Inhibition by Mercurial Reagents and Role of SH Groups of the Adenosine Triphosphatase from Escherichia coli 414 Membranes

Mercurials selectively inhibited Escherichia coli 414 ATPase (EC 3.6.1.3). Inhibition of the soluble ATPase (BF1) was greater than for the membrane-bound enzyme. The titration of 4 SH groups per mol BF1 with 0.05 mm-p-chloromercuri[14C]benzoate showed a good dose-response curve for the inhibition of basal ATPase but not for the trypsin-stimulated activity. Accessible SH groups did not seem to be related to the active site of the enzyme. Mercurials appeared to affect E. coli ATPase by inducing a molecular change in the holo-enzyme, followed by dissociation. One to two SH groups with different degrees of accessibility were located in the α and γ subunits of ATPase (BF1) but only one was located in the β subunit, irrespective of the concentration of p-chloromercuribenzoic acid, suggesting a structural role for SH groups in BF1.