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Crystal Structures of a Novel Ferric Reductase from the Hyperthermophilic Archaeon Archaeoglobus fulgidus and Its Complex with NADP+

Chiu, Hsiu-Ju and Johnson, Eric and Schröder, Imke and Rees, Douglas C. (2001) Crystal Structures of a Novel Ferric Reductase from the Hyperthermophilic Archaeon Archaeoglobus fulgidus and Its Complex with NADP+. Structure, 9 (4). pp. 311-319. ISSN 0969-2126. doi:10.1016/S0969-2126(01)00589-5.

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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 (∼0.75% 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 Å resolution by multiple isomorphous replacement/anomalous diffraction (MIRAS) phasing methods, and the NADP+- bound complex of FeR was subsequently determined at 1.65 Å 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 β 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.

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URLURL TypeDescription DOIArticle
Rees, Douglas C.0000-0003-4073-1185
Additional Information:© 2001 Elsevier Science Ltd. Received: December 18, 2000; Revised: January 31, 2001; Accepted: February 20, 2001. We thank the reviewers for their insightful comments. This work was supported by National Institutes of Health HL-16251 (I. S.) and National Institutes of Health GM-45162 (D. C. R). This work is based on research conducted at the Stanford Synchrotron Radiation Laboratory (SSRL), which is funded by the Department of Energy, Office of Basic Energy Sciences, and the National Institutes of Health.
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Department of Energy (DOE)UNSPECIFIED
Subject Keywords:ferric reductase; flavoproteins; ferredoxin reductase superfamily; iron metabolism; NAD(P)H:flavin oxidoreductase
Issue or Number:4
Record Number:CaltechAUTHORS:20150108-153854607
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Official Citation:Hsiu-Ju Chiu, Eric Johnson, Imke Schröder, Douglas C. Rees, Crystal Structures of a Novel Ferric Reductase from the Hyperthermophilic Archaeon Archaeoglobus fulgidus and Its Complex with NADP+, Structure, Volume 9, Issue 4, April 2001, Pages 311-319, ISSN 0969-2126, (
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ID Code:53409
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Deposited On:13 Jan 2015 18:47
Last Modified:10 Nov 2021 20:01

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