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Dojun N, Muranishi K, Ishimori K, Uchida T. A single mutation converts Alr5027 from cyanobacteria Nostoc sp. PCC 7120 to a heme-binding protein with heme-degrading ability. J Inorg Biochem 2019; 203:110916. [PMID: 31739124 DOI: 10.1016/j.jinorgbio.2019.110916] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Revised: 10/25/2019] [Accepted: 11/08/2019] [Indexed: 11/19/2022]
Abstract
HutZ from Vibrio cholerae (VcHutZ) is a dimeric protein that catalyzes oxygen-dependent degradation of heme. The reaction mechanism is the same as that of canonical heme oxygenase (HO), but the structure of HutZ is quite different from that of HO. Thus, we postulate that HutZ has evolved via a different pathway from that of HO. The Alr5027 protein from cyanobacteria possessing proteins potentially related to ancestral proteins utilizing O2 in enzymatic reactions is homologous to HutZ family proteins (67% similarity), but the heme axial ligand of HutZ is not conserved in Alr5027. To investigate whether Alr5027 can bind and degrade heme, we expressed Alr5027 in Escherichia coli and purified it. Although Alr5027 did not bind heme, replacement of Lys164, corresponding to the heme axial ligand of HutZ, with histidine conferred heme-binding capability. The K164H mutant produced verdoheme in the reaction with H2O2, indicating acquisition of heme-degradation ability. Among the mutants, the K164H mutant produced verdoheme most efficiently. Although the K164H mutant did not degrade heme through ascorbic acid, biliverdin, the final product of VcHutZ, was formed by treatment of verdoheme with ascorbic acid. An analysis of Trp103 fluorescence indicated elongation of the distance between protomers in this mutant compared with VcHutZ-the probable cause of the inefficiency of ascorbic acid-supported heme-degradation activity. Collectively, our findings indicate that a single lysine-to-histidine mutation converted Alr5027 to a heme-binding protein that can form verdoheme through H2O2, suggesting that HutZ family proteins have acquired the heme-degradation function through molecular evolution from an ancestor protein of Alr5027.
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Affiliation(s)
- Nobuhiko Dojun
- Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo 060-8628, Japan
| | - Kazuyoshi Muranishi
- Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo 060-8628, Japan
| | - Koichiro Ishimori
- Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo 060-8628, Japan; Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan
| | - Takeshi Uchida
- Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo 060-8628, Japan; Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan.
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2
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Giardina BJ, Shahzad S, Huang W, Wilks A. Heme uptake and utilization by hypervirulent Acinetobacter baumannii LAC-4 is dependent on a canonical heme oxygenase (abHemO). Arch Biochem Biophys 2019; 672:108066. [PMID: 31398314 DOI: 10.1016/j.abb.2019.108066] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Revised: 08/02/2019] [Accepted: 08/06/2019] [Indexed: 02/06/2023]
Abstract
Acinetobacter baumannii is an opportunistic pathogen that causes serious infections in critically ill and immune compromised patients. The ability to acquire iron from the hosts iron and heme containing proteins is critical to their survival and virulence. The majority of A. baumannii hypervirulent strains encode a heme uptake system that includes a putative heme oxygenase (hemO). Despite reports indicating A. baumannii can grow on heme direct evidence of extracellular heme uptake and metabolism has not been shown. Through isotopic labeling (13C-heme) we show the hypervirulent A. baumannii LAC-4 metabolizes heme to biliverdin IXα (BVIXα), whereas ATC 17978 that lacks the hemO gene cluster cannot efficiently utilize heme. Expression and purification of the protein encoded by the A. baumannii LAC-4 hemO gene confirmed catalytic conversion of heme to BVIX. We further show inhibition of abHemO with previously characterized P. aeruginosa HemO inhibitors in a fluorescence based assay that couples HemO catalytic activity to the BVIXα binding phytochrome IFP1.4. Furthermore, the hemO gene cluster encodes genes with homology to heme-dependent extra cytoplasmic function (ECF) σ factor systems. The hemophore-dependent ECF system in Pseudomonas aeruginosa has been shown to play a critical role in heme sensing and virulence within the host. The prevalence of a hemO gene cluster in A. baumannii LAC4 and other hypervirulent strains suggests it is required within the host to adapt and utilize heme and is a major contributor to virulence.
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Affiliation(s)
- Bennett J Giardina
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, MD, 21201, USA
| | - Saba Shahzad
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, MD, 21201, USA
| | - Weiliang Huang
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, MD, 21201, USA
| | - Angela Wilks
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, MD, 21201, USA.
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3
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Samhan-Arias AK, Cordas CM, Carepo MS, Maia LB, Gutierrez-Merino C, Moura I, Moura JJG. Ligand accessibility to heme cytochrome b 5 coordinating sphere and enzymatic activity enhancement upon tyrosine ionization. J Biol Inorg Chem 2019; 24:317-330. [PMID: 30838452 DOI: 10.1007/s00775-019-01649-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2018] [Accepted: 02/21/2019] [Indexed: 01/21/2023]
Abstract
Recently, we observed that at extreme alkaline pH, cytochrome b5 (Cb5) acquires a peroxidase-like activity upon formation of a low spin hemichrome associated with a non-native state. A functional characterization of Cb5, in a wide pH range, shows that oxygenase/peroxidase activities are stimulated in alkaline media, and a correlation between tyrosine ionization and the attained enzymatic activities was noticed, associated with an altered heme spin state, when compared to acidic pH values at which the heme group is released. In these conditions, a competitive assay between imidazole binding and Cb5 endogenous heme ligands revealed the appearance of a binding site for this exogenous ligand that promotes a heme group exposure to the solvent upon ligation. Our results shed light on the mechanism behind Cb5 oxygenase/peroxidase activity stimulation in alkaline media and reveal a role of tyrosinate anion enhancing Cb5 enzymatic activities on the distorted protein before maximum protein unfolding.
