F1, a water-soluble portion of F0F1-ATP synthase, is an ATP hydrolysis-driven rotary motor. The central γ-subunit rotates in the α3β3 cylinder by repeating the following four stages of rotation: ATP-binding dwell, rapid 80° substep rotation, interim dwell, and rapid 40° substep rotation. At least two 1-ms catalytic events occur in the interim dwell, but it is still unclear which steps in the ATPase cycle, except for ATP binding, correspond to these events. To discover which steps, we analyzed rotations of F1 subcomplex (α3β3γ) from thermophilic Bacillus PS3 under conditions where cleavage of ATP at the catalytic site is decelerated: hydrolysis of ATP by the catalytic-site mutant F1 and hydrolysis of a slowly hydrolyzable substrate ATPγS (adenosine 5′-[γ -thio]triphosphate) by wild-type F1. In both cases, interim dwells were extended as expected from bulk phase kinetics, confirming that cleavage of ATP takes place during the interim dwell. Furthermore, the results of ATPγS hydrolysis by the mutant F1 ensure that cleavage of ATP most likely corresponds to one of the two 1-ms events and not some other faster undetected event. Thus, cleavage of ATP on F1 occurs in 1 ms during the interim dwell, and we call this interim dwell catalytic dwell.
|ジャーナル||Proceedings of the National Academy of Sciences of the United States of America|
|出版ステータス||Published - 2003 12 9|
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