Direction determination in the minus-end-directed kinesin motor ncd
Direction determination in the minus-end-directed kinesin motor ncd
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DOI：
10.1038/27463
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发表时间：
1998-10-22
期刊：
影响因子：
64.8
通讯作者：
Fletterick, RJ
中科院分区：
文献类型：
--
作者：
Sablin, EP;Case, RB;Fletterick, RJ
运动蛋白超家族的马达蛋白沿着微管运输细胞内的货物。尽管不同的Kinesin蛋白在其运动催化核心中有30%-50%的氨基酸相同，但一些移动到微管的正端，而另一些则移动到相反的方向(1，2)。传统的Kinesin(参与细胞器运输的正端定向马达)和NCD(参与染色体分离的负端定向马达)的催化核心的晶体结构几乎相同(3，4)；因此，它们相反运动方向的结构基础尚不清楚。在这里，我们证明了NCD‘Neck’，由超家族保守的催化核心旁边的13个类特异性残基组成，对于负端定向运动是必不可少的，因为这些颈部残基的突变改变了NCD的运动方向。通过求解功能性NCD二聚体的2.5埃结构，我们发现NCD颈部(盘绕线圈)不同于NCD颈部(5，6)中相应的运动区域，尽管这两个颈部都与催化核心中类似的元件相互作用。不同的颈部结构还赋予NCD和Kinesin二聚体不同的对称性，并以适当的方向偏置将这些马达定位在微管上。
Motor proteins of the kinesin superfamily transport intracellular cargo along microtubules. Although different kinesin proteins share 30-50% amino-acid identity in their motor catalytic cores, some move to the plus end of microtubules whereas others travel in the opposite direction(1,2). Crystal structures of the Catalytic cores of conventional kinesin (a plus-end-directed motor involved in organelle transport) and ncd (a minus-end-directed motor involved in chromosome segregation) are nearly identical(3,4); therefore, the structural basis for their opposite directions of movement is unknown. Here we show that the ncd 'neck', made up of 13 class-specific residues next to the superfamily-conserved catalytic core, is essential for minus-end-directed motility, as mutagenesis of these neck residues reverses the direction of ncd motion. By solving the 2.5 Angstrom structure of a functional ncd dimer,we show that the ncd neck(a coiled-coil) differs from the corresponding region in the kinesin neck tan interrupted beta-strand)(5,6), although both necks interact with similar elements in the catalytic cores. The distinct neck architectures also confer different symmetries to the ncd and kinesin dimers and position these motors with appropriate directional bias on the microtubule.