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Koebke KJ, Pinter TBJ, Pitts WC, Pecoraro VL. Catalysis and Electron Transfer in De Novo Designed Metalloproteins. Chem Rev 2022; 122:12046-12109. [PMID: 35763791 PMCID: PMC10735231 DOI: 10.1021/acs.chemrev.1c01025] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
One of the hallmark advances in our understanding of metalloprotein function is showcased in our ability to design new, non-native, catalytically active protein scaffolds. This review highlights progress and milestone achievements in the field of de novo metalloprotein design focused on reports from the past decade with special emphasis on de novo designs couched within common subfields of bioinorganic study: heme binding proteins, monometal- and dimetal-containing catalytic sites, and metal-containing electron transfer sites. Within each subfield, we highlight several of what we have identified as significant and important contributions to either our understanding of that subfield or de novo metalloprotein design as a discipline. These reports are placed in context both historically and scientifically. General suggestions for future directions that we feel will be important to advance our understanding or accelerate discovery are discussed.
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Affiliation(s)
- Karl J. Koebke
- Department of Chemistry, University of Michigan Ann Arbor, MI 48109 USA
| | | | - Winston C. Pitts
- Department of Chemistry, University of Michigan Ann Arbor, MI 48109 USA
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2
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Jeoung JH, Rünger S, Haumann M, Neumann B, Klemke F, Davis V, Fischer A, Dau H, Wollenberger U, Dobbek H. Bimetallic Mn, Fe, Co, and Ni Sites in a Four-Helix Bundle Protein: Metal Binding, Structure, and Peroxide Activation. Inorg Chem 2021; 60:17498-17508. [PMID: 34757735 DOI: 10.1021/acs.inorgchem.1c01919] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Bimetallic active sites in enzymes catalyze small-molecule conversions that are among the top 10 challenges in chemistry. As different metal cofactors are typically incorporated in varying protein scaffolds, it is demanding to disentangle the individual contributions of the metal and the protein matrix to the activity. Here, we compared the structure, properties, and hydrogen peroxide reactivity of four homobimetallic cofactors (Mn(II)2, Fe(II)2, Co(II)2, Ni(II)2) that were reconstituted into a four-helix bundle protein. Reconstituted proteins were studied in solution and in crystals. All metals bind with high affinity and yield similar cofactor structures. Cofactor variants react with H2O2 but differ in their turnover rates, accumulated oxidation states, and trapped peroxide-bound intermediates. Varying the metal composition thus creates opportunities to tune the reactivity of the bimetallic cofactor and to study and functionalize reactive species.
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Affiliation(s)
- Jae-Hun Jeoung
- Department of Biology, Strukturbiologie/Biochemie, Humboldt-Universität zu Berlin, Unter den Linden 6, 10099 Berlin, Germany
| | - Stefan Rünger
- Department of Biology, Strukturbiologie/Biochemie, Humboldt-Universität zu Berlin, Unter den Linden 6, 10099 Berlin, Germany
| | - Michael Haumann
- Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Bettina Neumann
- Institute of Biochemistry and Biology, University of Potsdam, 14476 Potsdam, Germany
| | - Friederike Klemke
- Department of Biology, Strukturbiologie/Biochemie, Humboldt-Universität zu Berlin, Unter den Linden 6, 10099 Berlin, Germany
| | - Victoria Davis
- Institute for Inorganic and Analytical Chemistry (IAAC), Albert-Ludwigs-Universität Freiburg, 79104 Freiburg, Germany.,Freiburg Material Research Center (FMF), University of Freiburg, 79104 Freiburg, Germany.,Freiburg Center for Interactive Materials and Bioinspired Technologies, University of Freiburg, 79104 Freiburg, Germany.,Cluster of Excellence livMatS@FIT─Freiburg Center for Interactive Materials and Bioinspired Technologies, University of Freiburg, 79104 Freiburg, Germany
