Abstract
The ATP synthase (having a typical subunit composition of α3β3γδεab2c8-15) employs an intriguing rotary mechanism for the generation of ATP from ADP and Pi, 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.
Highlights
The ATP synthase, being recognized as the principle energy transformer in living organisms, is a membrane-integrated multi-subunit protein complex (von Ballmoos et al, 2009)
It catalyzes the synthesis of ATP from ADP and Pi by utilizing the electrochemical potential energy stored in a transmembrane proton gradient (Mitchell, 1961)
According to the current view of this mechanism, the membrane-embedded c-ring is driven to rotate unidirectionally by the downhill proton translocation along a channel formed between the a-subunit and the c-ring (Duncan et al, 1995; Junge et al, 1996; Vik and Antonio, 1994), and the c-ring in turn drives the rotation of the attached central stalk, which sequentially actuates the conformational change of the three catalytic units for synthesizing ATP (Boyer, 1997)
Summary
The ATP synthase ( known as the F1Fo-ATPase), being recognized as the principle energy transformer in living organisms, is a membrane-integrated multi-subunit protein complex (von Ballmoos et al, 2009). We propose an alternative rotary model for the ATP synthase such that what rotates is the catalytic 3 3 cylinder rather than the central stalk and the membrane-embedded c-ring.
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