1: Philos Trans R Soc Lond B Biol Sci  2000 Apr 29;355(1396):473-89 

A rotary molecular motor that can work at near 100% efficiency.

Kinosita K Jr, Yasuda R, Noji H, Adachi K.

Department of Physics, Faculty of Science and Technology, Keio University,
Yokohama, Japan.

A single molecule of F1-ATPase is by itself a rotary motor in which a central
gamma-subunit rotates against a surrounding cylinder made of
alpha3beta3-subunits. Driven by the three betas that sequentially hydrolyse ATP,
the motor rotates in discrete 120 degree steps, as demonstrated in video images
of the movement of an actin filament bound, as a marker, to the central
gamma-subunit. Over a broad range of load (hydrodynamic friction against the
rotating actin filament) and speed, the F1 motor produces a constant torque of
ca. 40 pN nm. The work done in a 120 degree step, or the work per ATP molecule,
is thus ca. 80 pN nm. In cells, the free energy of ATP hydrolysis is ca. 90 pN
nm per ATP molecule, suggesting that the F1 motor can work at near 100%
efficiency. We confirmed in vitro that F1 indeed does ca. 80 pN nm of work under
the condition where the free energy per ATP is 90 pN nm. The high efficiency may
be related to the fully reversible nature of the F1 motor: the ATP synthase, of
which F1 is a part, is considered to synthesize ATP from ADP and phosphate by
reverse rotation of the F1 motor. Possible mechanisms of F1 rotation are
discussed.

Publication Types:
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PMID: 10836501 [PubMed - indexed for MEDLINE]