Crystal structures of a novel ferric reductase from the hyperthermophilic archaeon Archaeoglobus fulgidus and its complex with NADP+
Crystal structures of a novel ferric reductase from the hyperthermophilic archaeon Archaeoglobus fulgidus and its complex with NADP+
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DOI：
10.1016/s0969-2126(01)00589-5
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发表时间：
2001-04-07
期刊：
影响因子：
5.7
通讯作者：
Rees, DC
中科院分区：
文献类型：
--
作者：
Chiu, HJ;Johnson, E;Rees, DC
背景资料：在过去十年中进行的研究表明，微生物将Fe（III）还原为Fe（II）是一个具有生物学意义的过程。闪烁古生菌铁还原酶（FeR）是首次报道的古生菌铁还原酶，它以NAD（P）H为电子供体催化黄素介导的三价铁还原反应。基于其催化活性，A.闪烁藻FeR类似于细菌和真核生物同化型的铁还原酶。然而，高细胞丰度的A. fulgidus FeR（约占总可溶性蛋白的0.75%）表明该酶在以三价铁为基础的呼吸途径中作为末端电子受体具有分解代谢作用[1]。通过多个同晶置换/反常衍射（MIRAS）定相方法在1.5埃分辨率下测定了含有结合FMN的fulgidus FeR，随后在1.65埃分辨率下测定了FeR的NADP（+）结合络合物。FeR由两个相同亚基的二聚体组成，尽管仅观察到一个亚基结合氧化还原辅因子。每个亚基围绕一个六链反平行β桶组织，该桶与来自脱硫弧菌的FMN结合蛋白同源。该折叠已被证明与铁氧还蛋白还原酶超家族的黄素结合结构域的环状排列形式有关。助理闪电铁还原酶与铁氧还蛋白还原酶超家族的进一步区别在于缺少用于结合NAD（P）H的Rossmann折叠结构域。相反，FeR使用其单一结构域来提供黄素和NAD（P）H结合位点。潜在的三价铁络合物的结合位点附近的辅因子bindingsites.Conclusions：这里描述的工作详细的酶FMN，酶FMN-NADP（+），并可能的酶FMN-铁的中间体，是存在于反应机制的结构。这些结构信息有助于确定特定残基在A还原三价铁络合物过程中的作用。闪烁的FeR.
Background: Studies performed within the last decade have indicated that microbial reduction of Fe(III) to Fe(II) is a biologically significant process. The ferric reductase (FeR) from Archaeoglobus fulgidus is the first reported archaeal ferric reductase and it catalyzes the flavin-mediated reduction of ferric iron complexes using NAD(P)H as the electron donor. Based on its catalytic activity, the A. fulgidus FeR resembles the bacterial and eukaryotic assimilatory type of ferric reductases. However, the high cellular abundance of the A. fulgidus FeR (similar to0.75% of the total soluble protein) suggests a catabolic role for this enzyme as the terminal electron acceptor in a ferric iron-based respiratory pathway [1].Results: The crystal structure of recombinant A. fulgidus FeR containing a bound FMN has been solved at 1.5 Angstrom resolution by multiple isomorphous replacement/anomalous diffraction (MIRAS) phasing methods, and the NADP(+)- bound complex of FeR was subsequently determined at 1.65 Angstrom resolution. FeR consists of a dimer of two identical subunits, although only one subunit has been observed to bind the redox cofactors. Each subunit is organized around a six-stranded antiparallel beta barrel that is homologous to the FMN binding protein from Desulfovibrio vulgaris. This fold has been shown to be related to a circularly permuted Version of the flavin binding domain of the ferredoxin reductase superfamily. The A. fulgidus ferric reductase is further distinguished from the ferredoxin reductase superfamily by the absence of a Rossmann fold domain that is used to bind the NAD(P)H. Instead, FeR uses its single domain to provide both the flavin and the NAD(P)H binding sites. Potential binding sites for ferric iron complexes are identified near the cofactor binding sites.Conclusions: The work described here details the structures of the enzyme-FMN, enzyme-FMN-NADP(+), and possibly the enzyme-FMN-iron intermediates that are present during the reaction mechanism. This structural information helps identify roles for specific residues during the reduction of ferric iron complexes by the A. fulgidus FeR.