The C-terminal region of the motor protein MCAK controls its structure and activity through a conformational switch.
The C-terminal region of the motor protein MCAK controls its structure and activity through a conformational switch.
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DOI：
10.7554/elife.06421
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发表时间：
2015-04-27
期刊：
影响因子：
7.7
通讯作者：
Welburn JP
中科院分区：
文献类型：
--
作者：
Talapatra SK;Harker B;Welburn JP
在细胞分裂过程中，微管动力学的精确调控是至关重要的。Kinesin-13运动蛋白MCAK是一种有效的微管解聚酶。ATPase结构域两侧不同的非运动区在调节其靶向性和活性方面起着关键作用。然而，在全长MCAK的背景下，非运动区功能的分子基础尚不清楚。在这里，我们确定了MCAK运动域与其调控的C末端结合的结构。我们的分析表明，MCAK的C-末端在溶液中与两个运动域结合，并在微管结合时变构移位，这使得它能够在微管末端强劲积累。这些结果表明，MCAK在可溶性到微管结合的转变过程中经历了涉及其C末端的远程构象变化，并且C末端与马达的相互作用是MCAK催化循环中的结构中间产物。总之，我们的工作揭示了驱动蛋白-13活性调节的内在分子机制。DOI：http://dx.doi.org/10.7554/eLife.06421.001在细胞内，有一种被称为细胞骨架的支架状结构，它提供形状和结构支持，并作为分子在细胞周围移动的运输网络。这种支架包含称为微管的高度动态聚合物，这种聚合物由一种名为微管蛋白的蛋白质制成。微管末端的不断生长和收缩对于根据细胞的需要重建和适应细胞骨架是必不可少的。一种名为MCAK的蛋白质属于一种可以沿着微管移动的马达蛋白质家族。它通常结合到微管的末端以缩短它们。以前的研究发现，一个MCAK蛋白与另一个MCAK蛋白结合，形成一个更大的分子，称为二聚体。MCAK蛋白的一部分形成了一个所谓的运动域，使该蛋白能够结合到微管上。蛋白质的一端，被称为C-末端，控制着这个运动域的活动。然而，目前还不清楚这是如何运作的。Talapatra等人。现在已经用一种叫做X射线结晶学的技术揭示了MCAK的运动域的三维结构和C-末端。实验表明，C末端与运动结构域结合，促进了二聚体的形成。C末端的一小段氨基酸--蛋白质的组成成分--与两个马达分子相互作用。这个“基序”也存在于各种动物的其他类似蛋白质中。然而，一旦MCAK与微管结合，微管就会触发C末端从运动域中释放。这使得MCAK能够更强地与微管结合。实验还表明，C末端与运动域的结合改变了MCAK与微管的结合能力，从而鼓励蛋白质到达聚合物的末端。还需要进一步的工作来观察其他马达蛋白是否以类似的方式发挥作用。DOI：http://dx.doi.org/10.7554/eLife.06421.002
The precise regulation of microtubule dynamics is essential during cell division. The kinesin-13 motor protein MCAK is a potent microtubule depolymerase. The divergent non-motor regions flanking the ATPase domain are critical in regulating its targeting and activity. However, the molecular basis for the function of the non-motor regions within the context of full-length MCAK is unknown. Here, we determine the structure of MCAK motor domain bound to its regulatory C-terminus. Our analysis reveals that the MCAK C-terminus binds to two motor domains in solution and is displaced allosterically upon microtubule binding, which allows its robust accumulation at microtubule ends. These results demonstrate that MCAK undergoes long-range conformational changes involving its C-terminus during the soluble to microtubule-bound transition and that the C-terminus-motor interaction represents a structural intermediate in the MCAK catalytic cycle. Together, our work reveals intrinsic molecular mechanisms underlying the regulation of kinesin-13 activity. DOI: http://dx.doi.org/10.7554/eLife.06421.001 Within a cell, there is a scaffold-like structure called the cytoskeleton that provides shape and structural support, and acts as a transport network for the movement of molecules around the cell. This scaffold contains highly dynamic polymers called microtubules that are made from a protein called tubulin. The constant growth and shrinking of the ends of the microtubules is essential to rebuild and adapt the cytoskeleton according to the needs of the cell. A protein called MCAK belongs to a family of motor proteins that can move along microtubules. It generally binds to the ends of the microtubules to shorten them. Previous studies have found that a single MCAK protein binds to another MCAK protein to form a larger molecule known as a dimer. Part of the MCAK protein forms a so-called motor domain, which enables this protein to bind to the microtubules. One end of the protein, known as the C-terminus, controls the activity of this motor domain. However, it is not clear how this works. Talapatra et al. have now revealed the three-dimensional structure of MCAK's motor domain with the C-terminus using a technique called X-ray crystallography. The experiments show that the C-terminus binds to the motor domain, which promotes the formation of the dimers. A short stretch of amino acids—the building blocks of proteins—in the C-terminus interacts with two motor molecules. This ‘motif’ is also found in other similar proteins from a variety of animals. However, once MCAK binds to a microtubule, the microtubule triggers the release of the C-terminus from the motor domain. This allows MCAK to bind more strongly to the microtubule. The experiments also show that the binding of the C-terminus to the motor domain alters the ability of MCAK to associate with microtubules, which encourages the protein to reach the ends of the polymers. Future work is required to see whether other motor proteins work in a similar way. DOI: http://dx.doi.org/10.7554/eLife.06421.002