Brautigam Chad A, Wynn R Max, Chuang Jacinta L, Machius Mischa, Tomchick Diana R, Chuang David T
Department of Biochemistry, The University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390, USA.
Structure. 2006 Mar;14(3):611-21. doi: 10.1016/j.str.2006.01.001. Epub 2006 Jan 26.
The 9.5 MDa human pyruvate dehydrogenase complex (PDC) utilizes the specific dihydrolipoamide dehydrogenase (E3) binding protein (E3BP) to tether the essential E3 component to the 60-meric core of the complex. Here, we report crystal structures of the binding domain (E3BD) of human E3BP alone and in complex with human E3 at 1.6 angstroms and 2.2 angstroms, respectively. The latter structure shows that residues from E3BD contact E3 across its 2-fold axis, resulting in one E3BD binding site on the E3 homodimer. Negligible conformational changes occur in E3BD upon its high-affinity binding to E3. Modifications of E3BD residues at the center of the E3BD/E3 interface impede E3 binding far more severely than those of residues on the periphery, validating the "hot spot" paradigm for protein interactions. A cluster of disease-causing E3 mutations located near the center of the E3BD/E3 interface prevents the efficient recruitment of these E3 variants by E3BP into the PDC, leading to the dysfunction of the PDC catalytic machine.
950 kDa的人丙酮酸脱氢酶复合物（PDC）利用特定的二氢硫辛酰胺脱氢酶（E3）结合蛋白（E3BP）将必需的E3组分连接到该复合物的60聚体核心上。在此，我们分别报道了人E3BP的结合结构域（E3BD）单独以及与E3形成复合物时的晶体结构，分辨率分别为1.6埃和2.2埃。后一种结构表明，E3BD的残基跨E3的2重轴与E3接触，在E3同型二聚体上形成一个E3BD结合位点。E3BD与E3高亲和力结合时，其构象变化可忽略不计。E3BD/E3界面中心处E3BD残基的修饰比外围残基的修饰更严重地阻碍E3结合，验证了蛋白质相互作用的“热点”范式。位于E3BD/E3界面中心附近的一组致病E3突变阻止E3BP将这些E3变体有效地募集到PDC中，导致PDC催化机制功能失调。
