Talapatra S K, Schüttelkopf A W, Kozielski F
Molecular Motor Laboratory, The Beatson Institute for Cancer Research, Garscube Estate, Switchback Road, Bearsden, Glasgow G61 1BD, Scotland, UK.
Acta Crystallogr D Biol Crystallogr. 2012 Oct;68(Pt 10):1311-9. doi: 10.1107/S0907444912027965. Epub 2012 Sep 13.
The human kinesin Eg5 is responsible for bipolar spindle formation during early mitosis. Inhibition of Eg5 triggers the formation of monoastral spindles, leading to mitotic arrest that eventually causes apoptosis. There is increasing evidence that Eg5 constitutes a potential drug target for the development of cancer chemotherapeutics. The most advanced Eg5-targeting agent is ispinesib, which exhibits potent antitumour activity and is currently in multiple phase II clinical trials. In this study, the crystal structure of the Eg5 motor domain in complex with ispinesib, supported by kinetic and thermodynamic binding data, is reported. Ispinesib occupies the same induced-fit pocket in Eg5 as other allosteric inhibitors, making extensive hydrophobic interactions with the protein. The data for the Eg5-ADP-ispinesib complex suffered from pseudo-merohedral twinning and revealed translational noncrystallographic symmetry, leading to challenges in data processing, space-group assignment and structure solution as well as in refinement. These complications may explain the lack of available structural information for this important agent and its analogues. The present structure represents the best interpretation of these data based on extensive data-reduction, structure-solution and refinement trials.
人类驱动蛋白Eg5在有丝分裂早期负责双极纺锤体的形成。抑制Eg5会触发单星体纺锤体的形成，导致有丝分裂停滞，最终引发细胞凋亡。越来越多的证据表明，Eg5构成了开发癌症化疗药物的潜在靶点。最先进的Eg5靶向剂是艾司匹西布，它具有强大的抗肿瘤活性，目前正处于多项II期临床试验中。在本研究中，报告了与艾司匹西布复合的Eg5运动结构域的晶体结构，并得到了动力学和热力学结合数据的支持。艾司匹西布与其他变构抑制剂一样，占据Eg5中相同的诱导契合口袋，与蛋白质形成广泛的疏水相互作用。Eg5-ADP-艾司匹西布复合物的数据存在假单形孪晶，并显示出平移非晶体学对称性，这给数据处理、空间群归属、结构解析以及精修带来了挑战。这些复杂情况可能解释了关于这种重要药物及其类似物缺乏可用结构信息的原因。目前的结构是基于广泛的数据简化、结构解析和精修试验对这些数据的最佳解释。
