PDF(Pubmed)
Abstract：
Cryptophycins are microtubule-targeting agents (MTAs) that belong to the most potent antimitotic compounds known to date; however, their exact molecular mechanism of action remains unclear. Here, we present the 2.2 Å resolution X-ray crystal structure of a potent cryptophycin derivative bound to the αβ-tubulin heterodimer. The structure addresses conformational issues present in a previous 3.3 Å resolution cryo-electron microscopy structure of cryptophycin-52 bound to the maytansine site of β-tubulin. It further provides atomic details on interactions of cryptophycins, which had not been described previously, including ones that are in line with structure-activity relationship studies. Interestingly, we discovered a second cryptophycin-binding site that involves the T5-loop of β-tubulin, a critical secondary structure element involved in the exchange of the guanosine nucleotide and in the formation of longitudinal tubulin contacts in microtubules. Cryptophycins are the first natural ligands found to bind to this new \"βT5-loop site\" that bridges the maytansine and vinca sites. Our results offer unique avenues to rationally design novel MTAs with the capacity to modulate T5-loop dynamics and to simultaneously engage multiple β-tubulin binding sites.
摘要：
隐霉素是微管靶向剂（MTA），属于迄今为止已知的最有效的抗有丝分裂化合物；然而，其确切的分子作用机制尚不清楚.这里,我们展示了与αβ-微管蛋白异源二聚体结合的有效隐霉素衍生物的2.2µ分辨率X射线晶体结构。该结构解决了与β-微管蛋白的美登素位点结合的隐霉素52的先前3.3µ分辨率低温电子显微镜结构中存在的构象问题。它进一步提供了关于隐藻蛋白相互作用的原子细节，以前没有描述过，包括符合结构-活动关系(SAR)研究的研究。有趣的是,我们发现了第二个涉及β-微管蛋白T5环的隐蛋白结合位点，参与鸟苷核苷酸交换和微管中纵向微管蛋白接触形成的关键二级结构元件。隐藻蛋白是第一个发现与这个新的“βT5环位点”结合的天然配体，它桥接了美登素和长春花位点。我们的结果为合理设计新型MTA提供了独特的途径，该MTA具有调节T5环动力学并同时参与多个β-微管蛋白结合位点的能力。