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Affiliation(s)
- Alejandro K Samhan-Arias
- LAQV, REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516, Lisbon, Portugal.
| | - Cristina M Cordas
- LAQV, REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516, Lisbon, Portugal
| | - Marta S Carepo
- LAQV, REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516, Lisbon, Portugal
| | - Luisa B Maia
- LAQV, REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516, Lisbon, Portugal
| | - Carlos Gutierrez-Merino
- Department of Biochemistry and Molecular Biology, Faculty of Sciences and Institute of Molecular Pathology Biomarkers, University of Extremadura, 06006, Badajoz, Spain
| | - Isabel Moura
- LAQV, REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516, Lisbon, Portugal
| | - José J G Moura
- LAQV, REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516, Lisbon, Portugal.
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4
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Liu HX, Li L, He B, Gao SQ, Wen GB, Lin YW. Neuroglobin is capable of self-oxidation of methionine64 introduced at the heme axial position. Dalton Trans 2018; 47:10847-10852. [PMID: 30027178 DOI: 10.1039/c8dt02397b] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Neuroglobin (Ngb), with its physiological role not fully understood, was found to be capable of self-oxidation of methionine64 introduced at the heme axial position (H64M Ngb), adopting a high-spin heme state and producing both methionine sulfoxide (SO-Met) and sulfone (SO2-Met), which represents the structure and function of cytochrome c in a non-native state.
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Affiliation(s)
- Hai-Xiao Liu
- School of Chemistry and Chemical Engineering, University of South China, Hengyang 421001, China.
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5
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The Asp99-Arg188 salt bridge of the Pseudomonas aeruginosa HemO is critical in allowing conformational flexibility during catalysis. J Biol Inorg Chem 2018; 23:1057-1070. [PMID: 30194537 DOI: 10.1007/s00775-018-1609-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Accepted: 08/23/2018] [Indexed: 12/17/2022]
Abstract
The P. aeruginosa iron-regulated heme oxygenase (HemO) is required within the host for the utilization of heme as an iron source. As iron is essential for survival and virulence, HemO represents a novel antimicrobial target. We recently characterized small molecule inhibitors that bind to an allosteric site distant from the heme pocket, and further proposed binding at this site disrupts a nearby salt bridge between D99 and R188. Herein, through a combination of site-directed mutagenesis and hydrogen-deuterium exchange mass spectrometry (HDX-MS), we determined that the disruption of the D99-R188 salt bridge leads to significant decrease in conformational flexibility within the distal and proximal helices that form the heme-binding site. The RR spectra of the resting state Fe(III) and reduced Fe(II)-deoxy heme-HemO D99A, R188A and D99/R188A complexes are virtually identical to those of wild-type HemO, indicating no significant change in the heme environment. Furthermore, mutation of D99 or R188 leads to a modest decrease in the stability of the Fe(II)-O2 heme complex. Despite this slight difference in Fe(II)-O2 stability, we observe complete loss of enzymatic activity. We conclude the loss of activity is a result of decreased conformational flexibility in helices previously shown to be critical in accommodating variation in the distal ligand and the resulting chemical intermediates generated during catalysis. Furthermore, this newly identified allosteric binding site on HemO represents a novel alternative drug-design strategy to that of competitive inhibition at the active site or via direct coordination of ligands to the heme iron.
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6
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Design of artificial metalloproteins/metalloenzymes by tuning noncovalent interactions. J Biol Inorg Chem 2017; 23:7-25. [DOI: 10.1007/s00775-017-1506-8] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2017] [Accepted: 09/20/2017] [Indexed: 12/12/2022]
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7
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Li LL, Yuan H, Liao F, He B, Gao SQ, Wen GB, Tan X, Lin YW. Rational design of artificial dye-decolorizing peroxidases using myoglobin by engineering Tyr/Trp in the heme center. Dalton Trans 2017; 46:11230-11238. [DOI: 10.1039/c7dt02302b] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Artificial dye-decolorizing peroxidases (DyPs) have been rationally designed using myoglobin (Mb) as a protein scaffold by engineering Tyr/Trp in the heme center, such as F43Y/F138 W Mb, which exhibited catalytic performance comparable to some native DyPs.
