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Abstract
Although the gastrointestinal tract is regarded as mainly anoxic, low O2 tension is present in the gut and tends to increase following antibiotic-induced disruption of the host microbiota. Two decreasing O2 gradients are observed, a longitudinal one from the small to the large intestine and a second one from the intestinal epithelium toward the colon lumen. Thus, O2 concentration fluctuations within the gastrointestinal tract are a challenge for anaerobic bacteria such as C. difficile. This enteropathogen has developed efficient strategies to detoxify O2. In this work, we identified reverse rubrerythrins and flavodiiron proteins as key actors for O2 tolerance in C. difficile. These enzymes are responsible for the reduction of O2 protecting C. difficile vegetative cells from associated damages. Original and complex detoxification pathways involving O2-reductases are crucial in the ability of C. difficile to tolerate O2 and survive to O2 concentrations encountered in the gastrointestinal tract. Clostridioides difficile is a major cause of diarrhea associated with antibiotherapy. After germination of C. difficile spores in the small intestine, vegetative cells are exposed to low oxygen (O2) tensions. While considered strictly anaerobic, C. difficile is able to grow in nonstrict anaerobic conditions (1 to 3% O2) and tolerates brief air exposure indicating that this bacterium harbors an arsenal of proteins involved in O2 detoxification and/or protection. Tolerance of C. difficile to low O2 tensions requires the presence of the alternative sigma factor, σB, involved in the general stress response. Among the genes positively controlled by σB, four encode proteins likely involved in O2 detoxification: two flavodiiron proteins (FdpA and FdpF) and two reverse rubrerythrins (revRbr1 and revRbr2). As previously observed for FdpF, we showed that both purified revRbr1 and revRbr2 harbor NADH-linked O2- and H2O2-reductase activities in vitro, while purified FdpA mainly acts as an O2-reductase. The growth of a fdpA mutant is affected at 0.4% O2, while inactivation of both revRbrs leads to a growth defect above 0.1% O2. O2-reductase activities of these different proteins are additive since the quadruple mutant displays a stronger phenotype when exposed to low O2 tensions compared to the triple mutants. Our results demonstrate a key role for revRbrs, FdpF, and FdpA proteins in the ability of C. difficile to grow in the presence of physiological O2 tensions such as those encountered in the colon.
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Tavares NK, Stracey N, Brunold TC, Escalante-Semerena JC. The l-Thr Kinase/l-Thr-Phosphate Decarboxylase (CobD) Enzyme from Methanosarcina mazei Gö1 Contains Metallocenters Needed for Optimal Activity. Biochemistry 2019; 58:3260-3279. [PMID: 31268299 PMCID: PMC6667302 DOI: 10.1021/acs.biochem.9b00268] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The MM2060 (cobD) gene from Methanosarcina mazei strain Gö1 encodes a protein (MmCobD) with l-threonine kinase (PduX) and l-threonine-O-3-phosphate decarboxylase (CobD) activities. In addition to the unexpected l-Thr kinase activity, MmCobD has an extended carboxy-terminal (C-terminal) region annotated as a putative metal-binding zinc finger-like domain. Here, we demonstrate that the C-terminus of MmCobD is a ferroprotein containing ∼25 non-heme iron atoms per monomer of protein. The absence of the C-terminus substantially reduces, but does not abolish, enzymatic activities in vitro and in vivo. Single-residue substitutions of C-terminal putative Fe-binding cysteinyl and histidinyl residues resulted in the loss of Fe and changes in enzyme activity levels. Salmonella enterica ΔpduX and ΔcobD strains were used as heterologous hosts to assess coenzyme B12 biosynthesis as a function of 17 MmCobD variants tested. Some of the latter displayed 5-fold higher enzymatic activity in vitro and enhanced the growth rate of the S. enterica strains that synthesized them. Most of the MmCobD variants tested were up to 6-fold less active in vitro and supported slow growth rates of the S. enterica strains that synthesized them; some substitutions abolished enzyme activity. MmCobD exhibited an ultraviolet-visible absorption spectrum consistent with [4Fe-4S] clusters that appeared to be susceptible to oxidation by H2O2 and reduction by sodium dithionite. The presence of FeS clusters in MmCobD was corroborated by electron paramagnetic resonance and magnetic circular dichroism studies. Collectively, our results suggest that MmCobD contains one or more diamagnetic [4Fe-4S]2+ center(s) that may play a structural or regulatory role.
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Affiliation(s)
- Norbert K. Tavares
- Department of Microbiology, University of Georgia, Athens, Georgia 30602, USA
| | - Nuru Stracey
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706 USA
| | - Thomas C Brunold
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706 USA
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3
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The multidomain flavodiiron protein from Clostridium difficile 630 is an NADH:oxygen oxidoreductase. Sci Rep 2018; 8:10164. [PMID: 29977056 PMCID: PMC6033852 DOI: 10.1038/s41598-018-28453-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Accepted: 06/20/2018] [Indexed: 01/05/2023] Open
Abstract
Flavodiiron proteins (FDPs) are enzymes with a minimal core of two domains: a metallo-β-lactamase-like, harbouring a diiron center, and a flavodoxin, FMN containing, domains. FDPs are O2 or NO reducing enzymes; for many pathogens, they help mitigate the NO produced by the immune system of the host, and aid survival during fluctuating concentrations concentrations of oxygen. FDPs have a mosaic structure, being predicted to contain multiple extra domains. Clostridium difficile, a threatening human pathogen, encodes two FDPs: one with the two canonical domains, and another with a larger polypeptide chain of 843 amino acids, CD1623, with two extra domains, predicted to be a short-rubredoxin-like and an NAD(P)H:rubredoxin oxidoreductase. This multi-domain protein is the most complex FDP characterized thus far. Each of the predicted domains was characterized and the presence of the predicted cofactors confirmed by biochemical and spectroscopic analysis. Results show that this protein operates as a standalone FDP, receiving electrons directly from NADH, and reducing oxygen to water, precluding the need for extra partners. CD1623 displayed negligible NO reductase activity, and is thus considered an oxygen selective FDP, that may contribute to the survival of C. difficile in the human gut and in the environment.
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Miriani M, Iametti S, Kurtz DM, Bonomi F. Rubredoxin refolding on nanostructured hydrophobic surfaces: evidence for a new type of biomimetic chaperones. Proteins 2014; 82:3154-62. [PMID: 25143010 DOI: 10.1002/prot.24675] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Revised: 08/04/2014] [Accepted: 08/11/2014] [Indexed: 11/08/2022]
Abstract
Rubredoxins (Rds) are small proteins containing a tetrahedral Fe(SCys)4 site. Folded forms of metal free Rds (apoRds) show greatly impaired ability to incorporate iron compared with chaotropically unfolded apoRds. In this study, formation of the Rd holoprotein (holoRd) on addition of iron to a structured, but iron-uptake incompetent apoRd was investigated in the presence of polystyrene nanoparticles (NP). In our rationale, hydrophobic contacts between apoRd and the NP surface would expose protein regions (including ligand cysteines) buried in the structured apoRd, allowing iron incorporation and folding to the native holoRd. Burial of the hydrophobic regions in the folded holoRd would allow its detachment from the NP surface. We found that both rate and yield of holoRd formation increased significantly in the presence of NP and were influenced by the NP concentration and size. Rates and yields had an optimum at "catalytic" NP concentrations (0.2 g/L NP) when using relatively small NP (46 nm diameter). At these optimal conditions, only a fraction of the apoRd was bound to the NP, consistent with the occurrence of turnover events on the NP surface. Lower rates and yields at higher NP concentrations or when using larger NP (200 nm) suggest that steric effects and molecular crowding on the NP surface favor specific "iron-uptake-competent" conformations of apoRd on the NP surface. This bio-mimetic chaperone system may be applicable to other proteins requiring an unfolding step before cofactor-triggered refolding, particularly when over-expressed under limited cofactor accessibility.
