F1-ATPase is an ATP-driven rotary motor in which a rod-shaped γ subunit rotates inside a cylinder made of α3β 3 subunits. To elucidate the conformations of rotating F 1, we measured fluorescence resonance energy transfer (FRET) between a donor on one of the three βs and an acceptor on γ in single F 1 molecules. The yield of FRET changed stepwise at low ATP concentrations, reflecting the stepwise rotation of γ. In the ATP-waiting state, the FRET yields indicated a γ position ≈40° counterclockwise (= direction of rotation) from that in the crystal structures of mitochondrial F1, suggesting that the crystal structures mimic a metastable state before product release.
|Proceedings of the National Academy of Sciences of the United States of America
|Published - 2003 8月 5
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