PDF(Pubmed)
Abstract：
3-Methylcrotonyl-CoA carboxylase (MCC) catalyzes the two-step, biotin-dependent production of 3-methylglutaconyl-CoA, an essential intermediate in leucine catabolism. Given the critical metabolic role of MCC, deficiencies in this enzyme lead to organic aciduria, while its overexpression is linked to tumor development. MCC is a dodecameric enzyme composed of six copies of each α- and β-subunit. We present the cryo-EM structure of the endogenous MCC holoenzyme from Trypanosoma brucei in a non-filamentous state at 2.4 Å resolution. Biotin is covalently bound to the biotin carboxyl carrier protein domain of α-subunits and positioned in a non-canonical pocket near the active site of neighboring β-subunit dimers. Moreover, flexibility of key residues at α-subunit interfaces and loops enables pivoting of α-subunit trimers to partly reduce the distance between α- and β-subunit active sites, required for MCC catalysis. Our results provide a structural framework to understand the enzymatic mechanism of eukaryotic MCCs and to assist drug discovery against trypanosome infections.
摘要：
3-甲基巴豆酰基-CoA羧化酶（MCC）催化两步，依赖生物素的3-甲基戊二酰辅酶A的生产，亮氨酸分解代谢的重要中间体。鉴于MCC的关键代谢作用，这种酶的缺乏会导致有机酸尿，而其过度表达与肿瘤的发展有关。MCC是由每个α-和β-亚基的六个拷贝组成的十二聚体酶。我们以2.4bias分辨率呈现了非丝状状态的Brucei锥虫内源性MCC全酶的低温EM结构。生物素与α亚基的生物素羧基载体蛋白结构域共价结合，并位于邻近β亚基二聚体活性位点附近的非规范口袋中。此外，α-亚基界面和环的关键残基的灵活性使得α-亚基三聚体的旋转能够部分地减小α-和β-亚基活性位点之间的距离,MCC催化所需。我们的结果提供了一个结构框架，以了解真核MCC的酶促机制并帮助发现针对锥虫感染的药物。