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Affiliation(s)
- Matteo Miriani
- Section of Chemistry and Biomolecular Sciences, DeFENS, University of Milan, Milan, Italy
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5
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Hathazi D, Mot AC, Vaida A, Scurtu F, Lupan I, Fischer-Fodor E, Damian G, Kurtz DM, Silaghi-Dumitrescu R. Oxidative protection of hemoglobin and hemerythrin by cross-linking with a nonheme iron peroxidase: potentially improved oxygen carriers for use in blood substitutes. Biomacromolecules 2014; 15:1920-7. [PMID: 24716617 DOI: 10.1021/bm5004256] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The nonheme peroxidase, rubrerythrin, shows the ability to reduce hydrogen peroxide to water without involving strongly oxidizing and free-radical-creating powerful oxidants such as compounds I and II [formally Fe(IV)] formed in peroxidases and catalases. Rubrerythrin could, therefore, be a useful ingredient in protein-based artificial oxygen carriers. Here, we report that the oxygen-carrying proteins, hemoglobin (Hb) and hemerythrin (Hr), can each be copolymerized with rubrerythrin using glutaraldehyde yielding high molecular weight species. These copolymers show additional peroxidase activity compared to Hb-only and Hr-only polymers, respectively and also generate lower levels of free radicals in reactions that involve hydrogen peroxide. Tests on human umbilical vein endothelial cells (HUVEC) reveal slightly better performance of the Rbr copolymers compared to controls, as measured at 24 h, but not at later times.
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Affiliation(s)
- Denisa Hathazi
- Faculty of Chemistry and Chemical Engineering, "Babes-Bolyai" University , 11 Arany Janos St., Cluj-Napoca, Romania
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6
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Zanello P. The competition between chemistry and biology in assembling iron–sulfur derivatives. Molecular structures and electrochemistry. Part I. {Fe(SγCys)4} proteins. Coord Chem Rev 2013. [DOI: 10.1016/j.ccr.2013.02.006] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Bikas R, Hosseini-Monfared H, Zoppellaro G, Herchel R, Tucek J, Owczarzak AM, Kubicki M, Zboril R. Synthesis, structure, magnetic properties and theoretical calculations of methoxy bridged dinuclear iron(iii) complex with hydrazone based O,N,N-donor ligand. Dalton Trans 2013; 42:2803-12. [DOI: 10.1039/c2dt31751f] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
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8
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Pereira AS, Timóteo CG, Guilherme M, Folgosa F, Naik SG, Duarte AG, Huynh BH, Tavares P. Spectroscopic evidence for and characterization of a trinuclear ferroxidase center in bacterial ferritin from Desulfovibrio vulgaris Hildenborough. J Am Chem Soc 2012; 134:10822-32. [PMID: 22681596 PMCID: PMC3390943 DOI: 10.1021/ja211368u] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Ferritins are ubiquitous and can be found in practically all organisms that utilize Fe. They are composed of 24 subunits forming a hollow sphere with an inner cavity of ~80 Å in diameter. The main function of ferritin is to oxidize the cytotoxic Fe(2+) ions and store the oxidized Fe in the inner cavity. It has been established that the initial step of rapid oxidation of Fe(2+) (ferroxidation) by H-type ferritins, found in vertebrates, occurs at a diiron binding center, termed the ferroxidase center. In bacterial ferritins, however, X-ray crystallographic evidence and amino acid sequence analysis revealed a trinuclear Fe binding center comprising a binuclear Fe binding center (sites A and B), homologous to the ferroxidase center of H-type ferritin, and an adjacent mononuclear Fe binding site (site C). In an effort to obtain further evidence supporting the presence of a trinuclear Fe binding center in bacterial ferritins and to gain information on the states of the iron bound to the trinuclear center, bacterial ferritin from Desulfovibrio vulgaris (DvFtn) and its E130A variant was loaded with substoichiometric amounts of Fe(2+), and the products were characterized by Mössbauer and EPR spectroscopy. Four distinct Fe species were identified: a paramagnetic diferrous species, a diamagnetic diferrous species, a mixed valence Fe(2+)Fe(3+) species, and a mononuclear Fe(2+) species. The latter three species were detected in the wild-type DvFtn, while the paramagnetic diferrous species was detected in the E130A variant. These observations can be rationally explained by the presence of a trinuclear Fe binding center, and the four Fe species can be properly assigned to the three Fe binding sites. Further, our spectroscopic data suggest that (1) the fully occupied trinuclear center supports an all ferrous state, (2) sites B and C are bridged by a μ-OH group forming a diiron subcenter within the trinuclear center, and (3) this subcenter can afford both a mixed valence Fe(2+)Fe(3+) state and a diferrous state. Mechanistic insights provided by these new findings are discussed and a minimal mechanistic scheme involving O-O bond cleavage is proposed.
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Affiliation(s)
- Alice S. Pereira
- Requimte/CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Quinta da Torre, 2829-516 Caparica, Portugal
| | - Cristina G. Timóteo
- Requimte/CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Quinta da Torre, 2829-516 Caparica, Portugal
| | - Márcia Guilherme
- Requimte/CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Quinta da Torre, 2829-516 Caparica, Portugal
| | - Filipe Folgosa
- Requimte/CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Quinta da Torre, 2829-516 Caparica, Portugal
| | - Sunil G. Naik
- Department of Physics, Emory University, Atlanta, GA 30322, USA
| | - Américo G. Duarte
- Requimte/CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Quinta da Torre, 2829-516 Caparica, Portugal
| | - Boi Hanh Huynh
- Department of Physics, Emory University, Atlanta, GA 30322, USA
| | - Pedro Tavares
- Requimte/CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Quinta da Torre, 2829-516 Caparica, Portugal
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Cooley RB, Arp DJ, Karplus PA. Symerythrin structures at atomic resolution and the origins of rubrerythrins and the ferritin-like superfamily. J Mol Biol 2011; 413:177-94. [PMID: 21872605 DOI: 10.1016/j.jmb.2011.08.019] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2011] [Revised: 08/08/2011] [Accepted: 08/09/2011] [Indexed: 11/25/2022]
Abstract
Rubrerythrins are diiron-containing peroxidases that belong to the ferritin-like superfamily (FLSF). Here, we describe the structures of symerythrin, a novel rubrerythrin variant from the oxygenic phototroph Cyanophora paradoxa, at 1.20-1.40 Å resolution in three different states: diferric, azide-bound diferric and chemically reduced. The symerythrin metallocenter has a unique eighth ligating residue compared to rubrerythrin-an additional glutamate inserted into helix A of the four-helix bundle that resides on a π-helical segment. Otherwise, the diferric metallocenter structure is highly similar to that of characterized rubrerythrins. Azide binds the diferric center in a μ-1,1 orientation similar to how peroxide binds to diferric rubrerythrin. The structure of the diferrous metallocenter shows heterogeneity that we ascribe to the acidic pH of the crystals. In what we consider the neutral pH conformation, reduction causes a 2.0-Å shift in Fe1 and the toggling of a Glu to a His ligand, as seen with rubrerythrins. The function of symerythrin remains unknown, but preliminary tests showing oxidase and peroxidase activities and the similarities of its metallocenter to other rubrerythrins suggest similar functionalities between the two despite the additional ligating glutamate in symerythrin. Of particular interest is the high internal symmetry of symerythrin, which supports the notion that its core four-helix bundle was formed by the gene duplication and fusion of a two-helix peptide. Sequence comparisons with another family in the FLSF that also has notable internal symmetry provide compelling evidence that, contrary to previous assumptions, there have been multiple gene fusion events that have generated the single-chain FLSF fold.
