Biophysics Graduate Group, University of California, Berkeley, Berkeley, California, USA.
Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, California, USA.
Nat Struct Mol Biol. 2015 Jan;22(1):73-80. doi: 10.1038/nsmb.2930. Epub 2014 Dec 8.
Cytoplasmic dynein is an AAA+ motor responsible for intracellular cargo transport and force generation along microtubules (MTs). Unlike kinesin and myosin, dynein contains multiple ATPase subunits, with AAA1 serving as the primary catalytic site. ATPase activity at AAA3 is also essential for robust motility, but its role in dynein's mechanochemical cycle remains unclear. Here, we introduced transient pauses in Saccharomyces cerevisiae dynein motility by using a slowly hydrolyzing ATP analog. Analysis of pausing behavior revealed that AAA3 hydrolyzes nucleotide an order of magnitude more slowly than AAA1, and the two sites do not coordinate. ATPase mutations to AAA3 abolish the ability of dynein to modulate MT release. Nucleotide hydrolysis at AAA3 lifts this 'MT gate' to allow fast motility. These results suggest that AAA3 acts as a switch that repurposes cytoplasmic dynein for fast cargo transport and MT-anchoring tasks in cells.
细胞质动力蛋白是一种 AAA+ 马达，负责沿微管（MTs）进行细胞内货物运输和力的产生。与驱动蛋白和肌球蛋白不同，动力蛋白包含多个 ATP 酶亚基，AAA1 作为主要的催化位点。AAA3 的 ATP 酶活性对于强大的运动性也是必不可少的，但它在动力蛋白的机械化学循环中的作用仍不清楚。在这里，我们通过使用缓慢水解的 ATP 类似物在酿酒酵母动力蛋白的运动中引入短暂的暂停。对暂停行为的分析表明，AAA3 比 AAA1 水解核苷酸的速度慢一个数量级，并且两个位点不协调。ATP 酶突变到 AAA3 会使动力蛋白失去调节 MT 释放的能力。AAA3 上的核苷酸水解会抬起这个“MT 门”，从而允许快速运动。这些结果表明，AAA3 充当了一个开关，将细胞质动力蛋白重新用于细胞中快速的货物运输和 MT 锚定任务。
