title: Simple mechanism whereby the F1-ATPase motor rotates with near-perfect chemomechanical energy conversion.
abstract: F1-ATPase is a motor enzyme in which a central shaft γ subunit rotates 120° per ATP in the cylinder made of α3β3 subunits. During rotation, the chemical energy of ATP hydrolysis (ΔGATP) is converted almost entirely into mechanical work by an elusive mechanism. We measured the force for rotation (torque) under various ΔGATP conditions as a function of rotation angles of the γ subunit with quasi-static, single-molecule manipulation and estimated mechanical work (torque × traveled angle) from the area of the function. The torque functions show three sawtooth-like repeats of a steep jump and linear descent in one catalytic turnover, indicating a simple physical model in which the motor is driven by three springs aligned along a 120° rotation angle. Although the second spring is unaffected by ΔGATP, activation of the first spring (timing of the torque jump) delays at low [ATP] (or high [ADP]) and activation of the third spring delays at high [Pi]. These shifts decrease the size and area of the sawtooth (magnitude of the work). Thus, F1-ATPase responds to the change of ΔGATP by shifting the torque jump timing and uses ΔGATP for the mechanical work with near-perfect efficiency.
authors.affiliation: Department of Molecular Bioscience, Kyoto Sangyo University, Kamigamo Motoyama, Kyoto 603-8555, Japan; International Cooperative Research Project, ATP Synthesis Regulation Project, Japan Science and Technology Agency, Aomi 2-3-6, Tokyo 135-0064, Japan;
authors.forename: Ei-ichiro
authors.initials: E
authors.lastname: Saita
authors.affiliation: Department of Molecular Bioscience, Kyoto Sangyo University, Kamigamo Motoyama, Kyoto 603-8555, Japan; International Cooperative Research Project, ATP Synthesis Regulation Project, Japan Science and Technology Agency, Aomi 2-3-6, Tokyo 135-0064, Japan; Department of Physics, Faculty of Science and Engineering, Waseda University, Shinjuku-ku, Tokyo 169-8555, Japan.
authors.forename: Toshiharu
authors.initials: T
authors.lastname: Suzuki
authors.affiliation: Department of Physics, Faculty of Science and Engineering, Waseda University, Shinjuku-ku, Tokyo 169-8555, Japan.
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Kinosita
authors.affiliation: Department of Molecular Bioscience, Kyoto Sangyo University, Kamigamo Motoyama, Kyoto 603-8555, Japan; International Cooperative Research Project, ATP Synthesis Regulation Project, Japan Science and Technology Agency, Aomi 2-3-6, Tokyo 135-0064, Japan; masasuke.yoshida@cc.kyoto-su.ac.jp.
authors.forename: Masasuke
authors.initials: M
authors.lastname: Yoshida
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D001407:Bacillus / Q000378:metabolism; D006868:Hydrolysis; D060328:Magnetic Phenomena; D008954:Models, Biological; D020409:Molecular Motor Proteins / Q000737:chemistry / Q000378:metabolism*; D006180:Proton-Translocating ATPases / Q000737:chemistry / Q000378:metabolism*; D012399:Rotation; D013816:Thermodynamics; D019415:Torque
chemical_list: D020409:Molecular Motor Proteins; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D006180:Proton-Translocating ATPases
keywords: ATP synthase; F1-ATPase; rotary motor; single molecule; torque