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Affiliation(s)
- Richard B Cooley
- Department of Biochemistry and Biophysics, 2011 Ag and Life Sciences Building, Oregon State University, Corvallis, OR 97331, USA
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10
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Dillard BD, Demick JM, Adams MWW, Lanzilotta WN. A cryo-crystallographic time course for peroxide reduction by rubrerythrin from Pyrococcus furiosus. J Biol Inorg Chem 2011; 16:949-59. [PMID: 21647777 DOI: 10.1007/s00775-011-0795-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2011] [Accepted: 05/16/2011] [Indexed: 11/28/2022]
Abstract
High-resolution crystal structures of Pyrococcus furiosus rubrerythrin (PfRbr) in the resting (all-ferrous) state and at time points following exposure of the crystals to hydrogen peroxide are reported. This approach was possible because of the relativity slow turnover of PfRbr at room temperature. To this end, we were able to perform time-dependent peroxide treatment of the fully reduced enzyme, under strictly anaerobic conditions, in the crystalline state. In this work we demonstrate, for the first time, that turnover of a thermophilic rubrerythrin results in approximately 2-Å movement of one iron atom in the diiron site from a histidine to a carboxylate ligand. These results confirm that, despite the domain-swapped architecture, the hyperthermophilic rubrerythrins also utilize the classic combination of iron sites together with redox-dependent iron toggling to selectively reduce hydrogen peroxide over dioxygen. In addition, we have identified previously unobserved intermediates in the reaction cycle and observed structural changes that may explain the enzyme precipitation observed for the all-iron form of PfRbr upon oxidation to the all-ferric state.
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Affiliation(s)
- Bret D Dillard
- Department of Biochemistry and Molecular Biology, The Center for Metalloenzyme Studies, University of Georgia, Athens, GA 30602, USA
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11
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Pinto AF, Todorovic S, Hildebrandt P, Yamazaki M, Amano F, Igimi S, Romão CV, Teixeira M. Desulforubrerythrin from Campylobacter jejuni, a novel multidomain protein. J Biol Inorg Chem 2010; 16:501-10. [PMID: 21170562 DOI: 10.1007/s00775-010-0749-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2010] [Accepted: 12/01/2010] [Indexed: 10/18/2022]
Abstract
A novel multidomain metalloprotein from Campylobacter jejuni was overexpressed in Escherichia coli, purified, and extensively characterized. This protein is isolated as a homotetramer of 24-kDa monomers. According to the amino acid sequence, each monomer was predicted to contain three structural domains: an N-terminal desulforedoxin-like domain, followed by a four-helix bundle domain harboring a non-sulfur μ-oxo diiron center, and a rubredoxin-like domain at the C-terminus. The three predicted iron sites were shown to be present and were studied by a combination of UV-vis, EPR, and resonance Raman spectroscopies, which allowed the determination of the electronic and redox properties of each site. The protein contains two FeCys(4) centers with reduction potentials of +240 mV (desulforedoxin-like center) and +185 mV (rubredoxin-like center). These centers are in the high-spin configuration in the as-isolated ferric form. The protein further accommodates a μ-oxo-bridged diiron site with reduction potentials of +270 and +235 mV for the two sequential redox transitions. The protein is rapidly reoxidized by hydrogen peroxide and has a significant NADH-linked hydrogen peroxide reductase activity of 1.8 μmol H(2)O(2) min(-1) mg(-1). Owing to its building blocks and its homology to the rubrerythrin family, the protein is named desulforubrerythrin. It represents a novel example of the large diversity of the organization of domains exhibited by this enzyme family.
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Affiliation(s)
- Ana F Pinto
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Avenida da República (EAN), 2780-157, Oeiras, Portugal
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12
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Riebe O, Fischer RJ, Wampler DA, Kurtz DM, Bahl H. Pathway for H2O2 and O2 detoxification in Clostridium acetobutylicum. MICROBIOLOGY-SGM 2009; 155:16-24. [PMID: 19118342 DOI: 10.1099/mic.0.022756-0] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
An unusual non-haem diiron protein, reverse rubrerythrin (revRbr), is known to be massively upregulated in response to oxidative stress in the strictly anaerobic bacterium Clostridium acetobutylicum. In the present study both in vivo and in vitro results demonstrate an H2O2 and O2 detoxification pathway in C. acetobutylicum involving revRbr, rubredoxin (Rd) and NADH : rubredoxin oxidoreductase (NROR). RevRbr exhibited both NADH peroxidase (NADH : H2O2 oxidoreductase) and NADH oxidase (NADH : O2 oxidoreductase) activities in in vitro assays using NROR as the electron-transfer intermediary from NADH to revRbr. Rd increased the NADH consumption rate by serving as an intermediary electron-transfer shuttle between NROR and revRbr. While H2O2 was found to be the preferred substrate for revRbr, its relative oxidase activity was found to be significantly higher than that reported for other Rbrs. A revRbr-overexpressing strain of C. acetobutylicum showed significantly increased tolerance to H2O2 and O2 exposure. RevRbr thus appears to protect C. acetobutylicum against oxidative stress by functioning as the terminal component of an NADH peroxidase and NADH oxidase.
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Affiliation(s)
- Oliver Riebe
- Division of Microbiology, Institute of Biological Sciences, University of Rostock, Albert-Einstein-Str. 3, D-18051 Rostock, Germany
| | - Ralf-Jörg Fischer
- Division of Microbiology, Institute of Biological Sciences, University of Rostock, Albert-Einstein-Str. 3, D-18051 Rostock, Germany
| | - David A Wampler
- Department of Chemistry, University of Texas at San Antonio, San Antonio, TX 78249, USA
| | - Donald M Kurtz
- Department of Chemistry, University of Texas at San Antonio, San Antonio, TX 78249, USA
| | - Hubert Bahl
- Division of Microbiology, Institute of Biological Sciences, University of Rostock, Albert-Einstein-Str. 3, D-18051 Rostock, Germany
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Brioukhanov AL. Nonheme iron proteins as an alternative system of antioxidant defense in the cells of strictly anaerobic microorganisms: A review. APPL BIOCHEM MICRO+ 2008. [DOI: 10.1134/s0003683808040017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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14
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Riebe O, Fischer RJ, Bahl H. Desulfoferrodoxin of Clostridium acetobutylicum functions as a superoxide reductase. FEBS Lett 2007; 581:5605-10. [PMID: 18005665 DOI: 10.1016/j.febslet.2007.11.008] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2007] [Revised: 11/01/2007] [Accepted: 11/02/2007] [Indexed: 11/18/2022]
Abstract
Desulfoferrodoxin (cac2450) of Clostridium acetobutylicum was purified after overexpression in E. coli. In an in vitro assay the enzyme exhibited superoxide reductase activity with rubredoxin (cac2778) of C. acetobutylicum as the proximal electron donor. Rubredoxin was reduced by ferredoxin:NADP(+) reductase from spinach and NADPH. The superoxide anions, generated from dissolved oxygen using Xanthine and Xanthine oxidase, were reduced to hydrogen peroxide. Thus, we assume that desulfoferrodoxin is the key factor in the superoxide reductase dependent part of an alternative pathway for detoxification of reactive oxygen species in this obligate anaerobic bacterium.
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Affiliation(s)
- Oliver Riebe
- University of Rostock, Institute of Biological Sciences, Division of Microbiology, Albert-Einstein-Strasse 3, D-18051, Rostock, Germany
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Strube K, de Vries S, Cramm R. Formation of a dinitrosyl iron complex by NorA, a nitric oxide-binding di-iron protein from Ralstonia eutropha H16. J Biol Chem 2007; 282:20292-300. [PMID: 17507380 DOI: 10.1074/jbc.m702003200] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In Ralstonia eutropha H16, two genes, norA and norB, form a dicistronic operon that is controlled by the NO-responsive transcriptional regulator NorR. NorB has been identified as a membrane-bound NO reductase, but the physiological function of NorA is unknown. We found that, in a NorA deletion mutant, the promoter activity of the norAB operon was increased 3-fold, indicating that NorA attenuates activation of NorR. NorA shows limited sequence similarity to the oxygen carrier hemerythrin, which contains a di-iron center. Indeed, optical and EPR spectroscopy of purified NorA revealed the presence of a di-iron center, which binds oxygen in a similar way as hemerythrin. Diferrous NorA binds two molecules of NO maximally. Unexpectedly, binding of NO to the diferrous NorA required an external reductant. Two different NorA-NO species could be resolved. A minor species (up to 20%) showed an S = (1/2) EPR signal with g( perpendicular) = 2.041, and g( parallel) = 2.018, typical of a paramagnetic dinitrosyl iron complex. The major species was EPR-silent, showing characteristic signals at 420 nm and 750 nm in the optical spectrum. This species is proposed to represent a novel dinitrosyl iron complex of the form Fe(2+)-[NO](2)(2-), i.e. NO is bound as NO(-). The NO binding capacity of NorA in conjunction with its high cytoplasmic concentration (20 mum) suggests that NorA regulates transcription by lowering the free cytoplasmic concentration of NO.
