CRYSTALLOGRAPHIC STRUCTURE OF THE NITROGENASE IRON PROTEIN FROM AZOTOBACTER-VINELANDII
CRYSTALLOGRAPHIC STRUCTURE OF THE NITROGENASE IRON PROTEIN FROM AZOTOBACTER-VINELANDII
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DOI：
10.1126/science.1529353
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发表时间：
1992-09-18
期刊：
影响因子：
56.9
通讯作者：
REES, DC
中科院分区：
文献类型：
--
作者：
GEORGIADIS, MM;KOMIYA, H;REES, DC
固氮酶系统在固氮过程中催化ATP（三磷酸腺苷）依赖性的二氮还原为氨。固氮酶由两种蛋白质组成：铁（Fe）-蛋白质，其将ATP水解与电子转移偶联，以及铼-铁（MoFe）-蛋白质，其含有二氮结合位点。为了解决ATP在固氮中的作用，已在2.9埃（埃）分辨率下测定了棕色固氮菌固氮酶铁蛋白的晶体结构。铁蛋白是由两个相同的亚基组成的二聚体，它们协调一个单一的4Fe：4S簇。每个亚基折叠为单个α/β型结构域，其通过来自每个亚基的两个半胱氨酸一起对称地连接表面暴露的4Fe：4S簇。单个结合的ADP（腺苷二磷酸）分子位于两个亚基之间的界面区域。由于该核苷酸的磷酸基团距离4Fe：4S簇约20埃，因此ATP水解和电子转移不太可能直接耦合。相反，它出现的核苷酸和集群网站之间的相互作用必须间接耦合发生在亚基界面的变构变化。铁蛋白的蛋白质构象和核苷酸水解之间的耦合表现出一般的相似性的H-Ras p21和recA蛋白，最近已在结构上的特点。铁蛋白结构可能与其他生化能量转导系统的功能有关，这些系统含有两个核苷酸结合位点，包括膜转运蛋白。
The nitrogenase enzyme system catalyzes the ATP (adenosine triphosphate)-dependent reduction of dinitrogen to ammonia during the process of nitrogen fixation. Nitrogenase consists of two proteins: the iron (Fe)-protein, which couples hydrolysis of ATP to electron transfer, and the molybdenum-iron (MoFe)-protein, which contains the dinitrogen binding site. In order to address the role of ATP in nitrogen fixation, the crystal structure of the nitrogenase Fe-protein from Azotobacter vinelandii has been determined at 2.9 angstrom (angstrom) resolution. Fe-protein is a dimer of two identical subunits that coordinate a single 4Fe:4S cluster. Each subunit folds as a single alpha/beta-type domain, which together symmetrically ligate the surface exposed 4Fe:4S cluster through two cysteines from each subunit. A single bound ADP (adenosine diphosphate) molecule is located in the interface region between the two subunits. Because the phosphate groups of this nucleotide are approximately 20 angstrom from the 4Fe:4S cluster, it is unlikely that ATP hydrolysis and electron transfer are directly coupled. Instead, it appears that interactions between the nucleotide and cluster sites must be indirectly coupled by allosteric changes occurring at the subunit interface. The coupling between protein conformation and nucleotide hydrolysis in Fe-protein exhibits general similarities to the H-Ras p21 and recA proteins that have been recently characterized structurally. The Fe-protein structure may be relevant to the functioning of other biochemical energy-transducing systems containing two nucleotide-binding sites, including membrane transport proteins.