Y. Kato-yamada et al., epsilon Subunit, an endogenous inhibitor of bacterial F-1-ATPase, also inhibits F0F1-ATPase, J BIOL CHEM, 274(48), 1999, pp. 33991-33994
Since the report by Sternweis and Smith (Sternweis, P. C., and Smith, J. B.
(1980) Biochemistry 19, 526-531), the epsilon subunit, an endogenous inhib
itor of bacterial F-1-ATPase, has long been thought not to inhibit activity
of the holo enzyme, F0F1-ATPase. However, we report here that the epsilon
subunit is exerting inhibition in F0F1-ATPase. We prepared a C-terminal hal
f-truncated epsilon subunit (epsilon(Delta C)) of the thermophilic Bacillus
PS3 F0F1-ATPase and reconstituted F-1- and F0F1-ATPase containing epsilon(
Delta C). Compared with F-1- and F0F1-ATPase containing intact epsilon, tho
se containing epsilon(Delta C) showed uninhibited activity; severalfold hig
her rate of ATP hydrolysis at low ATP concentration and the start of ATP hy
drolysis without an initial lag at high ATP concentration. The F0F1-ATPase
containing epsilon(Delta C) was capable of ATP-driven H+ pumping. The time-
course of pumping at low ATP concentration was faster than that by the F0F1
-ATPase containing intact epsilon. Thus, the comparison with noninhibitory
epsilon(Delta C) mutant shed light on the inhibitory role of the intact eps
ilon subunit in F0F1-ATPase.