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Affiliation(s)
- Katja Strube
- Institut für Biologie/Mikrobiologie, Humboldt-Universität zu Berlin, Chausseestrasse 117, 10115 Berlin, Germany
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Hindupur A, Liu D, Zhao Y, Bellamy HD, White MA, Fox RO. The crystal structure of the E. coli stress protein YciF. Protein Sci 2006; 15:2605-11. [PMID: 17001035 PMCID: PMC2242421 DOI: 10.1110/ps.062307706] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
YciF is a protein that is up-regulated when bacteria experience stress conditions, and is highly conserved in a range of bacterial species. YciF has no known structure or biochemical function. To learn more about its potential molecular function and its role in the bacterial stress response, we solved the crystal structure of YciF at 2.0 Angstrom resolution by the multiple wavelength anomalous diffraction (MAD) technique. YciF is a dimer in solution, and forms a homodimer in the crystal asymmetric unit. The two monomers form a dimer with a molecular twofold axis, with a significant burial of solvent-accessible surface area. The protein is an all-alpha protein composed of five helices: a four-helix bundle, and a short additional helix at the dimer interface. The protein is structurally similar to portions of the diiron-containing proteins, rubrerythrin and the Bacillus anthracis Dlp-2.
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Affiliation(s)
- Aditya Hindupur
- Department of Biochemistry and Molecular Biology, The University of Texas Medical Branch, Galveston, Texas 77555-0647, USA
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18
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Kurtz DM. Avoiding high-valent iron intermediates: superoxide reductase and rubrerythrin. J Inorg Biochem 2006; 100:679-93. [PMID: 16504301 DOI: 10.1016/j.jinorgbio.2005.12.017] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2005] [Accepted: 12/13/2005] [Indexed: 10/25/2022]
Abstract
The Fenton or Fenton-type reaction between aqueous ferrous ion and hydrogen peroxide generates a highly oxidizing species, most often formulated as hydroxyl radical or ferryl ([Fe(IV)O](2+)). Intracellular Fenton-type chemistry can be lethal if not controlled. Nature has, therefore, evolved enzymes to scavenge superoxide and hydrogen peroxide, the reduced dioxygen species that initiate intracellular Fenton-type chemistry. Two such enzymes found predominantly in air-sensitive bacteria and archaea, superoxide reductase (SOR) and rubrerythrin (Rbr), functioning as a peroxidase (hydrogen peroxide reductase), contain non-heme iron. The iron coordination spheres in these enzymes contain five or six protein ligands from His and Glu residues, and, in the case of SOR, a Cys residue. SOR contains a mononuclear active site that is designed to protonate and rapidly expel peroxide generated as a product of the enzymatic reaction. The ferrous SOR reacts adventitiously but relatively slowly (several seconds to a few minutes) with exogenous hydrogen peroxide, presumably in a Fenton-type reaction. The diferrous active site of Rbr reacts more rapidly with hydrogen peroxide but can divert Fenton-type reactions towards the two-electron reduction of hydrogen peroxide to water. Proximal aromatic residues may function as radical sinks for Fenton-generated oxidants. Fenton-initiated damage to these iron active sites may become apparent only under extremely oxidizing intracellular conditions.
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Affiliation(s)
- Donald M Kurtz
- Department of Chemistry and Center for Metalloenzyme Studies, University of Georgia, Athens, GA 30602, USA.
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19
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Karlsen OA, Ramsevik L, Bruseth LJ, Larsen Ø, Brenner A, Berven FS, Jensen HB, Lillehaug JR. Characterization of a prokaryotic haemerythrin from the methanotrophic bacterium Methylococcus capsulatus (Bath). FEBS J 2005; 272:2428-40. [PMID: 15885093 DOI: 10.1111/j.1742-4658.2005.04663.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
For a long time, the haemerythrin family of proteins was considered to be restricted to only a few phyla of marine invertebrates. When analysing differential protein expression in the methane-oxidizing bacterium, Methylococcus capsulatus (Bath), grown at a high and low copper-to-biomass ratio, respectively, we identified a putative prokaryotic haemerythrin expressed in high-copper cultures. Haemerythrins are recognized by a conserved sequence motif that provides five histidines and two carboxylate ligands which coordinate two iron atoms. The diiron site is located in a hydrophobic pocket and is capable of binding O(2). We cloned the M. capsulatus haemerythrin gene and expressed it in Escherichia coli as a fusion protein with NusA. The haemerythrin protein was purified to homogeneity cleaved from its fusion partner. Recombinant M. capsulatus haemerythrin (McHr) was found to fold into a stable protein. Sequence similarity analysis identified all the candidate residues involved in the binding of diiron (His22, His58, Glu62, His77, His81, His117, Asp122) and the amino acids forming the hydrophobic pocket in which O(2) may bind (Ile25, Phe59, Trp113, Leu114, Ile118). We were also able to model a three-dimensional structure of McHr maintaining the correct positioning of these residues. Furthermore, UV/vis spectrophotometric analysis demonstrated the presence of conjugated diiron atoms in McHr. A comprehensive genomic database search revealed 21 different prokaryotes containing the haemerythrin signature (PROSITE 00550), indicating that these putative haemerythrins may be a conserved prokaryotic subfamily.
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Affiliation(s)
- Odd A Karlsen
- Department of Molecular Biology, University of Bergen, Norway.
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20
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Iyer RB, Silaghi-Dumitrescu R, Kurtz DM, Lanzilotta WN. High-resolution crystal structures of Desulfovibrio vulgaris (Hildenborough) nigerythrin: facile, redox-dependent iron movement, domain interface variability, and peroxidase activity in the rubrerythrins. J Biol Inorg Chem 2005; 10:407-16. [PMID: 15895271 DOI: 10.1007/s00775-005-0650-8] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2005] [Accepted: 04/13/2005] [Indexed: 10/25/2022]
Abstract
High-resolution crystal structures of Desulfovibrio vulgaris nigerythrin (DvNgr), a member of the rubrerythrin (Rbr) family, demonstrate an approximately 2-A movement of one iron (Fe1) of the diiron site from a carboxylate to a histidine ligand upon conversion of the mixed-valent ([Fe2(II),Fe1(III)]) to diferrous states, even at cryogenic temperatures. This Glu<-->His ligand "toggling" of one iron, which also occurs in DvRbr, thus, appears to be a characteristic feature of Rbr-type diiron sites. Unique features of DvNgr revealed by these structures include redox-induced flipping of a peptide carbonyl that reversibly forms a hydrogen bond to the histidine ligand to Fe1 of the diiron site, an intra-subunit proximal orientation of the rubredoxin-(Rub)-like and diiron domains, and an electron transfer pathway consisting of six covalent and two hydrogen bonds connecting the Rub-like iron with Fe2 of the diiron site. This pathway can account for DvNgr's relatively rapid peroxidase turnover. The characteristic combination of iron sites together with the redox-dependent iron toggling between protein ligands can account for the selectivity of Rbrs for hydrogen peroxide over dioxygen.
