Discovery, structure, and function of filamentous 3-methylcrotonyl-CoA carboxylase
Discovery, structure, and function of filamentous 3-methylcrotonyl-CoA carboxylase
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DOI：
10.1016/j.str.2022.11.015
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发表时间：
2023-01-05
期刊：
影响因子：
5.7
通讯作者：
Zhou, Z. Hong
中科院分区：
文献类型：
--
作者：
Hu, Jason J.;Lee, Jane K. J.;Zhou, Z. Hong
3-甲基巴豆酰辅酶A羧化酶 (MCC) 是大多数生物体中亮氨酸分解代谢所必需的生物素依赖性线粒体酶。虽然重组细菌 MCC 的晶体结构已被表征，但天然 MCC 的结构和潜在聚合仍然难以捉摸。在这里，我们发现来自利什曼原虫 (LtMCC) 的天然 MCC 形成丝状，并使用冷冻电镜以 3.4、3.9 和 7.3 A 分辨率确定了不同丝状区域的结构。 a6b6 LtMCC 以扭曲堆叠结构组装，表现为长达 400 nm 的超分子棒。丝状 LtMCC 非共价结合生物素并且缺乏辅酶 A。丝通过将 a6b6 LtMCC 堆叠到末端 LtMCC 的外部 a-三聚体上而伸长。这种堆积固定了生物素羧化酶结构域，将酶隔离在非活性状态。我们的结果支持了一种新的 LtMCC 催化模型，称为双摆动域模型，并为羧化酶超家族及其他领域的聚合功能提供了新的线索。
3-methylcrotonyl-CoA carboxylase (MCC) is a biotin-dependent mitochondrial enzyme necessary for leucine catabolism in most organisms. While the crystal structure of recombinant bacterial MCC has been characterized, the structure and potential polymerization of native MCC remain elusive. Here, we discovered that native MCC from Leishmania tarentolae (LtMCC) forms filaments, and determined the struc-tures of different filament regions at 3.4, 3.9, and 7.3 A resolution using cryoEM. a6b6 LtMCCs assemble in a twisted-stacks architecture, manifesting as supramolecular rods up to 400 nm. Filamentous LtMCCs bind biotin non-covalently and lack coenzyme A. Filaments elongate by stacking a6b6 LtMCCs onto the exterior a-trimer of the terminal LtMCC. This stacking immobilizes the biotin carboxylase domains, sequestering the enzyme in an inactive state. Our results support a new model for LtMCC catalysis, termed the dual -swing-ing-domains model, and cast new light on the function of polymerization in the carboxylase superfamily and beyond.