How do molecular motors convert chemical energy to mechanical work? Helicases and nucleic acids offer simple motor systems for extensive biochemical and biophysical analyses. Atomic resolution structures of UvrD-like helicases complexed with DNA in the presence of AMPPNP, ADP.Pi, and Pi reveal several salient points that aid our understanding of mechanochemical coupling. Each ATPase cycle causes two motor domains to rotationally close and open. At a minimum, two motor-track contact points of alternating tight and loose attachment convert domain rotations to unidirectional movement. A motor is poised for action only when fully in contact with its track and, if applicable, working against a load. The orientation of domain rotation relative to the track determines whether the movement is linear, spiral, or circular. Motors powered by ATPases likely deliver each power stroke in two parts, before and after ATP hydrolysis. Implications of these findings for analyzing hexameric helicase, F(1)F(0) ATPase, and kinesin are discussed.

中文翻译：

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从 UvrD 解旋酶中吸取的教训：定向运动的机制。

分子马达如何将化学能转化为机械功？解旋酶和核酸为广泛的生化和生物物理分析提供了简单的运动系统。在 AMPPNP、ADP.Pi 和 Pi 存在下与 DNA 复合的 UvrD 样解旋酶的原子分辨率结构揭示了几个有助于我们理解机械化学耦合的要点。每个 ATPase 循环都会导致两个运动域旋转关闭和打开。至少，交替紧密和松散连接的两个电机轨道接触点将域旋转转换为单向运动。电机只有在完全与其轨道接触并且在适用的情况下对抗负载时才准备好动作。域旋转相对于轨道的方向决定了移动是线性的、螺旋的还是圆形的。由 ATP 酶驱动的电机可能会在 ATP 水解之前和之后分两部分提供每个动力冲程。讨论了这些发现对分析六聚解旋酶、F(1)F(0) ATPase 和驱动蛋白的影响。