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Affiliation(s)
- Ramesh B Iyer
- Department of Chemistry, University of Georgia, Athens, GA 30602, USA
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21
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Jin S, Kurtz DM, Liu ZJ, Rose J, Wang BC. Displacement of iron by zinc at the diiron site of Desulfovibrio vulgaris rubrerythrin: X-ray crystal structure and anomalous scattering analysis. J Inorg Biochem 2005; 98:786-96. [PMID: 15134924 DOI: 10.1016/j.jinorgbio.2004.01.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2003] [Revised: 01/09/2004] [Accepted: 01/15/2004] [Indexed: 10/26/2022]
Abstract
X-ray crystal structures of recombinant Desulfovibrio (D.) vulgaris rubrerythrin (Rbr) have shown a diiron site, whereas the crystal structure of Rbr "as-isolated" from D. vulgaris was reported to contain a mixed Zn,Fe binuclear site. To investigate the possibility that zinc had displaced iron during isolation or crystallization of the "as-isolated" D. vulgaris Rbr, the X-ray crystal structure of recombinant D. vulgaris all-iron Rbr that had been incubated with excess zinc sulfate prior to crystallization, yielding a protein labeled Zn,FeRbr, was solved. Analysis of the anomalous scattering data obtained at two different wavelengths showed that zinc had displaced a significant proportion of iron from both iron centers of the diiron site, and that no iron had been displaced from the [Fe(SCys)(4)] site. UV-visible absorption spectra of the redissolved Zn,FeRbr crystals showed 30-40% retention of oxo-bridged diferric sites, and the redissolved crystals had 37% of the peroxidase specific activity of the starting all-iron Rbr, which, together with the crystallographic results, indicate a predominant mixture of Fe1,Fe2 and Zn1,Zn2 sites. The structure of the Zn(Fe)1,Fe(Zn)2 binuclear site in the Zn,FeRbr crystals was very similar to that of the Zn,Fe binuclear site reported for the "as-isolated" D. vulgaris Rbr, including tetrahedral four-coordination at the Zn(Fe)1 site. The diiron sites in the recombinant Zn,FeRbr crystals were likely at least partially reduced during synchrotron irradiation. Our results suggest that the mixed-metal binuclear site reported for the "as-isolated" D. vulgaris Rbr could be due to displacement of iron from a native diiron site by adventitious zinc during isolation and/or crystallization, and that reduced diiron and dizinc sites can adopt very similar structures in Rbr.
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Affiliation(s)
- Shi Jin
- Department of Chemistry, Center for Metalloenzyme Studies, University of Georgia, Athens, GA 30602, USA
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22
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Weinberg MV, Jenney FE, Cui X, Adams MWW. Rubrerythrin from the hyperthermophilic archaeon Pyrococcus furiosus is a rubredoxin-dependent, iron-containing peroxidase. J Bacteriol 2004; 186:7888-95. [PMID: 15547260 PMCID: PMC529063 DOI: 10.1128/jb.186.23.7888-7895.2004] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Rubrerythrin was purified by multistep chromatography under anaerobic, reducing conditions from the hyperthermophilic archaeon Pyrococcus furiosus. It is a homodimer with a molecular mass of 39.2 kDa and contains 2.9 +/- 0.2 iron atoms per subunit. The purified protein had peroxidase activity at 85 degrees C using hydrogen peroxide with reduced P. furiosus rubredoxin as the electron donor. The specific activity was 36 micromol of rubredoxin oxidized/min/mg with apparent K(m) values of 35 and 70 microM for hydrogen peroxide and rubredoxin, respectively. When rubrerythrin was combined with rubredoxin and P. furiosus NADH:rubredoxin oxidoreductase, the complete system used NADH as the electron donor to reduce hydrogen peroxide with a specific activity of 7.0 micromol of H(2)O(2) reduced/min/mg of rubrerythrin at 85 degrees C. Strangely, as-purified (reduced) rubrerythrin precipitated when oxidized by either hydrogen peroxide, air, or ferricyanide. The gene (PF1283) encoding rubrerythrin was expressed in Escherichia coli grown in medium with various metal contents. The purified recombinant proteins each contained approximately three metal atoms/subunit, ranging from 0.4 Fe plus 2.2 Zn to 1.9 Fe plus 1.2 Zn, where the metal content of the protein depended on the metal content of the E. coli growth medium. The peroxidase activities of the recombinant forms were proportional to the iron content. P. furiosus rubrerythrin is the first to be characterized from a hyperthermophile or from an archaeon, and the results are the first demonstration that this protein functions in an NADH-dependent, hydrogen peroxide:rubredoxin oxidoreductase system. Rubrerythrin is proposed to play a role in the recently defined anaerobic detoxification pathway for reactive oxygen species.
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Affiliation(s)
- Michael V Weinberg
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602-7229, USA
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23
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Sazinsky MH, Bard J, Di Donato A, Lippard SJ. Crystal structure of the toluene/o-xylene monooxygenase hydroxylase from Pseudomonas stutzeri OX1. Insight into the substrate specificity, substrate channeling, and active site tuning of multicomponent monooxygenases. J Biol Chem 2004; 279:30600-10. [PMID: 15096510 DOI: 10.1074/jbc.m400710200] [Citation(s) in RCA: 168] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The four-component toluene/o-xylene monooxygenase (ToMO) from Pseudomonas stutzeri OX1 is capable of oxidizing arenes, alkenes, and haloalkanes at a carboxylate-bridged diiron center similar to that of soluble methane monooxygenase (sMMO). The remarkable variety of substrates accommodated by ToMO invites applications ranging from bioremediation to the regio- and enantiospecific oxidation of hydrocarbons on an industrial scale. We report here the crystal structures of the ToMO hydroxylase (ToMOH), azido ToMOH, and ToMOH containing the product analogue 4-bromophenol to 2.3 A or greater resolution. The catalytic diiron(III) core resembles that of the sMMO hydroxylase, but aspects of the alpha2beta2gamma2 tertiary structure are notably different. Of particular interest is a 6-10 A-wide channel of approximately 35 A in length extending from the active site to the protein surface. The presence of three bromophenol molecules in this space confirms this route as a pathway for substrate entrance and product egress. An analysis of the ToMOH active site cavity offers insights into the different substrate specificities of multicomponent monooxygenases and explains the behavior of mutant forms of homologous enzymes described in the literature.
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Affiliation(s)
- Matthew H Sazinsky
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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Wakagi T. Sulerythrin, the smallest member of the rubrerythrin family, from a strictly aerobic and thermoacidophilic archaeon, Sulfolobus tokodaii strain 7. FEMS Microbiol Lett 2003; 222:33-7. [PMID: 12757943 DOI: 10.1016/s0378-1097(03)00233-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
A protein corresponding to the N-terminal domain of rubrerythrin was isolated from a strictly aerobic archaeon, Sulfolobus tokodaii strain 7. The molecular mass was found to be 15.8 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, 16278 Da by time-of-flight mass spectrometry and 34.5 kDa by gel filtration chromatography, suggesting that the protein is dimeric. Two mol iron and 1-2 mol zinc mol(-1) protein were detected. On addition of the azide ion, the absorption spectrum was greatly affected. The far UV circular dichroism spectrum suggested that the protein was mostly composed of alpha-helices. The N-terminal sequence completely matched the open reading frame, st2370, recently found on genome analysis of the organism. The protein was homologous to rubrerythrin but lacked a C-terminal rubredoxin domain. It was found in the genus Sulfolobus and therefore named sulerythrin; it is the smallest and first aerobic member of the rubrerythrin family.
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Affiliation(s)
- Takayoshi Wakagi
- Department of Biotechnology, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan.
