Effect of external torque on the ATP-driven rotation of F1-ATPase.
F(1)-ATPase is a rotary molecular motor powered by the torque generated by another rotary motor F(0) to synthesize ATP in vivo. Therefore elucidation of the behavior of F(1) 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 F(1) 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 microM), 120 degrees 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.
Watanabe-Nakayama
Takahiro
T
Chemical Resources Laboratory, Tokyo Institute of Technology, Yokohama 226-8503, Japan.
Toyabe
Shoichi
S
Kudo
Seishi
S
Sugiyama
Shigeru
S
Yoshida
Masasuke
M
Muneyuki
Eiro
E
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D001407:Bacillus / Q000201:enzymology*; D020409:Molecular Motor Proteins / Q000378:metabolism; D006180:Proton-Translocating ATPases / Q000378:metabolism*; D012399:Rotation; D013696:Temperature; D013997:Time Factors; D019415:Torque
D020409:Molecular Motor Proteins; D000255:Adenosine Triphosphate; D006180:Proton-Translocating ATPases