Allosteric motions in structures of yeast NAD+-specific isocitrate dehydrogenase
Allosteric motions in structures of yeast NAD+-specific isocitrate dehydrogenase
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DOI：
10.1074/jbc.m708719200
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发表时间：
2008-04-18
影响因子：
4.8
通讯作者：
McAlister-Henn, Lee
中科院分区：
文献类型：
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作者：
Taylor, Alexander B.;Hu, Gang;McAlister-Henn, Lee
线粒体 NAD(+) 特异性异柠檬酸脱氢酶 (IDH) 是响应细胞能量水平的生物合成和氧化途径通量的关键调节因子。在这里，我们展示了该酶家族真核成员的第一个结构，即来自酵母的变构异八聚体 NAD(+) 特异性 IDH，以三种形式：1) 无配体，2) 结合柠檬酸类似物，3) 结合柠檬酸 + AMP。这些结构揭示了配体与位于 IDH1 和 IDH2 亚基之间界面的同源但不同的调控和催化位点结合的分子基础，并定义了异二聚体和异八聚体中异四聚体之间的通讯途径。在未配位的 IDH 异八聚体的异四聚体界面处观察到的二硫键在配体结合形式中减少，表明氧化还原调节机制可能类似于通过磷酸化对非变构细菌 IDH 进行“开关”调节。结果强烈表明，真核 IDH 酶经过精心调整，以确保仅当异柠檬酸浓度升高时才会发生变构激活。
Mitochondrial NAD(+)-specific isocitrate dehydrogenases (IDHs) are key regulators of flux through biosynthetic and oxidative pathways in response to cellular energy levels. Here we present the first structures of a eukaryotic member of this enzyme family, the allosteric, hetero-octameric, NAD(+)-specific IDH from yeast in three forms: 1) without ligands, 2) with bound analog citrate, and 3) with bound citrate + AMP. The structures reveal the molecular basis for ligand binding to homologous but distinct regulatory and catalytic sites positioned at the interfaces between IDH1 and IDH2 subunits and define pathways of communication between heterodimers and heterotetramers in the hetero-octamer. Disulfide bonds observed at the heterotetrameric interfaces in the unliganded IDH hetero-octamer are reduced in the ligand-bound forms, suggesting a redox regulatory mechanism that may be analogous to the "on-off" regulation of non-allosteric bacterial IDHs via phosphorylation. The results strongly suggest that eukaryotic IDH enzymes are exquisitely tuned to ensure that allosteric activation occurs only when concentrations of isocitrate are elevated.