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25
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Niu S, Wang XB, Nichols JA, Wang LS, Ichiye T. Combined Quantum Chemistry and Photoelectron Spectroscopy Study of the Electronic Structure and Reduction Potentials of Rubredoxin Redox Site Analogues. J Phys Chem A 2003. [DOI: 10.1021/jp034316f] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Shuqiang Niu
- School of Molecular Biosciences, Washington State University, Pullman, Washington 99164-4660, Department of Physics, Washington State University, 2710 University Drive, Richland, Washington 99352, and W. R. Wiley Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352
| | - Xue-Bin Wang
- School of Molecular Biosciences, Washington State University, Pullman, Washington 99164-4660, Department of Physics, Washington State University, 2710 University Drive, Richland, Washington 99352, and W. R. Wiley Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352
| | - Jeffrey A. Nichols
- School of Molecular Biosciences, Washington State University, Pullman, Washington 99164-4660, Department of Physics, Washington State University, 2710 University Drive, Richland, Washington 99352, and W. R. Wiley Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352
| | - Lai-Sheng Wang
- School of Molecular Biosciences, Washington State University, Pullman, Washington 99164-4660, Department of Physics, Washington State University, 2710 University Drive, Richland, Washington 99352, and W. R. Wiley Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352
| | - Toshiko Ichiye
- School of Molecular Biosciences, Washington State University, Pullman, Washington 99164-4660, Department of Physics, Washington State University, 2710 University Drive, Richland, Washington 99352, and W. R. Wiley Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352
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26
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Jin S, Kurtz DM, Liu ZJ, Rose J, Wang BC. X-ray crystal structures of reduced rubrerythrin and its azide adduct: a structure-based mechanism for a non-heme diiron peroxidase. J Am Chem Soc 2002; 124:9845-55. [PMID: 12175244 DOI: 10.1021/ja026587u] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Rubrerythrin (Rbr) is a 44-kDa homodimeric protein, found in many air-sensitive bacteria and archaea, which contains a unique combination of a rubredoxin-like [Fe(SCys)(4)] site and a non-sulfur, oxo/dicarboxylato-bridged diiron site. The diiron site structure resembles those found in O2-activating diiron enzymes. However, Rbr instead appears to function as a hydrogen peroxide reductase (peroxidase). The diferrous site in all-ferrous Rbr (Rbr(red)) shows a much greater reactivity with H2O2 than does the diferric site in all-ferric Rbr (Rbr(ox)), but only the latter structure has been reported. Here we report the X-ray crystal structures of the recombinant Rbr(red) from the sulfate reducing bacterium, Desulfovibrio vulgaris, as well as its azide adduct (Rbr(red)N3). We have also redetermined the structure of Rbr(ox) to a higher resolution than previously reported. The structural differences between Rbr(ox) and Rbr(red) are localized entirely at the diiron site. The most striking structural change upon reduction of the diferric to the diferrous site of Rbr is a 1.8-A movement of one iron away from a unique glutamate carboxylate ligand and toward a trans-disposed histidine side chain, which replaces the glutamate as a ligand. This movement increases the inter-iron distance from 3.3 to 4 A. Rbr(red)N(3) shows this same iron movement and His-->Glu ligand replacement relative to Rbr(ox), and, in addition, an azide coordinated to the diiron site in a cis mu-1,3 fashion, replacing two solvent ligands in Rbr(red). Relative to those in O2-activating enzymes, the bridging carboxylate ligation of the Rbr diiron site is less flexible upon diferric/diferrous interconversion. The diferrous site is also much more rigid, symmetrical, and solvent-exposed than those in O2-activating enzymes. On the basis of these unique structural features, a mechanism is proposed for facile reduction of hydrogen peroxide by Rbr involving a cis mu-eta(2) H2O2 diferrous intermediate.
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Affiliation(s)
- Shi Jin
- Department of Chemistry and Biochemistry, Center for Metalloenzyme Studies and Georgia X-ray Crystallography Center, University of Georgia, Athens, Georgia 30602, USA
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Coulter ED, Kurtz DM. A role for rubredoxin in oxidative stress protection in Desulfovibrio vulgaris: catalytic electron transfer to rubrerythrin and two-iron superoxide reductase. Arch Biochem Biophys 2001; 394:76-86. [PMID: 11566030 DOI: 10.1006/abbi.2001.2531] [Citation(s) in RCA: 110] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Desulfovibrio vulgaris rubredoxin, which contains a single [Fe(SCys)4] site, is shown to be a catalytically competent electron donor to two enzymes from the same organism, namely, rubrerythrin and two-iron superoxide reductase (a.k.a. rubredoxin oxidoreductase or desulfoferrodoxin). These two enzymes have been implicated in catalytic reduction of hydrogen peroxide and superoxide, respectively, during periods of oxidative stress in D. vulgaris, but their proximal electron donors had not been characterized. We further demonstrate the incorrectness of a previous report that rubredoxin is not an electron donor to the superoxide reductase and describe convenient assays for demonstrating the catalytic competence of all three proteins in their respective functions. Rubrerythrin is shown to be an efficient rubredoxin peroxidase in which the rubedoxin:hydrogen peroxide redox stoichiometry is 2:1 mol:mol. Using spinach ferredoxin-NADP+ oxidoreductase (FNR) as an artificial, but proficient, NADPH:rubredoxin reductase, rubredoxin was further found to catalyze rapid and complete reduction of all Fe3+ to Fe2+ in rubrerythrin by NADPH under anaerobic conditions. The combined system, FNR/rubredoxin/rubrerythrin, was shown to function as a catalytically competent NADPH peroxidase. Another small rubredoxin-like D. vulgaris protein, Rdl, could not substitute for rubredoxin as a peroxidase substrate of rubrerythrin. Similarly, D. vulgaris rubredoxin was demonstrated to efficiently catalyze reduction of D. vulgaris two-iron superoxide reductase and, when combined with FNR, to function as an NADPH:superoxide oxidoreductase. We suggest that, during periods of oxidative stress, rubredoxin could divert electron flow from the electron transport chain of D. vulgaris to rubrerythrin and superoxide reductase, thereby simultaneously protecting autoxidizable redox enzymes and lowering intracellular hydrogen peroxide and superoxide levels.
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Affiliation(s)
- E D Coulter
- Department of Chemistry, University of Georgia, Athens, Georgia 30602, USA
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Das A, Coulter ED, Kurtz DM, Ljungdahl LG. Five-gene cluster in Clostridium thermoaceticum consisting of two divergent operons encoding rubredoxin oxidoreductase- rubredoxin and rubrerythrin-type A flavoprotein- high-molecular-weight rubredoxin. J Bacteriol 2001; 183:1560-7. [PMID: 11160086 PMCID: PMC95040 DOI: 10.1128/jb.183.5.1560-1567.2001] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A five-gene cluster encoding four nonheme iron proteins and a flavoprotein from the thermophilic anaerobic bacterium Clostridium thermoaceticum (Moorella thermoacetica) was cloned and sequenced. Based on analysis of deduced amino acid sequences, the genes were identified as rub (rubredoxin), rbo (rubredoxin oxidoreductase), rbr (rubrerythrin), fprA (type A flavoprotein), and a gene referred to as hrb (high-molecular-weight rubredoxin). Northern blot analysis demonstrated that the five-gene cluster is organized as two subclusters, consisting of two divergently transcribed operons, rbr-fprA-hrb and rbo-rub. The rbr, fprA, and rub genes were expressed in Escherichia coli, and their encoded recombinant proteins were purified. The molecular masses, UV-visible absorption spectra, and cofactor contents of the recombinant rubrerythrin, rubredoxin, and type A flavoprotein were similar to those of respective homologs from other microorganisms. Antibodies raised against Desulfovibrio vulgaris Rbr reacted with both native and recombinant Rbr from C. thermoaceticum, indicating that this protein was expressed in the native organism. Since Rbr and Rbo have been recently implicated in oxidative stress protection in several anaerobic bacteria and archaea, we suggest a similar function of these proteins in oxygen tolerance of C. thermoaceticum.
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Affiliation(s)
- A Das
- Center for Biological Resource Recovery and Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602-7229, USA
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29
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Lumppio HL, Shenvi NV, Summers AO, Voordouw G, Kurtz DM. Rubrerythrin and rubredoxin oxidoreductase in Desulfovibrio vulgaris: a novel oxidative stress protection system. J Bacteriol 2001; 183:101-8. [PMID: 11114906 PMCID: PMC94855 DOI: 10.1128/jb.183.1.101-108.2001] [Citation(s) in RCA: 159] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2000] [Accepted: 10/11/2000] [Indexed: 11/20/2022] Open
Abstract
Evidence is presented for an alternative to the superoxide dismutase (SOD)-catalase oxidative stress defense system in Desulfovibrio vulgaris (strain Hildenborough). This alternative system consists of the nonheme iron proteins, rubrerythrin (Rbr) and rubredoxin oxidoreductase (Rbo), the product of the rbo gene (also called desulfoferrodoxin). A Deltarbo strain of D. vulgaris was found to be more sensitive to internal superoxide exposure than was the wild type. Unlike Rbo, expression of plasmid-borne Rbr failed to restore the aerobic growth of a SOD-deficient strain of Escherichia coli. Conversely, plasmid-borne expression of two different Rbrs from D. vulgaris increased the viability of a catalase-deficient strain of E. coli that had been exposed to hydrogen peroxide whereas Rbo actually decreased the viability. A previously undescribed D. vulgaris gene was found to encode a protein having 50% sequence identity to that of E. coli Fe-SOD. This gene also encoded an extended N-terminal sequence with high homologies to export signal peptides of periplasmic redox proteins. The SOD activity of D. vulgaris is not affected by the absence of Rbo and is concentrated in the periplasmic fraction of cell extracts. These results are consistent with a superoxide reductase rather than SOD activity of Rbo and with a peroxidase activity of Rbr. A joint role for Rbo and Rbr as a novel cytoplasmic oxidative stress protection system in D. vulgaris and other anaerobic microorganisms is proposed.
