Trapping the ATP binding state leads to a detailed understanding of the F-1-ATPase mechanism

• The rotary motor enzyme FoF1-ATP synthase uses the protonmotive force across a membrane to synthesize ATP from ADP and P-i (H2PO4-) under cellular conditions that favor the hydrolysis reaction by a factor of 2 x 10(5). This remarkable ability to drive a reaction away from equilibrium by harnessing an external force differentiates it from an ordinary enzyme, which increases the rate of reaction without shifting the equilibrium. Hydrolysis takes place in the neighborhood of one conformation of the catalytic moiety F-1-ATPase, whose structure is known from crystallography. By use of molecular dynamics simulations we trap a second structure, which is rotated by 40 degrees from the catalytic dwell conformation and represents the state associated with ATP binding, in accord with single-molecule experiments. Using the two structures, we show why Pi is not released immediately after ATP hydrolysis, but only after a subsequent 120 degrees rotation, in agreement with experiment. A concerted conformational change of the alpha(3)beta(3) crown is shown to induce the 40 degrees rotation of the gamma-subunit only when the beta(E) subunit is empty, whereas with Pi bound, beta(E) serves as a latch to prevent the rotation of gamma. The present results provide a rationalization of how F-1-ATPase achieves the coupling between the small changes in the active site of beta(DP) and the 40 degrees rotation of gamma.

Ämnesord

NATURVETENSKAP  -- Kemi -- Annan kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Other Chemistry Topics (hsv//eng)

Nyckelord

F-1-ATPase

chemomechanical coupling

ATP waiting state

molecular dynamics

P-i release

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