Mechanism of microtubule lumen entry for the α-tubulin acetyltransferase enzyme αTAT1
Mechanism of microtubule lumen entry for the α-tubulin acetyltransferase enzyme αTAT1
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DOI：
10.1073/pnas.1605397113
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发表时间：
2016-11-15
影响因子：
11.1
通讯作者：
Gardner, Melissa K.
中科院分区：
文献类型：
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作者：
Coombes, Courtney;Yamamoto, Ami;Gardner, Melissa K.
微管是细胞内的结构聚合物，可进行翻译后修饰。这些翻译后修饰在细胞中产生功能上不同的微管网络子集，乙酰化是微管中空腔中发生的唯一修饰。虽然已知α-微管蛋白乙酰转移酶（α TAT 1）是负责微管乙酰化的主要酶，但α TAT 1如何进入微管腔以接近其乙酰化位点的机制还不清楚。通过进行生物化学测定、荧光和电子显微镜实验以及计算机模拟，我们发现α TAT 1通过微管末端以及晶格中的弯曲或断裂进入微管腔。因此，微管结构是乙酰化过程中的重要决定因素。此外，一旦α-TAT 1进入微管腔，由于α-TAT 1快速重新结合到高度浓缩的α-微管蛋白乙酰化位点上，因此α-TAT 1在腔内的移动性由α-TAT 1对其乙酰化位点的亲和力控制。这些结果对于乙酰化如何在细胞内稳定的微管亚群上逐渐积累具有重要意义。
Microtubules are structural polymers inside of cells that are subject to posttranslational modifications. These posttranslational modifications create functionally distinct subsets of microtubule networks in the cell, and acetylation is the only modification that takes place in the hollow lumen of the microtubule. Although it is known that the a-tubulin acetyltransferase (alpha TAT1) is the primary enzyme responsible for microtubule acetylation, the mechanism for how alpha TAT1 enters the microtubule lumen to access its acetylation sites is not well understood. By performing biochemical assays, fluorescence and electron microscopy experiments, and computational simulations, we found that alpha TAT1 enters the microtubule lumen through the microtubule ends, and through bends or breaks in the lattice. Thus, microtubule structure is an important determinant in the acetylation process. In addition, once alpha TAT1 enters the microtubule lumen, the mobility of alpha TAT1 within the lumen is controlled by the affinity of alpha TAT1 for its acetylation sites, due to the rapid rebinding of alpha TAT1 onto highly concentrated a-tubulin acetylation sites. These results have important implications for how acetylation could gradually accumulate on stable subsets of microtubules inside of the cell.