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Affiliation(s)
- Le-Le Li
- School of Chemistry and Chemical Engineering
- University of South China
- Hengyang 421001
- China
| | - Hong Yuan
- Department of Chemistry & Institute of Biomedical Science
- Fudan University
- Shanghai 200433
- China
| | - Fei Liao
- School of Chemistry and Chemical Engineering
- University of South China
- Hengyang 421001
- China
| | - Bo He
- School of Chemistry and Chemical Engineering
- University of South China
- Hengyang 421001
- China
| | - Shu-Qin Gao
- Laboratory of Protein Structure and Function
- University of South China
- Hengyang 421001
- China
| | - Ge-Bo Wen
- Laboratory of Protein Structure and Function
- University of South China
- Hengyang 421001
- China
| | - Xiangshi Tan
- Department of Chemistry & Institute of Biomedical Science
- Fudan University
- Shanghai 200433
- China
| | - Ying-Wu Lin
- School of Chemistry and Chemical Engineering
- University of South China
- Hengyang 421001
- China
- Laboratory of Protein Structure and Function
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8
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Liu J, Chakraborty S, Hosseinzadeh P, Yu Y, Tian S, Petrik I, Bhagi A, Lu Y. Metalloproteins containing cytochrome, iron-sulfur, or copper redox centers. Chem Rev 2014; 114:4366-469. [PMID: 24758379 PMCID: PMC4002152 DOI: 10.1021/cr400479b] [Citation(s) in RCA: 549] [Impact Index Per Article: 54.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2013] [Indexed: 02/07/2023]
Affiliation(s)
- Jing Liu
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Saumen Chakraborty
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Parisa Hosseinzadeh
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Yang Yu
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Shiliang Tian
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Igor Petrik
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Ambika Bhagi
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Yi Lu
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
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9
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Lin YW, Sawyer EB, Wang J. Rational heme protein design: all roads lead to Rome. Chem Asian J 2013; 8:2534-44. [PMID: 23704071 DOI: 10.1002/asia.201300291] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2013] [Indexed: 01/03/2023]
Abstract
Heme proteins are among the most abundant and important metalloproteins, exerting diverse biological functions including oxygen transport, small molecule sensing, selective C-H bond activation, nitrite reduction, and electron transfer. Rational heme protein designs focus on the modification of the heme-binding active site and the heme group, protein hybridization and domain swapping, and de novo design. These strategies not only provide us with unique advantages for illustrating the structure-property-reactivity-function (SPRF) relationship of heme proteins in nature but also endow us with the ability to create novel biocatalysts and biosensors.
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Affiliation(s)
- Ying-Wu Lin
- School of Chemistry and Chemical Engineering, University of South China, Hengyang 421001 (China)
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10
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Abstract
All but a few bacterial species have an absolute need for heme, and most are able to synthesize it via a pathway that is highly conserved among all life domains. Because heme is a rich source for iron, many pathogenic bacteria have also evolved processes for sequestering heme from their hosts. The heme biosynthesis pathways are well understood at the genetic and structural biology levels. In comparison, much less is known about the heme acquisition, trafficking, and degradation processes in bacteria. Gram-positive and Gram-negative bacteria have evolved similar strategies but different tactics for importing and degrading heme, likely as a consequence of their different cellular architectures. The differences are manifested in distinct structures for molecules that perform similar functions. Consequently, the aim of this chapter is to provide an overview of the structural biology of proteins and protein-protein interactions that enable Gram-positive and Gram-negative bacteria to sequester heme from the extracellular milieu, import it to the cytosol, and degrade it to mine iron.
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Affiliation(s)
- David R Benson
- Department of Chemistry, University of Kansas, Multidisciplinary Research Building, 2030 Becker Dr., Lawrence, KS, 66047, USA,
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11
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Lin YW, You XX, Chen LS, Wu YM. Peroxidase-like Enzymes Designed from Cytochrome b5 Exhibit Enhanced Hydrolysis Activity. CHEM LETT 2012. [DOI: 10.1246/cl.2012.1574] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Ying-Wu Lin
- School of Chemistry and Chemical Engineering, University of South China
| | - Xiao-Xing You
- Institute of Pathogenic Biology, University of South China
| | - Lie-Song Chen
- Institute of Pathogenic Biology, University of South China
| | - Yi-Mou Wu
- Institute of Pathogenic Biology, University of South China
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12
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Hoy JA, Robinson H, Trent JT, Kakar S, Smagghe BJ, Hargrove MS. Plant hemoglobins: a molecular fossil record for the evolution of oxygen transport. J Mol Biol 2007; 371:168-79. [PMID: 17560601 DOI: 10.1016/j.jmb.2007.05.029] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2007] [Revised: 05/07/2007] [Accepted: 05/09/2007] [Indexed: 10/23/2022]
Abstract
The evolution of oxygen transport hemoglobins occurred on at least two independent occasions. The earliest event led to myoglobin and red blood cell hemoglobin in animals. In plants, oxygen transport "leghemoglobins" evolved much more recently. In both events, pentacoordinate heme sites capable of inert oxygen transfer evolved from hexacoordinate hemoglobins that have unrelated functions. High sequence homology between hexacoordinate and pentacoordinate hemoglobins in plants has poised them for potential structural analysis leading to a molecular understanding of this important evolutionary event. However, the lack of a plant hexacoordinate hemoglobin structure in the exogenously ligand-bound form has prevented such comparison. Here we report the crystal structure of the cyanide-bound hexacoordinate hemoglobin from barley. This presents the first opportunity to examine conformational changes in plant hexacoordinate hemoglobins upon exogenous ligand binding, and reveals structural mechanisms for stabilizing the high-energy pentacoordinate heme conformation critical to the evolution of reversible oxygen binding hemoglobins.
