Conformational variability in structures of the nitrogenase iron proteins from Azotobacter vinelandii and Clostridium pasteurianum
Conformational variability in structures of the nitrogenase iron proteins from Azotobacter vinelandii and Clostridium pasteurianum
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DOI：
10.1006/jmbi.1998.1898
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发表时间：
1998-07-24
影响因子：
5.6
通讯作者：
Rees, DC
中科院分区：
文献类型：
--
作者：
Schlessman, JL;Woo, D;Rees, DC
固氮酶铁 (Fe) 蛋白在生物固氮过程中发挥多种功能，包括在底物还原过程中介导 ATP 水解和电子转移到固氮酶钼铁 (MoFe) 蛋白之间的机械必需耦合，以及参与 FeMo 辅因子到 MoFe 蛋白的生物合成和插入。为了建立解决铁蛋白多种功能的结构框架，分别以 2.2 埃和 1.93 埃的分辨率确定了来自维氏固氮菌和巴氏梭菌的铁蛋白的晶体结构。这两种铁蛋白在氨基酸序列和生化特性方面较为多样化。正如最初对分辨率为 2.9 埃的不同晶体形式的 A. vinelandii Fe 蛋白所描述的，二聚体 Fe 蛋白的每个亚基都采用与其他单核苷酸结合蛋白（如 G 蛋白）相关的多肽折叠，两个亚基通过 4Fe:4S 簇桥接。在 A. vinelandii 和 C. 巴斯德氏菌 Fe 蛋白的结构中观察到的亚基折叠和二聚体排列的总体相似性表明它们代表不与核苷酸或 MoFe 蛋白复合的游离 Fe 蛋白的构象。簇中的残基和核苷酸结合位点通过保守氢键、盐桥和水分子网络连接，这些网络可以在构象上耦合这些区域。在局部区域观察到显着的变异性，特别是在 4Fe:4S 簇和 MoFe-蛋白质结合表面附近，其在与 MoFe-蛋白质形成 ADP.AlF4 稳定复合物时改变构象。在 59 个铁蛋白序列的比对中鉴定出 140 个保守残基的核心，这可能有助于鉴定功能与非固氮系统中的铁蛋白相当的同源蛋白。 (C) 1998 年学术出版社。
The nitrogenase iron (Fe) protein performs multiple functions during biological nitrogen fixation, including mediating the mechanistically essential coupling between ATP hydrolysis and electron transfer to the nitrogenase molybdenum iron (MoFe) protein during substrate reduction, and participating in the biosynthesis and insertion of the FeMo-cofactor into the MoFe-protein. To establish a structural framework for addressing the diverse functions of Fe-protein, crystal structures of the Fe-proteins from Azotobacter vinelandii and Clostridium pasteurianum have been determined at resolutions of 2.2 Angstrom and 1.93 Angstrom, respectively. These two Fe-proteins are among the more diverse in terms of amino acid sequence and biochemical properties. As described initially for the A. vinelandii Fe-protein in a different crystal form at 2.9 Angstrom resolution, each subunit of the dimeric Fe-protein adopts a polypeptide fold related to other mononucleotide-binding proteins such as G-proteins, with the two subunits bridged by a 4Fe:4S cluster. The overall similarities in the subunit fold and dimer arrangement observed in the structures of the A. vinelandii and C. pasteurianum Fe-proteins indicate that they are representative of the conformation of free Fe-protein that is not in complex with nucleotide or the MoFe-protein. Residues in the cluster and nucleotide-binding sites are linked by a network of conserved hydrogen bonds, salt-bridges and water molecules that may conformationally couple these regions. Significant variability is observed in localized regions, especially near the 4Fe:4S cluster and the MoFe-protein binding surface, that change conformation upon formation of the ADP.AlF4- stabilized complex with the MoFe-protein. A core of 140 conserved residues is identified in an alignment of 59 Fe-protein sequences that may be useful for the identification of homologous proteins with functions comparable to that of Fe-protein in non-nitrogen fixing systems. (C) 1998 Academic Press.