 Therefore a catalyticallycompetent ternary F1•ATP•sulfate complex can be formed In addition the ANS fluorescence enhancement driven by ATP hydrolysis in submitochondrial particles is also stimulated by sulfate clearly showing that the ATP hydrolysis in its presence is coupled to H+ translocation However sulfate is a strong linear inhibitor of the mitochondrial ATP synthesis The inhibition was competitive K i=046 mM with respect to Pi and mixed K i=060 and K′i=56 mM towards ADP Since it is likely that sulfate exerts its effects by binding at the Pi binding subdomain of the catalytic site we suggest that the catalytic site involved in the H+ translocation driven by ATP hydrolysis has a more open conformation than the halfclosed one βHC which is an intermediate in ATP synthesis Accordingly ATP hydrolysis is not necessarily the exact reversal of ATP synthesis
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