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Affiliation(s)
- Julie A Hoy
- Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, IA 50011, USA
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13
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Monien BH, Drepper F, Sommerhalter M, Lubitz W, Haehnel W. Detection of heme oxygenase activity in a library of four-helix bundle proteins: towards the de novo synthesis of functional heme proteins. J Mol Biol 2007; 371:739-53. [PMID: 17585935 DOI: 10.1016/j.jmb.2007.05.047] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2007] [Revised: 05/16/2007] [Accepted: 05/18/2007] [Indexed: 11/23/2022]
Abstract
Design and chemical synthesis of de novo heme proteins with enzymatic activity on cellulose membranes is described. 352 antiparallel four-helix bundle proteins with a single histidine for heme ligation were assembled from three different sets of short amphipathic helices on membrane-bound peptide templates. The templates were coupled by linkers to cellulose membranes of microplate format, which could be cleaved for control of intermediate and final products. The incorporation of heme and the heme oxygenase activity of the 352 proteins were monitored by measuring UV-visible spectra directly on the cellulose. The kinetics of the heme oxygenase reaction was studied by monitoring the decrease of the Soret band and the transient absorbance of verdoheme being an intermediate product in the formation of biliverdin. Four of the proteins covering a broad range of the enzymatic rate constants were selected and synthesized in solution for further characterization. Detailed studies by redox potentiometry, analytical ultracentrifugation, and electron paramagnetic resonance spectroscopy yielded information about the aggregation state of the proteins, the spin state and the putative coordination environment of the iron. The amount of five-coordinated high-spin iron and a positive reduction potential were found to promote the oxygenase activity of the proteins.
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Affiliation(s)
- Bernhard H Monien
- Institute of Biology II / Biochemistry, Albert-Ludwigs-Universität Freiburg, Schänzlestr. 1, D-79104 Freiburg, Germany.
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14
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Halder P, Trent JT, Hargrove MS. Influence of the protein matrix on intramolecular histidine ligation in ferric and ferrous hexacoordinate hemoglobins. Proteins 2007; 66:172-82. [PMID: 17044063 DOI: 10.1002/prot.21210] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Present in most organisms, hexacoordinate hemoglobins (hxHbs) are proteins that have evolved the capacity for reversible bis-histidyl heme coordination. The heme prosthetic group enables diverse protein functionality, such as electron transfer, redox reactions, ligand transport, and enzymatic catalysis. The reactivity of heme is greatly effected by the coordination and noncovalent chemical environment imposed by its connate protein. Of considerable interest is how the hxHb globin fold achieves reversible intramolecular coordination while still enabling high-affinity binding of oxygen, nitric oxide, and other small ligands. Here we explore this question by examining the role of the protein matrix on coordination behavior in a group of hxHbs from animals, plants, and bacteria, including human neuroglobin and cytoglobin, a nonsymbiotic hemoglobin from rice, and a truncated hemoglobin from the cyanobacterium Synechocystis. This is done with a set of experiments measuring the reduction potentials of each wild-type hxHb and its corresponding mutant protein where the reversibly bound histidine (the distal His) has been replaced with a noncoordinating side chain. These reduction potentials, coupled with studies of the mutant proteins saturated with exogenous imidazole, enable us to assess the effects of the protein matrices on histidine coordination. Our results show significant variation among the hxHbs, demonstrating flexibility in the globin moiety's ability to regulate reversible coordination. This regulation is particularly evident in the plant nonsymbiotic hemoglobins, where ferric state histidine coordination affinity is substantially lowered by the protein matrix.
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Affiliation(s)
- Puspita Halder
- Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, Iowa 50011, USA
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15
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Rath SP, Olmstead MM, Balch AL. Electron Distribution in Iron Octaethyloxophlorin Complexes. Importance of the Fe(III) Oxophlorin Trianion Form in the Bis-pyridine and Bis-imidazole Complexes. Inorg Chem 2006; 45:6083-93. [PMID: 16842017 DOI: 10.1021/ic0607033] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The apportionment of electrons between iron and the porphyrinic macrocycle in complexes of octaethyloxophlorin (H3OEPO) has been a vexing problem. In particular, for (Py)2Fe(OEPO), which is an important intermediate in heme degradation, three resonance structures involving Fe(III), Fe(II), or Fe(I), respectively, have been considered. To clarify this matter, the electronic and geometric structures of (Py)2Fe(III)(OEPO), (Im)2Fe(III)(OEPO).2THF, and (Im)2Fe(III)(OEPO).1.6CHCl3 have been examined by single-crystal X-ray diffraction, measurement of magnetic moments as a function of temperature, and EPR and NMR spectral studies. The results clearly show that both complexes exist in the Fe(III)/oxophlorin trianion form rather than the Fe(II)/oxophlorin radical form previously established for (2,6-xylylNC)(2)Fe(II)(OEPO.). In the solid state from 10 to 300 K, (Py)2Fe(III)(OEPO) exists in the high-spin (S = 5/2) state with the axial ligands in parallel planes, a planar porphyrin, and long axial Fe-N distances. However, in solution it exists predominantly in a low-spin (S = 1/2) form. In contrast, the structures of (Im)2Fe(III)(OEPO).2THF and (Im)2Fe(III)(OEPO).1.6CHCl3 consist of porphyrins with a severe ruffled distortion, axial ligands in nearly perpendicular planes, and relatively short axial Fe-N distances. The crystallographic, magnetic, EPR, and NMR results all indicate that (Im)2Fe(III)(OEPO) exists in the low-spin Fe(III) form in both the solid state and in solution.
