A reciprocating motion-driven rotation mechanism for the ATP synthase

摘要

The ATP synthase (having a typical subunit composition of α₃β₃γδεab₂c_8-15) employs an intriguing rotary mechanism for the generation of ATP from ADP and P_i, using energy stored in a transmembrane proton gradient. The conventional rotary model, although being generally accepted, remains difficult to explain certain experimental observations. Here we propose an alternative rotary model for the ATP synthase such that what rotates is the catalytic α₃β₃ cylinder rather than the central stalk and the membrane-embedded c-ring. Specifically, the membrane translocation of protons would induce a cycled conformational change in the c-ring, leading to a reciprocating motion of the attached central stalk, which in turn drives the unidirectional rotation of the α₃β₃ cylinder. Such a reciprocating motion-driven rotation mechanism is somehow analogous to the working mechanism of a retractable click ballpoint pen. Our new model not only explains the experimental observations that have been difficult to reconcile with the conventional model but also avoids its theoretical illogicality.