Uemura Sotaro, Ishiwata Shin'ichi
Department of Physics, School of Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan.
Nat Struct Biol. 2003 Apr;10(4):308-11. doi: 10.1038/nsb911.
Kinesin is an ATP-driven molecular motor that moves processively along a microtubule. Processivity has been explained as a mechanism that involves alternating single- and double-headed binding of kinesin to microtubules coupled to the ATPase cycle of the motor. The internal load imposed between the two bound heads has been proposed to be a key factor regulating the ATPase cycle in each head. Here we show that external load imposed along the direction of motility on a single kinesin molecule enhances the binding affinity of ADP for kinesin, whereas an external load imposed against the direction of motility decreases it. This coupling between loading direction and enzymatic activity is in accord with the idea that the internal load plays a key role in the unidirectional and cooperative movement of processive motors.
驱动蛋白是一种由ATP驱动的分子马达，它能沿微管持续移动。持续性被解释为一种机制，该机制涉及驱动蛋白与微管的单头和双头交替结合，并与马达的ATP酶循环相耦合。两个结合头部之间施加的内部负载被认为是调节每个头部ATP酶循环的关键因素。在这里，我们表明，沿单个驱动蛋白分子的运动方向施加的外部负载会增强ADP与驱动蛋白的结合亲和力，而与运动方向相反施加的外部负载则会降低这种亲和力。负载方向与酶活性之间的这种耦合与内部负载在持续性马达的单向协同运动中起关键作用的观点一致。
