Structural Study of Hydrogenase

本课题的主要目的是利用x射线结构分析方法对一种硫酸盐还原菌的Ni-Fe氢化酶的三维结构进行解析，并阐明其结构与功能之间的关系。氢化酶的结构在3.0分辨率下被解析，在1.8分辨率下被细化，r值为22.9%。该结构揭示了Ni-Fe活性中心的一个不寻常的配体。通过异常分散技术可以定位在Ni-Fe中心的铁原子有4个非蛋白配体。它们被划分为三个双原子分子和一个像硫一样的原子。从精细结构的立体化学几何和原子参数来看，这四种配体最可能的候选者是S=O，C=N，C=O和一种硫。红外光谱和热解质谱的数据支持了这种分配。在大亚基的羧基端发现了一个额外的Mg位点，距离Ni-Fe活性中心约13远。

The main purpose of this project is to solve the three-dimensional structure of Ni-Fe hydrogenase from one of the sulfate-reducing bacterium by X-ray structure analysis method, and clarify the relationship between the structure and function of it. The structure of the hydrogenase was solved at 3.0 resolution, and has been refined at 1.8 resolution with R-value of 22.9%. The structure reveals an unusual ligands in the Ni-Fe active center. The Fe atom, which was able to be assined in the Ni-Fe center by anoumalous dispersion technique has four non-protein ligands. They have been assigned as three diatomic molecules, and one atom like sulfur. From the stereochemical geometry and atomic parameters of the refined structure, the most probable candidates for the four ligands are S=O,C=N,C=O and one sulfur. The assignment is supported by the data obtained by infrared spectroscopy and pyrolysis-mass spectroscopy. One additional Mg site has been found in the carboxy-terminal region of the large subunit, which is approximately 13 distant from the Ni-Fe active center.