Organization of the cores of the mammalian pyruvate dehydrogenase complex formed by E2 and E2 plus the E3-binding protein and their capacities to bind the E1 and E3 components
Organization of the cores of the mammalian pyruvate dehydrogenase complex formed by E2 and E2 plus the E3-binding protein and their capacities to bind the E1 and E3 components
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DOI：
10.1074/jbc.m308172200
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发表时间：
2004-02-20
影响因子：
4.8
通讯作者：
Roche, TE
中科院分区：
文献类型：
--
作者：
Hiromasa, Y;Fujisawa, T;Roche, TE
哺乳动物丙酮酸脱氢酶复合物的二氢硫辛酰乙酰转移酶 (E2) 组分的亚基可以通过 E2 的 C 端 I 结构域在十二面体顶点处的缔合形成 60 聚体。在该内核结构的外部，E2具有丙酮酸脱氢酶组分(E1)结合结构域，随后是两个硫辛酰结构域，全部通过移动接头区域连接。哺乳动物丙酮酸脱氢酶复合物的组装核心结构还包括二氢硫辛酰脱氢酶（E3）结合蛋白（E3BP），其通过其C端I'结构域结合E2的I结构域。 E3BP类似地具有连接E3结合结构域和硫辛酰结构域的接头区域。 E2.E3BP的组成被认为是60个E2加类似于12个E3BP。我们准备了同质的人体成分。 E2 和 E2.E3BP 的 s(20,w) 值分别为 36 S 和 31.8 S。平衡沉降和小角X射线散射研究表明E2.E3BP的总质量低于E2，小角X射线散射表明E3在中心十二面体之外与E2.E3BP结合。在 E1 饱和水平存在的情况下，E2 的结合类似于 60 E1，最大沉积速度比 E2 快 64.4 +/- 1.5 S，而 E1 饱和的 E2.E3BP 最大沉积速度比 E2.E3BP 快 49.5 +/- 1.4 S。根据 E1 结合对沉降速率的影响，我们估计 E2.E3BP 结合的 E1（类似于 12）比 E2 结合的要少。较小的E2.E3BP质量和较低的结合E1的能力的发现支持较小的E3BP取代E2亚基而不是添加至60聚体。我们描述了一种替换模型，其中 E3BP 的 12 个 I' 结构域通过形成对称位于十二面体结构中的 6 个二聚体边缘来替换 E2 的 12 1 个结构域。每个 E2(48).E3BP(12) 质量结合 12 个 E3 二聚体，这与该模型一致。
The subunits of the dihydrolipoyl acetyltransferase (E2) component of mammalian pyruvate dehydrogenase complex can form a 60-mer via association of the C-terminal I domain of E2 at the vertices of a dodecahedron. Exterior to this inner core structure, E2 has a pyruvate dehydrogenase component (El)-binding domain followed by two lipoyl domains, all connected by mobile linker regions. The assembled core structure of mammalian pyruvate dehydrogenase complex also includes the dihydrolipoyl dehydrogenase (E3)-binding protein (E3BP) that binds the I domain of E2 by its C-terminal I' domain. E3BP similarly has linker regions connecting an E3-binding domain and a lipoyl domain. The composition of E2.E3BP was thought to be 60 E2 plus similar to12 E3BP. We have prepared homogenous human components. E2 and E2.E3BP have s(20,w) values of 36 S and 31.8 S, respectively. Equilibrium sedimentation and small angle x-ray scattering studies indicate that E2.E3BP has lower total mass than E2, and small angle x-ray scattering showed that E3 binds to E2.E3BP outside the central dodecahedron. In the presence of saturating levels of E1, E2 bound similar to60 E1 and maximally sedimented 64.4 +/- 1.5 S faster than E2, whereas E1-saturated E2.E3BP maximally sedimented 49.5 +/- 1.4 S faster than E2.E3BP. Based on the impact on sedimentation rates by bound E1, we estimate fewer E1 (similar to12) were bound by E2.E3BP than by E2. The findings of a smaller E2.E3BP mass and a lower capacity to bind El support the smaller E3BP substituting for E2 subunits rather than adding to the 60-mer. We describe a substitution model in which 12 I' domains of E3BP replace 12 1 domains of E2 by forming 6 dimer edges that are symmetrically located in the dodecahedron structure. Twelve E3 dimers were bound per E2(48).E3BP(12) mass, which is consistent with this model.