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Asymmetry in the F1-ATPase and its implications for the rotational cycle.

ABSTRACT: ATP synthase uses a rotary mechanism to carry out its cellular function of manufacturing ATP. The central gamma-shaft rotates inside a hexameric cylinder composed of alternating alpha- and beta-subunits. When operating in the hydrolysis direction under high frictional loads and low ATP concentrations, a coordinated mechanochemical cycle in the three catalytic sites of the beta-subunits rotates the gamma-shaft in three 120 degrees steps. At low frictional loads, the 120 degrees steps alternate with three ATP-independent substeps separated by approximately 30 degrees. We present a quantitative model that accounts for these substeps and show that the observed pauses are due to 1), the asymmetry of the F(1) hexamer that produces a propeller-like motion of the power-stroke and 2), the relatively tight binding of ADP to the catalytic sites.

SUBMITTER: Sun SX

PROVIDER: S-EPMC1303975 | biostudies-literature | 2004 Mar

REPOSITORIES: biostudies-literature

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Asymmetry in the F1-ATPase and its implications for the rotational cycle.

Sun Sean X SX Wang Hongyun H Oster George G

Biophysical journal 20040301 3

ATP synthase uses a rotary mechanism to carry out its cellular function of manufacturing ATP. The central gamma-shaft rotates inside a hexameric cylinder composed of alternating alpha- and beta-subunits. When operating in the hydrolysis direction under high frictional loads and low ATP concentrations, a coordinated mechanochemical cycle in the three catalytic sites of the beta-subunits rotates the gamma-shaft in three 120 degrees steps. At low frictional loads, the 120 degrees steps alternate wi ...[more]

PMID: 14990467

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