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Benchoam D, Cuevasanta E, Julió Plana L, Capece L, Banerjee R, Alvarez B. Heme-Thiolate Perturbation in Cystathionine β-Synthase by Mercury Compounds. ACS OMEGA 2021; 6:2192-2205. [PMID: 33521459 PMCID: PMC7841933 DOI: 10.1021/acsomega.0c05475] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Accepted: 12/22/2020] [Indexed: 05/11/2023]
Abstract
Cystathionine β-synthase (CBS) is an enzyme involved in sulfur metabolism that catalyzes the pyridoxal phosphate-dependent condensation of homocysteine with serine or cysteine to form cystathionine and water or hydrogen sulfide (H2S), respectively. CBS possesses a b-type heme coordinated by histidine and cysteine. Fe(III)-CBS is inert toward exogenous ligands, while Fe(II)-CBS is reactive. Both Fe(III)- and Fe(II)-CBS are sensitive to mercury compounds. In this study, we describe the kinetics of the reactions with mercuric chloride (HgCl2) and p-chloromercuribenzoic acid. These reactions were multiphasic and resulted in five-coordinate CBS lacking thiolate ligation, with six-coordinate species as intermediates. Computational QM/MM studies supported the feasibility of formation of species in which the thiolate is proximal to both the iron ion and the mercury compound. The reactions of Fe(II)-CBS were faster than those of Fe(III)-CBS. The observed rate constants of the first phase increased hyperbolically with concentration of the mercury compounds, with limiting values of 0.3-0.4 s-1 for Fe(III)-CBS and 40 ± 4 s-1 for Fe(II)-CBS. The data were interpreted in terms of alternative models of conformational selection or induced fit. Exposure of Fe(III)-CBS to HgCl2 led to heme release and activity loss. Our study reveals the complexity of the interactions between mercury compounds and CBS.
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Affiliation(s)
- Dayana Benchoam
- Laboratorio
de Enzimología, Instituto de Química Biológica,
Facultad de Ciencias, Universidad de la
República, Montevideo, 11400 Uruguay
- Centro
de Investigaciones Biomédicas (CEINBIO), Universidad de la República, Montevideo, 11800 Uruguay
| | - Ernesto Cuevasanta
- Laboratorio
de Enzimología, Instituto de Química Biológica,
Facultad de Ciencias, Universidad de la
República, Montevideo, 11400 Uruguay
- Centro
de Investigaciones Biomédicas (CEINBIO), Universidad de la República, Montevideo, 11800 Uruguay
- Unidad
de Bioquímica Analítica, Centro de Investigaciones Nucleares,
Facultad de Ciencias, Universidad de la
República, Montevideo, 11400 Uruguay
| | - Laia Julió Plana
- Departamento
de Química Inorgánica, Analítica y Química
Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires/Instituto de Química
Física de los Materiales, Medio Ambiente y Energía (INQUIMAE-CONICET), C1428EGA Buenos
Aires, Argentina
| | - Luciana Capece
- Departamento
de Química Inorgánica, Analítica y Química
Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires/Instituto de Química
Física de los Materiales, Medio Ambiente y Energía (INQUIMAE-CONICET), C1428EGA Buenos
Aires, Argentina
| | - Ruma Banerjee
- Department
of Biological Chemistry, University of Michigan
Medical School, Ann Arbor, Michigan 48109, United States
| | - Beatriz Alvarez
- Laboratorio
de Enzimología, Instituto de Química Biológica,
Facultad de Ciencias, Universidad de la
República, Montevideo, 11400 Uruguay
- Centro
de Investigaciones Biomédicas (CEINBIO), Universidad de la República, Montevideo, 11800 Uruguay
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2
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Filipovic MR, Zivanovic J, Alvarez B, Banerjee R. Chemical Biology of H 2S Signaling through Persulfidation. Chem Rev 2018; 118:1253-1337. [PMID: 29112440 PMCID: PMC6029264 DOI: 10.1021/acs.chemrev.7b00205] [Citation(s) in RCA: 599] [Impact Index Per Article: 99.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Signaling by H2S is proposed to occur via persulfidation, a posttranslational modification of cysteine residues (RSH) to persulfides (RSSH). Persulfidation provides a framework for understanding the physiological and pharmacological effects of H2S. Due to the inherent instability of persulfides, their chemistry is understudied. In this review, we discuss the biologically relevant chemistry of H2S and the enzymatic routes for its production and oxidation. We cover the chemical biology of persulfides and the chemical probes for detecting them. We conclude by discussing the roles ascribed to protein persulfidation in cell signaling pathways.
