DOES THE GAMMA-SUBUNIT MOVE TO AN ABORTIVE POSITION FOR ATP HYDROLYSIS WHEN THE F-1-CENTER-DOT-ADP-CENTER-DOT-MG COMPLEX ISOMERIZES TO THE INACTIVE F-1-ASTERISK-CENTER-DOT-ADP-CENTER-DOT-MG COMPLEX

F-1-ATPases transiently entrap inhibitory MgADP in a catalytic site du ring turnover when noncatalytic sites are not saturated with ATP. An i nitial burst of ATP hydrolysis rapidly decelerates to a slow intermedi ate rate that gradually accelerates to a final steady-state rate. Tran sition from the intermediate to the final rate is caused by slow bindi ng of ATP to noncatalytic sites which promotes dissociation of inhibit ory MgADP from the affected catalytic site. Evidence from several labo ratories suggests that the gamma subunit rotates with respect to alpha /beta subunit pairs of F-1-ATPases during ATP hydrolysis. The alpha(3) beta(3) and alpha(3) beta(3) delta subcomplexes of the TF1-ATPase do not entrap inhibitory MgADP in a catalytic site during turnover, sugge sting involvement of the gamma subunit in the entrapment process, From these observations, it is proposed that the gamma subunit moves into an abortive position for ATP hydrolysis when inhibitory MgADP is entra pped in a catalytic site during ATP hydrolysis.