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Affiliation(s)
- Sankar Prasad Rath
- Department of Chemistry, University of California-Davis, Davis, CA 95616, USA
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16
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Rath SP, Olmstead MM, Balch AL. Oxidative Verdoheme Formation and Stabilization by Axial Isocyanide Ligation. Inorg Chem 2004; 43:7648-55. [PMID: 15554629 DOI: 10.1021/ic0491433] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The effect of isocyanides as axial ligands on the formation and stability of verdoheme by oxidation has been examined. The reaction of [Fe(III)(OEPO)]2 with t-butyl isocyanide under dioxygen-free conditions results in the formation of (t-BuNC)2Fe(II)(OEPO*) with an electron paramagnetic resonance at g=2.009 with a peak-to-peak separation of 23.5 G at 4 K. (OEPO is the trianion of octaethyloxophlorin and OEPO* is the radical dianion obtained from OEPO by one-electron oxidation.) Exposure of chloroform solutions of either (2,6-xylylNC)2Fe(II)(OEPO*) or (t-BuNC)2Fe(II)(OEPO*) to dioxygen followed by the addition of ammonium hexafluorophosphate results in their transformation into the diamagnetic verdohemes, [(2,6-xylylNC)2Fe(II)(OEOP)](PF6) and [(t-BuNC)2Fe(II)(OEOP)](PF6), yields 68 and 70%, respectively. (OEOP is the anion of octaethyl-5-oxaporphyrin.) The oxidation reactions of (2,6-xylylNC)2Fe(II)(OEPO*) and (t-BuNC)2Fe(II)(OEPO*) have also been monitored by 1H NMR spectroscopy. No resonances due to paramagnetic products could be detected, the reactions appear to result only in the formation of the diamagnetic verdohemes, and the products are not susceptible to further oxidation.
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Affiliation(s)
- Sankar Prasad Rath
- Department of Chemistry, University of California at Davis, One Shields Avenue, Davis, California 95616, USA
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17
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Nguyen KT, Rath SP, Latos-Grazyński L, Olmstead MM, Balch AL. Formation of a Highly Oxidized Iron Biliverdin Complex upon Treatment of a Five-Coordinate Verdoheme with Dioxygen. J Am Chem Soc 2004; 126:6210-1. [PMID: 15149200 DOI: 10.1021/ja049222d] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Treatment of a green solution of the five-coordinate octaethylverdoheme, XFeII(OEOP) 1 (X = Cl or Br), with dioxygen results in the formation of a new iron complex of octaethylbiliverdin, 2, within a matter of minutes. The reaction has been monitored by 1H NMR spectroscopy, and the product 2 (X = Cl) has been isolated and examined by X-ray crystallography. The structure of 2 (X = Cl) shows that the iron is five-coordinate with bonds to the four nitrogen atoms of the helical tetrapyrrole ligand and to an axial chloride. Treatment of 2 (X = Cl or Br) with zinc amalgam produces the known iron(III) complex of biliverdin, {FeIII(OEB)}2. The unusual pattern of resonances in the 1H NMR spectrum of 2 and its facile reduction to {FeIII(OEB)}2 indicate that 2 is an oxidized complex that can be formulated by resonance structures involving either an Fe(IV) ion bound to a bilindione trianion or an Fe(III) ion bound to an oxidized, dianionic, radical form of the ligand.
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Affiliation(s)
- Khoi T Nguyen
- Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, California 95616, USA
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18
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Vu BC, Vuletich DA, Kuriakose SA, Falzone CJ, Lecomte JTJ. Characterization of the heme–histidine cross-link in cyanobacterial hemoglobins from Synechocystis sp. PCC 6803 and Synechococcus sp. PCC 7002. J Biol Inorg Chem 2004; 9:183-94. [PMID: 14727166 DOI: 10.1007/s00775-003-0512-1] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2003] [Accepted: 11/28/2003] [Indexed: 12/16/2022]
Abstract
The recombinant product of the hemoglobin gene of the cyanobacterium Synechocystis sp. PCC 6803 forms spontaneously a covalent bond linking one of the heme vinyl groups to a histidine located in the C-terminal helix (His117, or H16). The present report describes the (1)H, (15)N, and (13)C NMR spectroscopy experiments demonstrating that the recombinant hemoglobin from the cyanobacterium Synechococcus sp. PCC 7002, a protein sharing 59% identity with Synechocystis hemoglobin, undergoes the same facile heme adduct formation. The observation that the extraordinary linkage is not unique to Synechocystis hemoglobin suggests that it constitutes a noteworthy feature of hemoglobin in non-N(2)-fixing cyanobacteria, along with the previously documented bis-histidine coordination of the heme iron. A qualitative analysis of the hyperfine chemical shifts of the ferric proteins indicated that the cross-link had modest repercussions on axial histidine ligation and heme electronic structure. In Synechocystis hemoglobin, the unreacted His117 imidazole had a normal p K(a) whereas the protonation of the modified residue took place at lower pH. Optical experiments revealed that the cross-link stabilized the protein with respect to thermal and acid denaturation. Replacement of His117 with an alanine yielded a species inert to adduct formation, but inspection of the heme chemical shifts and ligand binding properties of the variant identified position 117 as important in seating the cofactor in its site and modifying the dynamic properties of the protein. A role for bis-histidine coordination and covalent adduct formation in heme retention is proposed.