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Affiliation(s)
- Milos R. Filipovic
- Univeristy of Bordeaux, IBGC, UMR 5095, F-33077 Bordeaux, France
- CNRS, IBGC, UMR 5095, F-33077 Bordeaux, France
| | - Jasmina Zivanovic
- Univeristy of Bordeaux, IBGC, UMR 5095, F-33077 Bordeaux, France
- CNRS, IBGC, UMR 5095, F-33077 Bordeaux, France
| | - Beatriz Alvarez
- Laboratorio de Enzimología, Facultad de Ciencias and Center for Free Radical and Biomedical Research, Universidad de la Republica, 11400 Montevideo, Uruguay
| | - Ruma Banerjee
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109-0600, United States
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3
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Carballal S, Cuevasanta E, Yadav PK, Gherasim C, Ballou DP, Alvarez B, Banerjee R. Kinetics of Nitrite Reduction and Peroxynitrite Formation by Ferrous Heme in Human Cystathionine β-Synthase. J Biol Chem 2016; 291:8004-13. [PMID: 26867575 DOI: 10.1074/jbc.m116.718734] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Indexed: 01/01/2023] Open
Abstract
Cystathionine β-synthase (CBS) is a pyridoxal phosphate-dependent enzyme that catalyzes the condensation of homocysteine with serine or with cysteine to form cystathionine and either water or hydrogen sulfide, respectively. Human CBS possesses a noncatalytic heme cofactor with cysteine and histidine as ligands, which in its oxidized state is relatively unreactive. Ferric CBS (Fe(III)-CBS) can be reduced by strong chemical and biochemical reductants to Fe(II)-CBS, which can bind carbon monoxide (CO) or nitric oxide (NO(•)), leading to inactive enzyme. Alternatively, Fe(II)-CBS can be reoxidized by O2to Fe(III)-CBS, forming superoxide radical anion (O2 (̇̄)). In this study, we describe the kinetics of nitrite (NO2 (-)) reduction by Fe(II)-CBS to form Fe(II)NO(•)-CBS. The second order rate constant for the reaction of Fe(II)-CBS with nitrite was obtained at low dithionite concentrations. Reoxidation of Fe(II)NO(•)-CBS by O2showed complex kinetic behavior and led to peroxynitrite (ONOO(-)) formation, which was detected using the fluorescent probe, coumarin boronic acid. Thus, in addition to being a potential source of superoxide radical, CBS constitutes a previously unrecognized source of NO(•)and peroxynitrite.
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Affiliation(s)
- Sebastián Carballal
- From the Departamento de Bioquímica, Facultad de Medicina, Center for Free Radical and Biomedical Research, and
| | - Ernesto Cuevasanta
- Center for Free Radical and Biomedical Research, and Laboratorio de Enzimología, Facultad de Ciencias, Universidad de la República, Montevideo 11800, Uruguay and
| | - Pramod K Yadav
- the Department of Biological Chemistry, Medical Center, University of Michigan, Ann Arbor, Michigan 48109-0600
| | - Carmen Gherasim
- the Department of Biological Chemistry, Medical Center, University of Michigan, Ann Arbor, Michigan 48109-0600
| | - David P Ballou
- the Department of Biological Chemistry, Medical Center, University of Michigan, Ann Arbor, Michigan 48109-0600
| | - Beatriz Alvarez
- Center for Free Radical and Biomedical Research, and Laboratorio de Enzimología, Facultad de Ciencias, Universidad de la República, Montevideo 11800, Uruguay and
| | - Ruma Banerjee
- the Department of Biological Chemistry, Medical Center, University of Michigan, Ann Arbor, Michigan 48109-0600
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4
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Carter EL, Gupta N, Ragsdale SW. High Affinity Heme Binding to a Heme Regulatory Motif on the Nuclear Receptor Rev-erbβ Leads to Its Degradation and Indirectly Regulates Its Interaction with Nuclear Receptor Corepressor. J Biol Chem 2015; 291:2196-222. [PMID: 26670607 DOI: 10.1074/jbc.m115.670281] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2015] [Indexed: 01/11/2023] Open
Abstract
Rev-erbα and Rev-erbβ are heme-binding nuclear receptors (NR) that repress the transcription of genes involved in regulating metabolism, inflammation, and the circadian clock. Previous gene expression and co-immunoprecipitation studies led to a model in which heme binding to Rev-erbα recruits nuclear receptor corepressor 1 (NCoR1) into an active repressor complex. However, in contradiction, biochemical and crystallographic studies have shown that heme decreases the affinity of the ligand-binding domain of Rev-erb NRs for NCoR1 peptides. One explanation for this discrepancy is that the ligand-binding domain and NCoR1 peptides used for in vitro studies cannot replicate the key features of the full-length proteins used in cellular studies. However, the combined in vitro and cellular results described here demonstrate that heme does not directly promote interactions between full-length Rev-erbβ (FLRev-erbβ) and an NCoR1 construct encompassing all three NR interaction domains. NCoR1 tightly binds both apo- and heme-replete FLRev-erbβ·DNA complexes; furthermore, heme, at high concentrations, destabilizes the FLRev-erbβ·NCoR1 complex. The interaction between FLRev-erbβ and NCoR1 as well as Rev-erbβ repression at the Bmal1 promoter appear to be modulated by another cellular factor(s), at least one of which is related to the ubiquitin-proteasome pathway. Our studies suggest that heme is involved in regulating the degradation of Rev-erbβ in a manner consistent with its role in circadian rhythm maintenance. Finally, the very slow rate constant (10(-6) s(-1)) of heme dissociation from Rev-erbβ rules out a prior proposal that Rev-erbβ acts as an intracellular heme sensor.