| | - Anna Fischer
- Institute for Inorganic and Analytical Chemistry (IAAC), Albert-Ludwigs-Universität Freiburg, 79104 Freiburg, Germany.,Freiburg Material Research Center (FMF), University of Freiburg, 79104 Freiburg, Germany.,Freiburg Center for Interactive Materials and Bioinspired Technologies, University of Freiburg, 79104 Freiburg, Germany.,Cluster of Excellence livMatS@FIT─Freiburg Center for Interactive Materials and Bioinspired Technologies, University of Freiburg, 79104 Freiburg, Germany
| | - Holger Dau
- Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Ulla Wollenberger
- Institute of Biochemistry and Biology, University of Potsdam, 14476 Potsdam, Germany
| | - Holger Dobbek
- Department of Biology, Strukturbiologie/Biochemie, Humboldt-Universität zu Berlin, Unter den Linden 6, 10099 Berlin, Germany
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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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Lu CH, Lin YF, Lin JJ, Yu CS. Prediction of metal ion-binding sites in proteins using the fragment transformation method. PLoS One 2012; 7:e39252. [PMID: 22723976 PMCID: PMC3377655 DOI: 10.1371/journal.pone.0039252] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2011] [Accepted: 05/21/2012] [Indexed: 11/19/2022] Open
Abstract
The structure of a protein determines its function and its interactions with other factors. Regions of proteins that interact with ligands, substrates, and/or other proteins, tend to be conserved both in sequence and structure, and the residues involved are usually in close spatial proximity. More than 70,000 protein structures are currently found in the Protein Data Bank, and approximately one-third contain metal ions essential for function. Identifying and characterizing metal ion-binding sites experimentally is time-consuming and costly. Many computational methods have been developed to identify metal ion-binding sites, and most use only sequence information. For the work reported herein, we developed a method that uses sequence and structural information to predict the residues in metal ion-binding sites. Six types of metal ion-binding templates- those involving Ca(2+), Cu(2+), Fe(3+), Mg(2+), Mn(2+), and Zn(2+)-were constructed using the residues within 3.5 Å of the center of the metal ion. Using the fragment transformation method, we then compared known metal ion-binding sites with the templates to assess the accuracy of our method. Our method achieved an overall 94.6 % accuracy with a true positive rate of 60.5 % at a 5 % false positive rate and therefore constitutes a significant improvement in metal-binding site prediction.
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Affiliation(s)
- Chih-Hao Lu
- Graduate Institute of Molecular Systems Biomedicine, China Medical University, Taichung, Taiwan.
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5
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Carrondo MA, Bento I, Matias PM, Lindley PF. Crystallographic evidence for dioxygen interactions with iron proteins. J Biol Inorg Chem 2007; 12:429-42. [PMID: 17318598 DOI: 10.1007/s00775-007-0213-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2006] [Accepted: 01/29/2007] [Indexed: 10/23/2022]
Abstract
The interaction of dioxygen with iron plays a key role in many important biological processes, such as dioxygen transport in the bloodstream and the reduction of dioxygen by iron in respiration. However, the catalytic mechanisms employed, for example in ligand oxidation, are not fully understood at the current time despite intensive biochemical, spectroscopic and structural studies. This review outlines the structural evidence obtained by X-ray crystallographic methods for the nature of the interactions between dioxygen and the metal in iron-containing proteins. Proteins involved in iron transport or electron transfer are not included.
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Affiliation(s)
- M Arménia Carrondo
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Av. da República, 2781-901, Oeiras, Portugal.
