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SYLS: Life Sciences on the Nanometer Scale - Physics Meets Biology

SYLS 5: Symposium "Life Sciences on the Nanometer Scale - Physics Meets Biology"

SYLS 5.1: Hauptvortrag

Donnerstag, 11. März 2004, 11:15–11:45, H 37

Mechano-Chemical Coupling in F₁-ATPase — •Kazuhiko Kinosita — Center for Integrative Bioscience, Okazaki National Research Institutes

The protein F₁-ATPase is a rotary motor made of a single molecule. Its central γ subunit rotates against a surrounding cylinder made of α₃β₃ subunits. This rotary motor is powered by sequential ATP hydrolysis in the three β subunits, and reverse rotation of the motor is expected to drive ATP synthesis. We have shown, by single-molecule imaging, that (i) the rotary torque is nearly independent of the rotation angle, (ii) 80-90 pN nm of mechanical work can be done per ATP hydrolyzed, (iii) binding of ATP causes ∼90^o rotation, and (iv) release of the last hydrolysis product causes further ∼30^o rotation. Point ii implies that the efficiency of chemo-mechanical conversion may reach ∼100 %. Points i-iv allowed us to infer the angle-dependent potential energies for γ rotation for each of chemical intermediates that appear during rotation. Details of the coupling scheme between chemical reactions on the three catalytic sites and mechanical rotation of the rotor are beginning to unravel.