Gulick A M, Song H, Endow S A, Rayment I
Department of Biochemistry, University of Wisconsin, Madison 53705, USA.
Biochemistry. 1998 Feb 17;37(7):1769-76. doi: 10.1021/bi972504o.
The kinesin family of motor proteins, which contain a conserved motor domain of approximately 350 amino acids, generate movement against microtubules. Over 90 members of this family have been identified, including motors that move toward the minus or plus end of microtubules. The Kar3 protein from Saccharomyces cerevisiae is a minus end-directed kinesin family member that is involved in both nuclear fusion, or karyogamy, and mitosis. The Kar3 protein is 729 residues in length with the motor domain located in the C-terminal 347 residues. Recently, the three-dimensional structures of two kinesin family members have been reported. These structures include the motor domains of the plus end-directed kinesin heavy chain [Kull, F. J., et al. (1996) Nature 380, 550-555] and the minus end-directed Ncd [Sablin, E. P., et al. (1996) Nature 380, 555-559]. We now report the structure of the Kar3 protein complexed with Mg.ADP obtained from crystallographic data to 2.3 A. The structure is similar to those of the earlier kinesin family members, but shows differences as well, most notably in the length of helix alpha 4, a helix which is believed to be involved in conformational changes during the hydrolysis cycle.
驱动蛋白家族的运动蛋白含有一个约350个氨基酸的保守运动结构域，能逆着微管产生运动。该家族已鉴定出90多个成员，包括向微管负端或正端移动的驱动蛋白。酿酒酵母中的Kar3蛋白是一种向负端移动的驱动蛋白家族成员，参与细胞核融合（即核配）和有丝分裂。Kar3蛋白长度为729个残基，其运动结构域位于C端的347个残基中。最近，已报道了两种驱动蛋白家族成员的三维结构。这些结构包括向正端移动的驱动蛋白重链的运动结构域[库尔，F. J.等人（1996年）《自然》380卷，550 - 555页]和向负端移动的Ncd[萨布林，E. P.等人（1996年）《自然》380卷，555 - 559页]。我们现在报道从晶体学数据得到的与Mg·ADP复合的Kar3蛋白的结构，分辨率为2.3埃。该结构与早期驱动蛋白家族成员的结构相似，但也有差异，最显著的是α4螺旋的长度不同，据信该螺旋参与水解循环中的构象变化。
