期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2016
卷号：113
期号：46
页码：E7176-E7184
DOI：10.1073/pnas.1605397113
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceTAT1 is an enzyme that acetylates microtubules inside of cells, and acetylation is an important posttranslational microtubule modification. However, microtubules are long tubes, and the acetylation site for TAT1 is on the inside of this tube. We investigated how TAT1 enters the microtubule and moves around to access its acetylation sites once inside. We found that TAT1 enters microtubules through its ends but does not move efficiently inside of the microtubule. However, a lowered affinity allows the enzyme to move more efficiently and leads to longer stretches of acetylation. Therefore, acetylation of microtubules could be controlled in the cell by modulating the affinity of TAT1 for its acetylation site or increasing the number of microtubule ends. 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 -tubulin acetyltransferase (TAT1) is the primary enzyme responsible for microtubule acetylation, the mechanism for how 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 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 TAT1 enters the microtubule lumen, the mobility of TAT1 within the lumen is controlled by the affinity of TAT1 for its acetylation sites, due to the rapid rebinding of TAT1 onto highly concentrated -tubulin acetylation sites. These results have important implications for how acetylation could gradually accumulate on stable subsets of microtubules inside of the cell.