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Affiliation(s)
- H L Lumppio
- Department of Microbiology, University of Georgia, Athens, Georgia 30602, USA
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31
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Abstract
P. S. Alban et al. (J. Appl. Microbiol. (1998) 85, 875-882) reported that a mutant H2O2-resistant strain of Spirullum (S.) volutans showed constitutive overexpression of a protein whose amino acid sequence and molecular weight closely resembled that of a subunit of rubrerythrin, a non-heme iron protein with no known function. They also reported that the mutant strain, but not the wild-type, showed NADH peroxidase activity. Here we demonstrate that rubrerythrin and nigerythrin from Desulfovibrio vulgaris and rubrerythrin from Clostridium perfringens show NADH peroxidase activities in an in vitro system containing NADH, hydrogen peroxide, and a bacterial NADH oxidoreductase. The peroxidase specific activities of the rubrerythrins with the "classical" heme peroxidase substrate, o-dianisidine, are many orders of magnitude lower than that of horseradish peroxidase. These results are consistent with the phenotype of the H2O2-resistant strain of S. volutans. The reaction of reduced (i.e., all-ferrous) rubrerythrin with excess O2 takes several minutes, whereas the anaerobic reaction of reduced rubrerythrin with hydrogen peroxide is on the millisecond time scale and results in full oxidation of all iron centers to their ferric states. Rubrerythrins could, thus, function as the terminal components of NADH peroxidases in air-sensitive bacteria and archaea.
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Affiliation(s)
- E D Coulter
- Department of Chemistry, Center for Metalloenzyme Studies, University of Georgia, Athens 30602, USA
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32
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Lei QP, Cui X, Kurtz DM, Amster IJ, Chernushevich IV, Standing KG. Electrospray mass spectrometry studies of non-heme iron-containing proteins. Anal Chem 1998; 70:1838-46. [PMID: 9599583 DOI: 10.1021/ac971181z] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The oligomeric state and the metal atom stoichiometry of a series of non-heme iron-containing, multimeric proteins have been measured using electrospray ionization (ESI) in a time-of-flight (TOF) mass spectrometer. The proteins were obtained both from natural sources and by overexpression of recombinant DNA in Escherichia coli. ESI-TOF mass spectra of the metalloproteins present in nondenaturing solutions exhibit peaks corresponding to the multimeric forms of the holoproteins containing the expected number of metal atoms. Capillary-skimmer dissociation of the holoproteins produces a series of ions, which allows an exact count of the number of metal atoms present in each subunit, and also provides an indication of the oxidation state of the metal atoms. Two recombinant proteins, Phascolopsis gouldii hemerythrin (Pg-Hr) and Desulfovibrio vulgaris rubrerythrin (Dv-Rr), have been examined as well as hemerythrin isolated from Lingula reevii (Lr-Hr). ESI-TOF measurements of the aqueous solution of Pg-Hr at pH 6 yields ions of mass 108,783 Da, in close agreement with the calculated average molecular mass of an intact octameric holoprotein. Capillary-skimmer dissociation of the ions of the holoprotein produces a mass spectrum that contains peaks corresponding to a low m/z monomer and a high m/z heptamer. The masses of the monomer ions produced in this manner are assigned to the aposubunit, [subunit + Fe - 3H]+, and [subunit + 2Fe - 6 H]+. Naturally occurring Lr-Hr is composed of two subunits with average molecular masses measured under denaturing conditions by ESI-TOF to be 13,877.0 Da for the alpha-subunit and 13,517.5 Da for the beta-subunit. Under nondenaturing conditions, a multimeric species with a molecular weight of 110,663 Da is measured by ESI-TOF, corresponding to an alpha 4 beta 4 octamer. Capillary-skimmer dissociation of the alpha 4 beta 4 oligomer produces ions corresponding to both types of monomers (alpha and beta) and the corresponding heptamers (alpha 3 beta 4 and alpha 4 beta 3). In ESI-TOF measurements of recombinant rubrerythrin Dv-Rr using nondenaturing conditions, the principal ion observed corresponds to a homotetramer with an average molecular mass of 86,844 Da. Capillary-skimmer dissociation of the rubrerythrin tetramer leads to formation of a series of peaks corresponding to the subunit of the apoprotein and to subunits containing from one to three specifically bound iron atoms.
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Affiliation(s)
- Q P Lei
- Department of Chemistry, University of Georgia, Athens 30602, USA
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Re-engineering the diiron site in rubrerythrin towards that in ribonucleotide reductase. Inorganica Chim Acta 1997. [DOI: 10.1016/s0020-1693(97)05662-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Lumppio HL, Shenvi NV, Garg RP, Summers AO, Kurtz DM. A rubrerythrin operon and nigerythrin gene in Desulfovibrio vulgaris (Hildenborough). J Bacteriol 1997; 179:4607-15. [PMID: 9226272 PMCID: PMC179298 DOI: 10.1128/jb.179.14.4607-4615.1997] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Rubrerythrin is a nonheme iron protein of unknown function isolated from Desulfovibrio vulgaris (Hildenborough). We have sequenced a 3.3-kbp Sal1 fragment of D. vulgaris chromosomal DNA containing the rubrerythrin gene, rbr, identified additional open reading frames (ORFs) adjacent to rbr, and shown that these ORFs are part of a transcriptional unit containing rbr. One ORF, designated fur, lies just upstream of rbr and encodes a 128-amino-acid-residue protein which shows homology to Fur (ferric uptake regulatory) proteins from other purple bacteria. The other ORF, designated rdl, lies just downstream of rbr and encodes a 74-residue protein with significant sequence homology to rubredoxins but with a different number and spacing of cysteine residues. Overexpression of rdl in Escherichia coli yielded a protein, Rdl, which has spectroscopic properties and iron content consistent with one Fe3+(SCys)4 site per polypeptide but is clearly distinct from both rubrerythrin and a related protein, nigerythrin. Northern analysis indicated that fur, rbr, and rdl were each present on a transcript of 1.3 kb; i.e., these three genes are cotranscribed. Because D. vulgaris nigerythrin appears to be closely related to rubrerythrin, and its function is also unknown, we cloned and sequenced the gene encoding nigerythrin, ngr. The amino acid sequence of nigerythrin is 33% identical to that of rubrerythrin, and all residues which furnish iron ligands to both the FeS4 and diiron-oxo sites in rubrerythrin are conserved in nigerythrin. Despite the close resemblance of these two proteins, ngr was found to be no closer than 7 kb to rbr on the D. vulgaris chromosome, and Northern analysis showed that, in contrast to rbr, ngr is not cotranscribed with other genes. Possible redox-linked functions for rubrerythrin and nigerythrin in iron homeostasis are proposed.
