Does the gamma subunit move to an abortive position of ATP hydrolysis when the F1.ADP.Mg complex isomerizes to the inactive F1*.ADP.Mg complex?
F1-ATPases transiently entrap inhibitory MgADP in a catalytic site during turnover when noncatalytic sites are not saturated with ATP. An initial burst of ATP hydrolysis rapidly decelerates to a slow intermediate rate that gradually accelerates to a final steady-state rate. Transition from the intermediate to the final rate is caused by slow binding of ATP to noncatalytic sites which promotes dissociation of inhibitory MgADP from the affected catalytic site. Evidence from several laboratories suggests that the gamma subunit rotates with respect to alpha/beta subunit pairs of F1-ATPase 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, suggesting 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 entrapped in a catalytic site during ATP hydrolysis.
Allison
W S
WS
Department of Chemistry and Biochemistry, School of Medicine, University of California at San Diego, La Jolla 92093-0601, USA.
Jault
J M
JM
Dou
C
C
Grodsky
N B
NB
D000244:Adenosine Diphosphate / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase / Q000737:chemistry* / Q000378:metabolism*; D002384:Catalysis; D006868:Hydrolysis; D006180:Proton-Translocating ATPases / Q000737:chemistry* / Q000378:metabolism*; D013237:Stereoisomerism
D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D017301:Ca(2+) Mg(2+)-ATPase; D006180:Proton-Translocating ATPases