Molecular dynamics simulations of yeast F1-ATPase before and after 16° rotation of the γ subunit.

We have recently proposed the "packing exchange mechanism" for F1-ATPase, wherein the perturbation by a substrate binding/release or an ATP hydrolysis is followed by the reorganization of the asymmetric packing structure of the α3β3 complex, accompanying the γ subunit rotation. As part of a further investigation of this rotational mechanism, we performed all-atom molecular dynamics simulations for yeast F1-ATPase both before and after a 16° rotation of the γ subunit triggered by a Pi release. We analyzed the structural fluctuations, the subunit interface interactions, and the dynamics of the relative subunit arrangements before and after the rotation. We found that with the Pi release the αEβE subunit interface becomes looser, which also allosterically makes the αDPβDP subunit interface looser. This structural communication between these interfaces takes place through a tightening of the αTPβTP subunit interface. The γ subunit interacts less strongly with αDP and βDP and more strongly with αTP and βTP. After the Pi release, the tightly packed interfaces are reorganized from the interfaces around βDP to those around βTP, inducing the 16° rotation. These results, which are consistent with the packing exchange mechanism, allow us to deduce a view of the structural change during the 40° rotation.