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Sacquin-Mora S, Lavery R. Investigating the local flexibility of functional residues in hemoproteins. Biophys J 2006; 90:2706-17. [PMID: 16428284 PMCID: PMC1414562 DOI: 10.1529/biophysj.105.074997] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
It is now widely accepted that protein function depends not only on structure, but also on flexibility. However, the way mechanical properties contribute to catalytic mechanisms remains unclear. Here, we propose a method for investigating local flexibility within protein structures that combines a reduced protein representation with Brownian dynamics simulations. An analysis of residue fluctuations during the dynamics simulation yields a rigidity profile for the protein made up of force constants describing the ease of displacing each residue with respect to the rest of the structure. This approach has been applied to the analysis of a set of hemoproteins, one of the functionally most diverse protein families. Six proteins containing one or two heme groups have been studied, paying particular attention to the mechanical properties of the active-site residues. The calculated rigidity profiles show that active site residues are generally associated with high force constants and thus rigidly held in place. This observation also holds for diheme proteins if their mechanical properties are analyzed domain by domain. We note, however, that residues other than those in the active site can also have high force constants, as in the case of residues belonging to the folding nucleus of c-type hemoproteins.
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Affiliation(s)
- Sophie Sacquin-Mora
- Laboratoire de Biochimie Théorique, UMR 9080 CNRS, Institut de Biologie Physico-Chimique, Paris, France
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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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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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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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10
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Magistrato A, DeGrado WF, Laio A, Rothlisberger U, VandeVondele J, Klein ML. Characterization of the Dizinc Analogue of the Synthetic Diiron Protein DF1 Using ab Initio and Hybrid Quantum/Classical Molecular Dynamics Simulations. J Phys Chem B 2003. [DOI: 10.1021/jp027032o] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Alessandra Magistrato
- Center for Molecular Modeling, Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, Department of Biochemistry and Biophysics, University of Pennsylvania, School of Medicine, Philadelphia, Pennsylvania 19104-6054, CSCS, CH-6928 Manno, Switzerland, Institute of Molecular Chemistry and Biology, EPFL, CH-1025 Lausanne, Switzerland, and Laboratory for Physical Chemistry, University of Zürich CH-8057, Zürich, Switzerland
| | - William F. DeGrado
- Center for Molecular Modeling, Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, Department of Biochemistry and Biophysics, University of Pennsylvania, School of Medicine, Philadelphia, Pennsylvania 19104-6054, CSCS, CH-6928 Manno, Switzerland, Institute of Molecular Chemistry and Biology, EPFL, CH-1025 Lausanne, Switzerland, and Laboratory for Physical Chemistry, University of Zürich CH-8057, Zürich, Switzerland
| | - Alessandro Laio
- Center for Molecular Modeling, Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, Department of Biochemistry and Biophysics, University of Pennsylvania, School of Medicine, Philadelphia, Pennsylvania 19104-6054, CSCS, CH-6928 Manno, Switzerland, Institute of Molecular Chemistry and Biology, EPFL, CH-1025 Lausanne, Switzerland, and Laboratory for Physical Chemistry, University of Zürich CH-8057, Zürich, Switzerland
| | - Ursula Rothlisberger
- Center for Molecular Modeling, Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, Department of Biochemistry and Biophysics, University of Pennsylvania, School of Medicine, Philadelphia, Pennsylvania 19104-6054, CSCS, CH-6928 Manno, Switzerland, Institute of Molecular Chemistry and Biology, EPFL, CH-1025 Lausanne, Switzerland, and Laboratory for Physical Chemistry, University of Zürich CH-8057, Zürich, Switzerland
| | - Joost VandeVondele
- Center for Molecular Modeling, Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, Department of Biochemistry and Biophysics, University of Pennsylvania, School of Medicine, Philadelphia, Pennsylvania 19104-6054, CSCS, CH-6928 Manno, Switzerland, Institute of Molecular Chemistry and Biology, EPFL, CH-1025 Lausanne, Switzerland, and Laboratory for Physical Chemistry, University of Zürich CH-8057, Zürich, Switzerland
