Span Ingrid, Wang Ke, Eisenreich Wolfgang, Bacher Adelbert, Zhang Yong, Oldfield Eric, Groll Michael
Center for Integrated Protein Science Munich, Chemistry Department, Technische Universität München , Lichtenbergstrasse 4, 85747 Garching, Germany.
J Am Chem Soc. 2014 Jun 4;136(22):7926-32. doi: 10.1021/ja501127j. Epub 2014 May 22.
(E)-1-Hydroxy-2-methylbut-2-enyl 4-diphosphate reductase (IspH) is a [Fe4S4] cluster-containing enzyme involved in isoprenoid biosynthesis in many bacteria as well as in malaria parasites and is an important drug target. Several inhibitors including amino and thiol substrate analogues, as well as acetylene and pyridine diphosphates, have been reported. Here, we investigate the mode of binding of four pyridine diphosphates to Escherichia coli IspH by using X-ray crystallography. In three cases, one of the iron atoms in the cluster is absent, but in the structure with (pyridin-3-yl)methyl diphosphate, the most potent pyridine-analogue inhibitor reported previously, the fourth iron of the [Fe4S4] cluster is present and interacts with the pyridine ring of the ligand. Based on the results of quantum chemical calculations together with the crystallographic results we propose a side-on η(2) coordination of the nitrogen and the carbon in the 2-position of the pyridine ring to the unique fourth iron in the cluster, which is in the reduced state. The X-ray structure enables excellent predictions using density functional theory of the (14)N hyperfine coupling and quadrupole coupling constants reported previously using HYSCORE spectroscopy, as well as providing a further example of the ability of such [Fe4S4]-containing proteins to form organometallic complexes.
（E）-1-羟基-2-甲基丁-2-烯基-4-二磷酸还原酶（IspH）是一种含[Fe4S4]簇的酶，参与许多细菌以及疟原虫的类异戊二烯生物合成，是一个重要的药物靶点。已经报道了几种抑制剂，包括氨基和硫醇底物类似物，以及乙炔和吡啶二磷酸盐。在这里，我们通过X射线晶体学研究了四种吡啶二磷酸盐与大肠杆菌IspH的结合模式。在三种情况下，簇中的一个铁原子缺失，但在与（吡啶-3-基）甲基二磷酸盐形成的结构中，即先前报道的最有效的吡啶类似物抑制剂，[Fe4S4]簇的第四个铁原子存在并与配体的吡啶环相互作用。基于量子化学计算结果以及晶体学结果，我们提出吡啶环2位的氮和碳与簇中处于还原态的独特第四个铁以侧基η(2)配位。X射线结构能够使用密度泛函理论对先前使用HYSCORE光谱报道的(14)N超精细耦合和四极耦合常数进行出色预测，同时也为这种含[Fe4S4]的蛋白质形成有机金属配合物的能力提供了另一个例子。