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Affiliation(s)
- Eric L Carter
- From the Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109
| | - Nirupama Gupta
- From the Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109
| | - Stephen W Ragsdale
- From the Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109
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5
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Bagai I, Sarangi R, Fleischhacker A, Sharma A, Hoffman BM, Zuiderweg ERP, Ragsdale SW. Spectroscopic studies reveal that the heme regulatory motifs of heme oxygenase-2 are dynamically disordered and exhibit redox-dependent interaction with heme. Biochemistry 2015; 54:2693-708. [PMID: 25849895 PMCID: PMC4423204 DOI: 10.1021/bi501489r] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Revised: 03/09/2015] [Indexed: 11/28/2022]
Abstract
Heme oxygenase (HO) catalyzes a key step in heme homeostasis: the O2- and NADPH-cytochrome P450 reductase-dependent conversion of heme to biliverdin, Fe, and CO through a process in which the heme participates both as a prosthetic group and as a substrate. Mammals contain two isoforms of this enzyme, HO2 and HO1, which share the same α-helical fold forming the catalytic core and heme binding site, as well as a membrane spanning helix at their C-termini. However, unlike HO1, HO2 has an additional 30-residue N-terminus as well as two cysteine-proline sequences near the C-terminus that reside in heme regulatory motifs (HRMs). While the role of the additional N-terminal residues of HO2 is not yet understood, the HRMs have been proposed to reversibly form a thiol/disulfide redox switch that modulates the affinity of HO2 for ferric heme as a function of cellular redox poise. To further define the roles of the N- and C-terminal regions unique to HO2, we used multiple spectroscopic techniques to characterize these regions of the human HO2. Nuclear magnetic resonance spectroscopic experiments with HO2 demonstrate that, when the HRMs are in the oxidized state (HO2(O)), both the extra N-terminal and the C-terminal HRM-containing regions are disordered. However, protein NMR experiments illustrate that, under reducing conditions, the C-terminal region gains some structure as the Cys residues in the HRMs undergo reduction (HO2(R)) and, in experiments employing a diamagnetic protoporphyrin, suggest a redox-dependent interaction between the core and the HRM domains. Further, electron nuclear double resonance and X-ray absorption spectroscopic studies demonstrate that, upon reduction of the HRMs to the sulfhydryl form, a cysteine residue from the HRM region ligates to a ferric heme. Taken together with EPR measurements, which show the appearance of a new low-spin heme signal in reduced HO2, it appears that a cysteine residue(s) in the HRMs directly interacts with a second bound heme.