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Affiliation(s)
- B Christie Vu
- Chemistry Department, The Pennsylvania State University, 152 Davey Laboratory, University Park, PA 16802, USA
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19
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Colas C, Ortiz de Montellano PR. Autocatalytic radical reactions in physiological prosthetic heme modification. Chem Rev 2003; 103:2305-32. [PMID: 12797831 DOI: 10.1021/cr0204303] [Citation(s) in RCA: 119] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Christophe Colas
- Department of Pharmaceutical Chemistry, School of Pharmacy, University of California, San Francisco, California 94143-0446, USA
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20
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Avila L, Huang HW, Damaso CO, Lu S, Moënne-Loccoz P, Rivera M. Coupled oxidation vs heme oxygenation: insights from axial ligand mutants of mitochondrial cytochrome b5. J Am Chem Soc 2003; 125:4103-10. [PMID: 12670231 DOI: 10.1021/ja029311v] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Mutation of His-39, one of the axial ligands in rat outer mitochondrial membrane cytochrome b(5) (OM cyt b(5)), to Val produces a mutant (H39V) capable of carrying out the oxidation of heme to biliverdin when incubated with hydrazine and O(2). The reaction proceeds via the formation of an oxyferrous complex (Fe(II)(-)O(2)) that is reduced by hydrazine to a ferric hydroperoxide (Fe(III)(-)OOH) species. The latter adds a hydroxyl group to the porphyrin to form meso-hydroxyheme. The observation that catalase does not inhibit the oxidation of the heme in the H39V mutant is consistent with the formation of a coordinated hydroperoxide (Fe(III)(-)OOH), which in heme oxygenase is the precursor of meso-hydroxyheme. By comparison, mutation of His-63, the other axial ligand in OM cyt b(5), to Val results in a mutant (H63V) capable of oxidizing heme to verdoheme in the absence of catalase. However, the oxidation of heme by H63V is completely inhibited by catalase. Furthermore, whereas the incubation of Fe(III)(-)H63V with H(2)O(2) leads to the nonspecific degradation of heme, the incubation of Fe(II)(-)H63V with H(2)O(2) results in the formation of meso-hydroxyheme, which upon exposure to O(2) is rapidly converted to verdoheme. These findings revealed that although meso-hydroxyheme is formed during the degradation of heme by the enzyme heme oxygenase or by the process of coupled oxidation of model hemes and hemoproteins not involved in heme catabolism, the corresponding mechanisms by which meso-hydroxyheme is generated are different. In the coupled oxidation process O(2) is reduced to noncoordinated H(2)O(2), which reacts with Fe(II)-heme to form meso-hydroxyheme. In the heme oxygenation reaction a coordinated O(2) molecule (Fe(II)(-)O(2)) is reduced to a coordinated peroxide molecule (Fe(III)(-)OOH), which oxidizes heme to meso-hydroxyheme.
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Affiliation(s)
- Ludivina Avila
- Department of Chemistry, Oklahoma State University, Stillwater, Oklahoma 74078-3071, USA
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21
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Abstract
Heme oxygenase has evolved to carry out the oxidative cleavage of heme, a reaction essential in physiological processes as diverse as iron reutilization and cellular signaling in mammals, synthesis of essential light-harvesting pigments in cyanobacteria and higher plants, and the acquisition of iron by bacterial pathogens. In all of these processes, heme oxygenase has evolved a similar structural and mechanistic scaffold to function within seemingly diverse physiological pathways. The heme oxygenase reaction is catalytically distinct from that of other hemoproteins such as the cytochromes P450, peroxidases, and catalases, but shares a hemoprotein scaffold that has evolved to generate a distinct activated oxygen species. In the following review we discuss the evolution of the structural and functional properties of heme oxygenase in light of the recent crystal structures of the mammalian and bacterial enzymes.
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Affiliation(s)
- Angela Wilks
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, MD 21201-1180, USA.
