XMAP215 is a processive microtubule polymerase
XMAP215 is a processive microtubule polymerase
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DOI：
10.1016/j.cell.2007.11.043
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发表时间：
2008-01-11
期刊：
影响因子：
64.5
通讯作者：
Hyman, Anthony A.
中科院分区：
文献类型：
--
作者：
Brouhard, Gary J.;Stear, Jeffrey H.;Hyman, Anthony A.
在细胞增殖和分化过程中，微管的快速生长对微管骨架的快速组装至关重要。XMAP215属于促进微管生长的保守蛋白家族。为了确定XMAP215如何加速生长，我们开发了一种单分子实验，直接观察XMAP215- gfp与动态微管的相互作用。XMAP215结合自由微管蛋白，形成1:1复合物，与微管晶格相互作用，并通过扩散促进机制靶向末端。XMAP215以“尖端跟踪”的形式持续存在于多轮微管蛋白亚基添加的正端。“这些结果表明，XMAP215是一种过程聚合酶，可直接催化多达25个微管蛋白二聚体添加到生长的正端。在某些情况下，XMAP215还可以催化逆反应，即微管收缩。XMAP215与肌动蛋白聚合酶formins之间的相似性表明，过程尖端跟踪是刺激细胞骨架聚合物生长的常见机制。
Fast growth of microtubules is essential for rapid assembly of the microtubule cytoskeleton during cell proliferation and differentiation. XMAP215 belongs to a conserved family of proteins that promote microtubule growth. To determine how XMAP215 accelerates growth, we developed a single-molecule assay to visualize directly XMAP215-GFP interacting with dynamic microtubules. XMAP215 binds free tubulin in a 1: 1 complex that interacts with the microtubule lattice and targets the ends by a diffusion-facilitated mechanism. XMAP215 persists at the plus end for many rounds of tubulin subunit addition in a form of "tip tracking.'' These results show that XMAP215 is a processive polymerase that directly catalyzes the addition of up to 25 tubulin dimers to the growing plus end. Under some circumstances XMAP215 can also catalyze the reverse reaction, namely microtubule shrinkage. The similarities between XMAP215 and formins, actin polymerases, suggest that processive tip tracking is a common mechanism for stimulating the growth of cytoskeletal polymers.