Institute of Protein Research, School of Life Sciences and Technology, Tongji University, Shanghai, China.
FEBS J. 2013 Aug;280(16):3868-77. doi: 10.1111/febs.12385. Epub 2013 Jul 12.
Spastin is an AAA (ATPase associated with diverse cellular activities) protein with microtubule (MT)-severing activity. The spastin-encoding gene was identified as the most often mutated gene in the human neurodegenerative disease hereditary spastic paraplegia. Although the structure of the AAA domain of spastin has been determined, the mechanism by which spastin severs MTs remains elusive. Here, we studied the MT-binding and nucleotide-binding properties of spastin, as well as their interplay. The results suggest that ATP-bound spastin interacts strongly and cooperatively with MTs; this interaction stimulates ATP hydrolysis by spastin. After ATP hydrolysis, spastin dissociates from MTs, and then exchanges ADP for ATP in solution for the next round of work. In particular, spastin in the ternary complex of MT-spastin-ATP is the most cooperative state during the working cycle, and is probably the force-generating state that is responsible for MT severing. The results presented in this study establish the nucleotide cycle of spastin in correlation with its MT-binding properties, and provide a biochemical framework for further studies of the working mechanism of spastin.
痉挛蛋白是一种具有微管（MT）切割活性的 AAA（与多种细胞活动相关的 ATP 酶）蛋白。痉挛蛋白编码基因被鉴定为人类神经退行性疾病遗传性痉挛性截瘫中最常突变的基因。尽管痉挛蛋白的 AAA 结构域的结构已经确定，但痉挛蛋白切割 MT 的机制仍然难以捉摸。在这里，我们研究了痉挛蛋白的 MT 结合和核苷酸结合特性，以及它们的相互作用。结果表明，ATP 结合的痉挛蛋白与 MT 强烈且协同地相互作用；这种相互作用刺激了痉挛蛋白的 ATP 水解。在 ATP 水解后，痉挛蛋白从 MT 上解离，然后在溶液中交换 ADP 为 ATP，以进行下一轮工作。特别是，在 MT-痉挛蛋白-ATP 的三元复合物中，痉挛蛋白处于工作循环中最具协作性的状态，可能是负责 MT 切割的力产生状态。本研究中呈现的结果将痉挛蛋白的核苷酸循环与其 MT 结合特性相关联，并为进一步研究痉挛蛋白的工作机制提供了生化框架。