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22
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Lu Y, Berry SM, Pfister TD. Engineering novel metalloproteins: design of metal-binding sites into native protein scaffolds. Chem Rev 2001; 101:3047-80. [PMID: 11710062 DOI: 10.1021/cr0000574] [Citation(s) in RCA: 280] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- Y Lu
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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23
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Wang J, Li Y, Ma D, Kalish H, Balch AL, La Mar GN. Solution NMR determination of the seating(s) of meso-nitro-etioheme-1 in myoglobin: implications for steric constraints to meso position access in heme degradation by coupled oxidation. J Am Chem Soc 2001; 123:8080-8. [PMID: 11506564 DOI: 10.1021/ja010651a] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The highly stereoselective cleavage of hemin in myoglobin by coupled oxidation has been attributed to steric barriers that leave more space near the alpha- than the other meso-positions. The steric barriers near meso positions in myoglobin have been investigated by establishing the thermodynamics and dynamics of possible seatings in the pocket of horse myoglobin of a four-fold symmetric etioheme I modified with a bulky nitro group at a single meso position. The cyanomet complex of this reconstituted myoglobin exhibits three sets of (1)H NMR resonances that are linked dynamically and occur in approximate populations ratios of 0.82:0.10:0.08. Two dimensional (1)H NMR has been used to assign the hemin and heme pocket resonances in the major isomer in solution and to determine that the hemin is oriented with the nitro group at the canonical gamma-meso position of native hemin. The dominance of this isomer is attributed to the solvent exposure of this portion of the hemin which stabilizes the highly polar nitro group. Using a combination of magnetization transfer among methyl groups of the three isomers due to "hopping" of the hemin about its normal, the assigned resonances of an isoelectronic, bis-cyano complex of meso-nitro-etioheme I, and the known essentially constant rhombic perturbation of heme pocket sites on the hyperfine shifts of heme methyl (Kolczak, U.; Hauksson, J. B.; Davis, N. L.; Pande, U.; de Ropp, J. S.; Langry, K. C.; Smith, K. M.; LaMar, G. N. J. Am. Chem. Soc. 1999, 121, 835-843); the two minor isomers are shown to place their bulky nitro group at the canonical delta-meso (8%) and alpha-meso positions (10%). The comparable population of the isomers with nitro groups at the hydrophobic alpha- and delta-meso positions dictates that, while the static crystal structure finds more room near the alpha-meso position, the deformation at minimal energetic expense near the alpha- and delta-meso positions is comparable. These results argue that factors other than simple steric influences control the selectivity of the ring cleavage in myoglobin.
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Affiliation(s)
- J Wang
- Department of Chemistry, University of California, Davis, California 95616, USA
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Sigman JA, Wang X, Lu Y. Coupled oxidation of heme by myoglobin is mediated by exogenous peroxide. J Am Chem Soc 2001; 123:6945-6. [PMID: 11448209 DOI: 10.1021/ja015776u] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- J A Sigman
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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Kamiya N, Okimoto Y, Ding Z, Ohtomo H, Shimizu M, Kitayama A, Morii H, Nagamune T. How does heme axial ligand deletion affect the structure and the function of cytochrome b(562)? PROTEIN ENGINEERING 2001; 14:415-9. [PMID: 11477221 DOI: 10.1093/protein/14.6.415] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
We have recently generated a new mutant of cytochrome b(562) (cytb(562)) in which Met7, one of the axial heme ligands, is replaced by Ala (M7A cytb(562)). The M7A cytb(562) can bind heme and the UV-visible absorption spectrum is of a typical high-spin ferric heme. To investigate the effect of the lack of Met7 ligation on the structural integrity of cytb(562), thermal transition analyses of M7A cytb(562) were conducted. From the thermodynamic parameters obtained, it is concluded that the folding of M7A cytb(562) is comparable to the apoprotein despite the presence of heme. On the other hand, exogenous ligands such as cyanide and azide ions are readily bound to the heme iron, indicating that the axial coordination site is available for substrate binding. The peroxidase activity of this mutant is thus examined to evaluate new enzymatic function at this site and M7A cytb(562) was found to catalyze an oxidation reaction of aromatic substrates with hydrogen peroxide. These observations demonstrate that the Met7/His102 bis-ligation to the heme iron is crucial for the stable folding of cytb(562), whereas the functional conversion of cytb(562) is successfully achieved by the loose folding together with the open coordination site.
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Affiliation(s)
- N Kamiya
- Department of Chemistry and Biotechnology, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
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Lightning LK, Huang H, Moenne-Loccoz P, Loehr TM, Schuller DJ, Poulos TL, de Montellano PR. Disruption of an active site hydrogen bond converts human heme oxygenase-1 into a peroxidase. J Biol Chem 2001; 276:10612-9. [PMID: 11121422 DOI: 10.1074/jbc.m010349200] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The crystal structure of heme oxygenase-1 suggests that Asp-140 may participate in a hydrogen bonding network involving ligands coordinated to the heme iron atom. To examine this possibility, Asp-140 was mutated to an alanine, phenylalanine, histidine, leucine, or asparagine, and the properties of the purified proteins were investigated. UV-visible and resonance Raman spectroscopy indicate that the distal water ligand is lost from the iron in all the mutants except, to some extent, the D140N mutant. In the D140H mutant, the distal water ligand is replaced by the new His-140 as the sixth iron ligand, giving a bis-histidine complex. The D140A, D140H, and D140N mutants retain a trace (<3%) of biliverdin forming activity, but the D140F and D140L mutants are inactive in this respect. However, the two latter mutants retain a low ability to form verdoheme, an intermediate in the reaction sequence. All the Asp-140 mutants exhibit a new peroxidase activity. The results indicate that disruption of the distal hydrogen bonding environment by mutation of Asp-140 destabilizes the ferrous dioxygen complex and promotes conversion of the ferrous hydroperoxy intermediate obtained by reduction of the ferrous dioxygen complex to a ferryl species at the expense of its normal reaction with the porphyrin ring.
