Peters J W, Lanzilotta W N, Lemon B J, Seefeldt L C
Department of Chemistry and Biochemistry, Utah State University, Logan, UT 84322, USA.
Science. 1998 Dec 4;282(5395):1853-8. doi: 10.1126/science.282.5395.1853.
A three-dimensional structure for the monomeric iron-containing hydrogenase (CpI) from Clostridium pasteurianum was determined to 1.8 angstrom resolution by x-ray crystallography using multiwavelength anomalous dispersion (MAD) phasing. CpI, an enzyme that catalyzes the two-electron reduction of two protons to yield dihydrogen, was found to contain 20 gram atoms of iron per mole of protein, arranged into five distinct [Fe-S] clusters. The probable active-site cluster, previously termed the H-cluster, was found to be an unexpected arrangement of six iron atoms existing as a [4Fe-4S] cubane subcluster covalently bridged by a cysteinate thiol to a [2Fe] subcluster. The iron atoms of the [2Fe] subcluster both exist with an octahedral coordination geometry and are bridged to each other by three non-protein atoms, assigned as two sulfide atoms and one carbonyl or cyanide molecule. This structure provides insights into the mechanism of biological hydrogen activation and has broader implications for [Fe-S] cluster structure and function in biological systems.
利用多波长反常散射（MAD）相位法，通过X射线晶体学确定了巴氏梭菌单体含铁氢化酶（CpI）的三维结构，分辨率达到1.8埃。CpI是一种催化两个质子进行双电子还原以产生氢气的酶，发现每摩尔蛋白质含有20克原子铁，排列成五个不同的[Fe-S]簇。之前称为H簇的可能活性位点簇，被发现是六个铁原子的意外排列，以一个[4Fe-4S]立方烷亚簇形式存在，该亚簇通过一个半胱氨酸硫醇共价桥接到一个[2Fe]亚簇。[2Fe]亚簇的铁原子都以八面体配位几何结构存在，并通过三个非蛋白质原子相互桥接，这三个非蛋白质原子被指定为两个硫原子和一个羰基或氰化物分子。该结构为生物氢活化机制提供了见解，并且对生物系统中[Fe-S]簇的结构和功能具有更广泛的意义。
