F1-ATPase of Escherichia coli: the ?- inhibited state forms after ATP hydrolysis, is distinct from the ADP-inhibited state, and responds dynamically to catalytic site ligands.

ABSTRACT: F1-ATPase is the catalytic complex of rotary nanomotor ATP synthases. Bacterial ATP synthases can be autoinhibited by the C-terminal domain of subunit ?, which partially inserts into the enzyme's central rotor cavity to block functional subunit rotation. Using a kinetic, optical assay of F1·? binding and dissociation, we show that formation of the extended, inhibitory conformation of ? (?X) initiates after ATP hydrolysis at the catalytic dwell step. Prehydrolysis conditions prevent formation of the ?X state, and post-hydrolysis conditions stabilize it. We also show that ? inhibition and ADP inhibition are distinct, competing processes that can follow the catalytic dwell. We show that the N-terminal domain of ? is responsible for initial binding to F1 and provides most of the binding energy. Without the C-terminal domain, partial inhibition by the ? N-terminal domain is due to enhanced ADP inhibition. The rapid effects of catalytic site ligands on conformational changes of F1-bound ? suggest dynamic conformational and rotational mobility in F1 that is paused near the catalytic dwell position.

SUBMITTER: Shah NB 

PROVIDER: S-EPMC3611008 | biostudies-literature | 2013 Mar

REPOSITORIES: biostudies-literature