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Affiliation(s)
- L K Lightning
- Department of Pharmaceutical Chemistry, University of California, San Francisco, California 94143-0446, USA
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Ihara M, Shintaku M, Takahashi S, Ishimori K, Morishima I. Conversion of an Electron-Transfer Protein into an Oxygen Binding Protein: The Axial Cytochrome b5 Mutant with an Unusually High O2 Affinity. J Am Chem Soc 2000. [DOI: 10.1021/ja002914r] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Masaki Ihara
- Department of Molecular Engineering Graduate School of Engineering, Kyoto University Kyoto 606-8501, Japan
| | - Masato Shintaku
- Department of Molecular Engineering Graduate School of Engineering, Kyoto University Kyoto 606-8501, Japan
| | - Satoshi Takahashi
- Department of Molecular Engineering Graduate School of Engineering, Kyoto University Kyoto 606-8501, Japan
| | - Koichiro Ishimori
- Department of Molecular Engineering Graduate School of Engineering, Kyoto University Kyoto 606-8501, Japan
| | - Isao Morishima
- Department of Molecular Engineering Graduate School of Engineering, Kyoto University Kyoto 606-8501, Japan
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28
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Avila L, Huang HW, Rodríguez JC, Moënne-Loccoz P, Rivera M. Oxygen Activation by Axial Ligand Mutants of Mitochondrial Cytochrome b5: Oxidation of Heme to Verdoheme and Biliverdin. J Am Chem Soc 2000. [DOI: 10.1021/ja001137s] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Ludivina Avila
- Department of Chemistry, Oklahoma State University Stillwater, Oklahoma 74078-3071 Department of Biochemistry and Molecular Biology Oregon Graduate Institute of Science and Technology Beaverton, Oregon 97006
| | - Hong-wei Huang
- Department of Chemistry, Oklahoma State University Stillwater, Oklahoma 74078-3071 Department of Biochemistry and Molecular Biology Oregon Graduate Institute of Science and Technology Beaverton, Oregon 97006
| | - Juan C. Rodríguez
- Department of Chemistry, Oklahoma State University Stillwater, Oklahoma 74078-3071 Department of Biochemistry and Molecular Biology Oregon Graduate Institute of Science and Technology Beaverton, Oregon 97006
| | - Pierre Moënne-Loccoz
- Department of Chemistry, Oklahoma State University Stillwater, Oklahoma 74078-3071 Department of Biochemistry and Molecular Biology Oregon Graduate Institute of Science and Technology Beaverton, Oregon 97006
| | - Mario Rivera
- Department of Chemistry, Oklahoma State University Stillwater, Oklahoma 74078-3071 Department of Biochemistry and Molecular Biology Oregon Graduate Institute of Science and Technology Beaverton, Oregon 97006
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29
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Wilks A, Moënne-Loccoz P. Identification of the proximal ligand His-20 in heme oxygenase (Hmu O) from Corynebacterium diphtheriae. Oxidative cleavage of the heme macrocycle does not require the proximal histidine. J Biol Chem 2000; 275:11686-92. [PMID: 10766788 DOI: 10.1074/jbc.275.16.11686] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The coordination and spin-state of the Corynebacterium diphtheriae heme oxygenase (Hmu O) and the proximal Hmu O H20A mutant have been characterized by UV-visible and resonance Raman (RR) spectrophotometry. At neutral pH the ferric heme-Hmu O complex is a mixture of six-coordinate high spin and six-coordinate low spin species. Changes in the UV-visible and high frequency RR spectra are observed as a function of pH and temperature, with the six-coordinate high spin species being converted to six-coordinate low spin. The low frequency region of the ferrous RR spectrum identified the proximal ligand to the heme as a neutral imidazole with a Fe-His stretching mode at 222 cm(-1). The RR characterization of the heme-CO complex in wt-Hmu O confirms that the proximal imidazole is neither ionized or strongly hydrogen-bonded. Based on sequence identity with the mammalian enzymes the proximal ligand in HO-1 (His-25) and HO-2 (His-45) is conserved (His-20) in the bacterial enzyme. Site-specific mutagenesis identified His-20 as the proximal mutant based on electronic and resonance Raman spectrophotometric analysis. Titration of the heme-Hmu O complex with imidazole restored full catalytic activity to the enzyme, and the coordination of imidazole to the heme was confirmed by RR. However, in the absence of imidazole, the H20A Hmu O mutant was found to catalyze the initial alpha-meso-hydroxylation of the heme. The product of the aerobic reaction was determined to be ferrous verdoheme. Hydrolytic conversion of the verdoheme product to biliverdin concluded that oxidative cleavage of the porphyrin macrocycle was specific for the alpha-meso-carbon. The present data show that, in marked contrast to the human HO-1, the proximal ligand is not essential for the initial alpha-meso-hydroxylation of heme in the C. diphtheriae heme oxygenase-catalyzed reaction.
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Affiliation(s)
- A Wilks
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201-1180, USA.
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31
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Structures of gas-generating heme enzymes: Nitric oxide synthase and heme oxygenase. ADVANCES IN INORGANIC CHEMISTRY 2000. [DOI: 10.1016/s0898-8838(00)51005-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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