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Affiliation(s)
- H L Lumppio
- Department of Microbiology and Center for Metalloenzyme Studies, University of Georgia, Athens 30602, USA
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Shanklin J, Achim C, Schmidt H, Fox BG, Münck E. Mössbauer studies of alkane omega-hydroxylase: evidence for a diiron cluster in an integral-membrane enzyme. Proc Natl Acad Sci U S A 1997; 94:2981-6. [PMID: 9096332 PMCID: PMC20308 DOI: 10.1073/pnas.94.7.2981] [Citation(s) in RCA: 164] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/1996] [Accepted: 01/18/1997] [Indexed: 02/04/2023] Open
Abstract
The gene encoding the alkane omega-hydroxylase (AlkB; EC 1.14.15.3) from Pseudomonas oleovorans was expressed in Escherichia coli. The integral-membrane protein was purified as nearly homogeneous protein vesicles by differential ultracentrifugation and HPLC cation exchange chromatography without the detergent solubilization normally required for membrane proteins. Purified AlkB had specific activity of up to 5 units/mg for octane-dependent NADPH consumption. Mössbauer studies of AlkB showed that it contains an exchange-coupled dinuclear iron cluster of the type found in soluble diiron proteins such as hemerythrin, ribonucleotide reductase, methane monooxygenase, stearoyl-acyl carrier protein (ACP) delta9 desaturase, rubrerythrin, and purple acid phosphatase. In the as-isolated enzyme, the cluster contains an antiferromagnetically coupled pair of high-spin Fe(III) sites, with an occupancy of up to 0.9 cluster per AlkB. The diferric cluster could be reduced by sodium dithionite, and the diferrous state was found to be stable in air. When both O2 and substrate (octane) were added, however, the diferrous cluster was quantitatively reoxidized, proving that the diiron cluster occupies the active site. Mossbauer data on reduced AlkB are consistent with a cluster coordination rich in nitrogen-containing ligands. New sequence analyses indicate that at least 11 nonheme integral-membrane enzymes, including AlkB, contain the 8-histidine motif required for catalytic activity in stearoyl-CoA desaturase. Based on our Mössbauer studies of AlkB, we propose that the integral-membrane enzymes in this family contain diiron clusters. Because these enzymes catalyze a diverse range of oxygenation reactions, this proposal suggests a greatly expanded role for diiron clusters in O2-activation biochemistry.
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Affiliation(s)
- J Shanklin
- Department of Biology, Brookhaven National Laboratory, Upton, NY 11973, USA
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Sturgeon BE, Doan PE, Liu KE, Burdi D, Tong WH, Nocek JM, Gupta N, Stubbe J, Kurtz, DM, Lippard SJ, Hoffman BM. Non-Kramers ESEEM of Integer-Spin Diferrous Carboxylate-Bridged Clusters in Proteins. J Am Chem Soc 1997. [DOI: 10.1021/ja9628157] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Bradley E. Sturgeon
- Contribution from the Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, and Department of Chemistry and Center for Metalloenzyme Studies, University of Georgia, Athens, Georgia 30602-2556
| | - Peter E. Doan
- Contribution from the Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, and Department of Chemistry and Center for Metalloenzyme Studies, University of Georgia, Athens, Georgia 30602-2556
| | - Katherine E. Liu
- Contribution from the Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, and Department of Chemistry and Center for Metalloenzyme Studies, University of Georgia, Athens, Georgia 30602-2556
| | - Doug Burdi
- Contribution from the Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, and Department of Chemistry and Center for Metalloenzyme Studies, University of Georgia, Athens, Georgia 30602-2556
| | - Wing H. Tong
- Contribution from the Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, and Department of Chemistry and Center for Metalloenzyme Studies, University of Georgia, Athens, Georgia 30602-2556
| | - Judith M. Nocek
- Contribution from the Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, and Department of Chemistry and Center for Metalloenzyme Studies, University of Georgia, Athens, Georgia 30602-2556
| | - Nishi Gupta
- Contribution from the Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, and Department of Chemistry and Center for Metalloenzyme Studies, University of Georgia, Athens, Georgia 30602-2556
| | - JoAnne Stubbe
- Contribution from the Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, and Department of Chemistry and Center for Metalloenzyme Studies, University of Georgia, Athens, Georgia 30602-2556
| | - Donald M. Kurtz,
- Contribution from the Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, and Department of Chemistry and Center for Metalloenzyme Studies, University of Georgia, Athens, Georgia 30602-2556
| | - Stephen J. Lippard
- Contribution from the Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, and Department of Chemistry and Center for Metalloenzyme Studies, University of Georgia, Athens, Georgia 30602-2556
| | - Brian M. Hoffman
- Contribution from the Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, and Department of Chemistry and Center for Metalloenzyme Studies, University of Georgia, Athens, Georgia 30602-2556
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Herold S, Lippard SJ. Carboxylate-Bridged Diiron(II) Complexes: Synthesis, Characterization, and O2-Reactivity of Models for the Reduced Diiron Centers in Methane Monooxygenase and Ribonucleotide Reductase. J Am Chem Soc 1997. [DOI: 10.1021/ja9628563] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Susanna Herold
- Contribution from the Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Stephen J. Lippard
- Contribution from the Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
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Lehmann Y, Meile L, Teuber M. Rubrerythrin from Clostridium perfringens: cloning of the gene, purification of the protein, and characterization of its superoxide dismutase function. J Bacteriol 1996; 178:7152-8. [PMID: 8955396 PMCID: PMC178627 DOI: 10.1128/jb.178.24.7152-7158.1996] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The food-borne pathogen Clostridium perfringens, which is an obligate anaerobe, showed growth under conditions of oxidative stress. In protein extracts we looked for superoxide dismutase (SOD) activities which might scavenge highly toxic superoxide radicals evolving under such stress conditions. Using the classical assay to detect SOD activity on gels after electrophoresis of C. perfringens proteins, we obtained a pattern of three major bands indicating SOD activity. The protein representing the brightest band was purified by three chromatographic steps. On the basis of 20 amino acids determined from the N terminus of the protein, we designed a degenerate oligonucleotide probe to isolate the corresponding gene. We finally sequenced an open reading frame of 195 amino acids (molecular mass, 21,159 Da) with a strong homology to the Desulfovibrio vulgaris rubrerythrin; therefore, we assumed to have cloned a rubrerythrin gene from C. perfringens, and we named it rbr. The C-terminal region of the newly detected rubrerythrin from C. perfringens contains a characteristic non-heme, non-sulfur iron-binding site -Cys-X-X-Cys-(X)12-Cys-X-X-Cys- similar to that found in rubrerythrin from D. vulgaris. In addition, three -Glu-X-X-His- sequences could represent diiron binding domains. We observed SOD activity in extracts of Escherichia coli strains containing the recombinant rbr gene from C. perfringens. A biological function of rubrerythrin as SOD was confirmed with the functional complementation by the rbr gene of an E. coli mutant strain lacking SOD activity. We therefore suppose that rubrerythrin plays a role as a scavenger of oxygen radicals.
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Affiliation(s)
- Y Lehmann
- Laboratorium für Lebensmittel-Mikrobiologie, Institut für Lebensmittelwissenschaften, Eidgenössische Technische Hochschule, ETH-Zentrum, Zürich, Switzerland
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deMaré F, Kurtz DM, Nordlund P. The structure of Desulfovibrio vulgaris rubrerythrin reveals a unique combination of rubredoxin-like FeS4 and ferritin-like diiron domains. NATURE STRUCTURAL BIOLOGY 1996; 3:539-46. [PMID: 8646540 DOI: 10.1038/nsb0696-539] [Citation(s) in RCA: 112] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
We have determined the structure of rubrerythrin, a non-haem iron protein from the anaerobic sulphate-reducing bacterium, Desulfovibrio vulgaris (Hildenborough), by X-ray crystallography. The structure reveals a tetramer of two-domain subunits. Each subunit contains a four-helix bundle surrounding a diiron-oxo site and a C-terminal rubredoxin-like FeS4 domain. The diiron-oxo site contains a larger number of carboxylate ligands and a higher degree of solvent exposure than do those in other diiron-oxo proteins. The four-helix bundle of rubrerythrin closely resembles those of the ferritin and bacterioferritin subunits, suggesting a relationship among these proteins-consistent with the recently demonstrated ferroxidase activity of rubrerythrin.
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Affiliation(s)
- F deMaré
- Department of Molecular Biology, Stockholm University, Sweden
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40
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Protein determinants of metal site reduction potentials: site-directed mutagenesis studies of Clostridium pasteurianum rubredoxin. Inorganica Chim Acta 1996. [DOI: 10.1016/0020-1693(95)04874-x] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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41
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Lloyd SG, Franco R, Moura JJG, Moura I, Ferreira GC, Huynh BH. Functional Necessity and Physicochemical Characteristics of the [2Fe−2S] Cluster in Mammalian Ferrochelatase. J Am Chem Soc 1996. [DOI: 10.1021/ja954000o] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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