Crystal Structures Reveal that the Reaction Mechanism of Imidazoleglycerol-Phosphate Dehydratase Is Controlled by Switching Mn(II) Coordination.
Crystal Structures Reveal that the Reaction Mechanism of Imidazoleglycerol-Phosphate Dehydratase Is Controlled by Switching Mn(II) Coordination.
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DOI：
10.1016/j.str.2015.05.012
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发表时间：
2015-07-07
期刊：
影响因子：
--
通讯作者：
Rice DW
中科院分区：
文献类型：
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作者：
Bisson C;Britton KL;Sedelnikova SE;Rodgers HF;Eadsforth TC;Viner RC;Hawkes TR;Baker PJ;Rice DW
咪唑甘油磷酸脱氢酶（imidazoleglycerol-phosphatase，IGPD）在组氨酸生物合成过程中催化咪唑甘油磷酸（imidazoleglycerolphosphate，IGP）脱水生成3-（1H-咪唑-4-基）-2-氧代丙基磷酸二氢盐。作为除草剂设计计划的一部分，我们已经确定了一系列高分辨率的晶体结构的非活性突变体IGPD2从拟南芥与IGP的复杂。的结构表示快照的酶被困在不同阶段的催化循环，并显示如何基板结合触发开关的活性位点Mn（II）之间的六个和五个配位物种的配位状态。这种开关是关键的启动催化活性位点，通过促进形成一个高能量的咪唑中间体。这项工作不仅为IGPD中主导催化的分子过程提供了证据，而且还描述了金属配位的操纵如何与催化中的离散步骤联系起来，展示了金属酶利用金属离子的独特性质使其化学多样化的一种方式。IGPD与IGP形成开放和封闭的复合物，以两种不同的构象结合Mn（II）通过在6-和5-配位状态之间切换来控制催化作用。配体耗尽的5-配位Mn（II）有助于形成咪唑酯中间体酶和底物构象变化是产物形成所必需的。确定的结构，描述了IGPD的反应机制，显示了酶如何利用底物结合能在催化中心产生配体耗尽的Mn（II）。酶-底物复合物中的构象变化和配位化学中的开关控制催化中的连续步骤。
Imidazoleglycerol-phosphate dehydratase (IGPD) catalyzes the Mn(II)-dependent dehydration of imidazoleglycerol phosphate (IGP) to 3-(1H-imidazol-4-yl)-2-oxopropyl dihydrogen phosphate during biosynthesis of histidine. As part of a program of herbicide design, we have determined a series of high-resolution crystal structures of an inactive mutant of IGPD2 from Arabidopsis thaliana in complex with IGP. The structures represent snapshots of the enzyme trapped at different stages of the catalytic cycle and show how substrate binding triggers a switch in the coordination state of an active site Mn(II) between six- and five-coordinate species. This switch is critical to prime the active site for catalysis, by facilitating the formation of a high-energy imidazolate intermediate. This work not only provides evidence for the molecular processes that dominate catalysis in IGPD, but also describes how the manipulation of metal coordination can be linked to discrete steps in catalysis, demonstrating one way that metalloenzymes exploit the unique properties of metal ions to diversify their chemistry. IGPD forms open and closed complexes with IGP bound in two distinct conformations Mn(II) controls catalysis by switching between 6- and 5-coordination states A ligand-depleted 5-coordinate Mn(II) aids formation of the imidazolate intermediate Enzyme and substrate conformational changes are required for product formation Bisson et al. determined structures that describe the reaction mechanism of IGPD, showing how the enzyme harnesses substrate binding energy to generate a ligand-depleted Mn(II) at the catalytic center. Conformational changes in the enzyme-substrate complex and switches in coordination chemistry control successive steps in catalysis.