Allison W S, Jault J M, Dou C, Grodsky N B
Department of Chemistry and Biochemistry, School of Medicine, University of California at San Diego, La Jolla 92093-0601, USA.
J Bioenerg Biomembr. 1996 Oct;28(5):433-8. doi: 10.1007/BF02113985.
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.
当非催化位点未被ATP饱和时，F1 - ATP酶在周转过程中会在催化位点短暂截留抑制性MgADP。ATP水解的初始爆发迅速减速至缓慢的中间速率，该速率随后逐渐加速至最终的稳态速率。从中间速率到最终速率的转变是由ATP缓慢结合到非催化位点引起的，这促进了抑制性MgADP从受影响的催化位点解离。几个实验室的证据表明，在ATP水解过程中，γ亚基相对于F1 - ATP酶的α/β亚基对发生旋转。TF1 - ATP酶的α3β3和α3β3δ亚复合物在周转过程中不会在催化位点截留抑制性MgADP，这表明γ亚基参与了截留过程。基于这些观察结果，有人提出，当在ATP水解过程中抑制性MgADP被困在催化位点时，γ亚基会移动到ATP水解的无效位置。