| | - Michael L. Klein
- Center for Molecular Modeling, Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, Department of Biochemistry and Biophysics, University of Pennsylvania, School of Medicine, Philadelphia, Pennsylvania 19104-6054, CSCS, CH-6928 Manno, Switzerland, Institute of Molecular Chemistry and Biology, EPFL, CH-1025 Lausanne, Switzerland, and Laboratory for Physical Chemistry, University of Zürich CH-8057, Zürich, Switzerland
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11
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Logan DT, Mulliez E, Larsson KM, Bodevin S, Atta M, Garnaud PE, Sjoberg BM, Fontecave M. A metal-binding site in the catalytic subunit of anaerobic ribonucleotide reductase. Proc Natl Acad Sci U S A 2003; 100:3826-31. [PMID: 12655046 PMCID: PMC153006 DOI: 10.1073/pnas.0736456100] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2002] [Indexed: 11/18/2022] Open
Abstract
A Zn(Cys)(4) center has been found in the C-terminal region of the crystal structure of the anaerobic class III ribonucleotide reductase (RNR) from bacteriophage T4. The metal center is structurally related to the zinc ribbon motif and to rubredoxin and rubrerythrin. Mutant enzymes of the homologous RNR from Escherichia coli, in which the coordinating cysteines, conserved in almost all known class III RNR sequences, have been mutated into alanines, are shown to be inactive as the result of their inability to generate the catalytically essential glycyl radical. The possible roles of the metal center are discussed in relationship to the currently proposed reaction mechanism for generation of the glycyl radical in class III RNRs.
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Affiliation(s)
- Derek T Logan
- Department of Molecular Biophysics, Lund University, Box 124, 221 00 Lund, Sweden.
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12
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Gomes CM, Le Gall J, Xavier AV, Teixeira M. Could a diiron-containing four-helix-bundle protein have been a primitive oxygen reductase? Chembiochem 2001; 2:583-7. [PMID: 11828492 DOI: 10.1002/1439-7633(20010803)2:7/8<583::aid-cbic583>3.0.co;2-5] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- C M Gomes
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Rua da Quinta Grande 6, Apt 127, 2780-156 Oeiras, Portugal.
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Lombardi A, Summa CM, Geremia S, Randaccio L, Pavone V, DeGrado WF. Retrostructural analysis of metalloproteins: application to the design of a minimal model for diiron proteins. Proc Natl Acad Sci U S A 2000; 97:6298-305. [PMID: 10841536 PMCID: PMC18597 DOI: 10.1073/pnas.97.12.6298] [Citation(s) in RCA: 189] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
De novo protein design provides an attractive approach for the construction of models to probe the features required for function of complex metalloproteins. The metal-binding sites of many metalloproteins lie between multiple elements of secondary structure, inviting a retrostructural approach to constructing minimal models of their active sites. The backbone geometries comprising the metal-binding sites of zinc fingers, diiron proteins, and rubredoxins may be described to within approximately 1 A rms deviation by using a simple geometric model with only six adjustable parameters. These geometric models provide excellent starting points for the design of metalloproteins, as illustrated in the construction of Due Ferro 1 (DF1), a minimal model for the Glu-Xxx-Xxx-His class of dinuclear metalloproteins. This protein was synthesized and structurally characterized as the di-Zn(II) complex by x-ray crystallography, by using data that extend to 2.5 A. This four-helix bundle protein is comprised of two noncovalently associated helix-loop-helix motifs. The dinuclear center is formed by two bridging Glu and two chelating Glu side chains, as well as two monodentate His ligands. The primary ligands are mostly buried in the protein interior, and their geometries are stabilized by a network of hydrogen bonds to second-shell ligands. In particular, a Tyr residue forms a hydrogen bond to a chelating Glu ligand, similar to a motif found in the diiron-containing R2 subunit of Escherichia coli ribonucleotide reductase and the ferritins. DF1 also binds cobalt and iron ions and should provide an attractive model for a variety of diiron proteins that use oxygen for processes including iron storage, radical formation, and hydrocarbon oxidation.
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Affiliation(s)
- A Lombardi
- Department of Chemistry, University of Napoli "Federico II," Via Mezzocannone, 4, I-80134 Napoli, Italy
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