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Chemo-Mechanical Coupling in F1-ATPase Revealed by Catalytic Site Occupancy during Catalysis |
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| Authors: | Rieko Shimo-Kon Hiroshi Sakai Masasuke Yoshida |
| Affiliation: | † Department of Physics, Faculty of Science and Engineering, Waseda University, Okubo, Shinjuku-ku, Tokyo, Japan ‡ Department of Physics, Faculty of Science and Engineering, Chuo University, Kasuga, Bunkyo-ku, Tokyo, Japan § Department of Food and Nutritional Sciences, Graduate School of Nutritional and Environmental Sciences, University of Shizuoka, Yada, Shizuoka, Japan ¶ Bio-Resources Division, Chemical Resources Laboratory, Tokyo Institute of Technology, Nagatsuta, Midori-ku, Yokohama, Japan |
| Abstract: | F1-ATPase is a rotary molecular motor in which the central γ subunit rotates inside a cylinder made of α3β3 subunits. To clarify how ATP hydrolysis in three catalytic sites cooperate to drive rotation, we measured the site occupancy, the number of catalytic sites occupied by a nucleotide, while assessing the hydrolysis activity under identical conditions. The results show hitherto unsettled timings of ADP and phosphate releases: starting with ATP binding to a catalytic site at an ATP-waiting γ angle defined as 0°, phosphate is released at ∼200°, and ADP is released during quick rotation between 240° and 320° that is initiated by binding of a third ATP. The site occupancy remains two except for a brief moment after the ATP binding, but the third vacant site can bind a medium nucleotide weakly. |
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