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Effect of external torque on the ATP-driven rotation of F1-ATPase |
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| Authors: | Watanabe-Nakayama Takahiro Toyabe Shoichi Kudo Seishi Sugiyama Shigeru Yoshida Masasuke Muneyuki Eiro |
| Institution: | a Chemical Resources Laboratory, Tokyo Institute of Technology, Yokohama 226-8503, Japan b Department of Physics, Faculty of Science and Engineering, Chuo University, Kasuga 1-13-27, Bunkyo-ku, Tokyo 112-8551, Japan c Faculty of Engineering, Toin University of Yokohama, Yokohama 225-8502, Japan d National Food Research Institute, Instrumentation Engineering Laboratory, Tsukuba 305-8642, Japan |
| Abstract: | F1-ATPase is a rotary molecular motor powered by the torque generated by another rotary motor F0 to synthesize ATP in vivo. Therefore elucidation of the behavior of F1 under external torque is very important. Here, we applied controlled external torque by electrorotation and investigated the ATP-driven rotation for the first time. The rotation was accelerated by assisting torque and decelerated by hindering torque, but F1 rarely showed rotations in the ATP synthesis direction. This is consistent with the prediction by models based on the assumption that the rotation is tightly coupled to ATP hydrolysis and synthesis. At low ATP concentrations (2 and 5 μM), 120° stepwise rotation was observed. Due to the temperature rise during experiment, quantitative interpretation of the data is difficult, but we found that the apparent rate constant of ATP binding clearly decreased by hindering torque and increased by assisting torque. |
| Keywords: | Molecular motor Single molecule F1-ATPase External force Tight coupling |
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