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Affiliation(s)
- Ireena Bagai
- Department
of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48019, United States
| | - Ritimukta Sarangi
- Stanford
Synchrotron
Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - Angela
S. Fleischhacker
- Department
of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48019, United States
| | - Ajay Sharma
- Department
of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Brian M. Hoffman
- Department
of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Erik R. P. Zuiderweg
- Department
of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48019, United States
| | - Stephen W. Ragsdale
- Department
of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48019, United States
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6
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Ishimori K, Watanabe Y. Unique Heme Environmental Structures in Heme-regulated Proteins Using Heme as the Signaling Molecule. CHEM LETT 2014. [DOI: 10.1246/cl.140787] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Affiliation(s)
| | - Yuta Watanabe
- Department of Chemistry, Faculty of Science, Hokkaido University
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7
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Vicente JB, Colaço HG, Mendes MIS, Sarti P, Leandro P, Giuffrè A. NO* binds human cystathionine β-synthase quickly and tightly. J Biol Chem 2014; 289:8579-87. [PMID: 24515102 DOI: 10.1074/jbc.m113.507533] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The hexa-coordinate heme in the H2S-generating human enzyme cystathionine β-synthase (CBS) acts as a redox-sensitive regulator that impairs CBS activity upon binding of NO(•) or CO at the reduced iron. Despite the proposed physiological relevance of this inhibitory mechanism, unlike CO, NO(•) was reported to bind at the CBS heme with very low affinity (Kd = 30-281 μm). This discrepancy was herein reconciled by investigating the NO(•) reactivity of recombinant human CBS by static and stopped-flow UV-visible absorption spectroscopy. We found that NO(•) binds tightly to the ferrous CBS heme, with an apparent Kd ≤ 0.23 μm. In line with this result, at 25 °C, NO(•) binds quickly to CBS (k on ∼ 8 × 10(3) m(-1) s(-1)) and dissociates slowly from the enzyme (k off ∼ 0.003 s(-1)). The observed rate constants for NO(•) binding were found to be linearly dependent on [NO(•)] up to ∼ 800 μm NO(•), and >100-fold higher than those measured for CO, indicating that the reaction is not limited by the slow dissociation of Cys-52 from the heme iron, as reported for CO. For the first time the heme of human CBS is reported to bind NO(•) quickly and tightly, providing a mechanistic basis for the in vivo regulation of the enzyme by NO(•). The novel findings reported here shed new light on CBS regulation by NO(•) and its possible (patho)physiological relevance, enforcing the growing evidence for an interplay among the gasotransmitters NO(•), CO, and H2S in cell signaling.
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Affiliation(s)
- João B Vicente
- From the Metabolism and Genetics Group, Research Institute for Medicines and Pharmaceutical Sciences (iMed.UL), Faculty of Pharmacy, University of Lisbon, 1649-003 Lisbon, Portugal
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8
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Saha R, Bose M, Sen Santara S, Roy J, Adak S. Identification of proximal and distal axial ligands in Leishmania major pseudoperoxidase. Biochemistry 2013; 52:8878-87. [PMID: 24261670 DOI: 10.1021/bi401343t] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Previous optical and electron paramagnetic resonance (EPR) spectroscopic studies of the newly discovered peroxynitrite scavenging pseudoperoxidase from Leishmania major (LmPP) suggested that ferric LmPP contained a six-coordinate low-spin (6cLS) heme with a thiolate ligand, presumably a cysteine, bound to its heme iron. To identify the axial ligands of LmPP, we exploit a systematic mutational analysis of potential heme ligands. On the basis of UV-visible and EPR spectroscopy, we report that the substitution of the proximal His206 with alanine in LmPP alters the 6cLS to a five-coordinate high spin (5cHS) form at pH 4.0 that has a spectrum characteristic of a Cys-ligated 5cHS derivative. The electronic absorption and EPR analysis of all alanine-substituted Cys and Met single mutants establish that when Cys107 is replaced with alanine, a new species appears that has a spectrum characteristic of a histidine-ligated 5cHS derivative at pH 4.0. Together, these results suggest that His206 and Cys107 act as the proximal and distal axial ligands in ferric LmPP, respectively. However, the electronic properties of reduced wild-type LmPP are similar to those of known 5cHS His-ligated heme proteins at pH 8.8, indicating that the thiolate bond was broken upon reduction. Furthermore, the wild-type protein was only partially reduced at pH 4.0, but the E105L mutant was completely reduced to form a 5cHS ferrous heme. These results imply that the presence of an acidic residue near the distal site may prevent reduction of the heme iron at acidic pH.
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Affiliation(s)
- Rina Saha
- Division of Structural Biology and Bio-informatics, CSIR-Indian Institute of Chemical Biology , 4, Raja S. C. Mullick Road, Kolkata 700 032, India
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9
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Yadav PK, Xie P, Banerjee R. Allosteric communication between the pyridoxal 5'-phosphate (PLP) and heme sites in the H2S generator human cystathionine β-synthase. J Biol Chem 2012; 287:37611-20. [PMID: 22977242 DOI: 10.1074/jbc.m112.414706] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Human cystathionine β-synthase (CBS) is a unique pyridoxal 5'-phosphate (PLP)-dependent enzyme that has a regulatory heme cofactor. Previous studies have demonstrated the importance of Arg-266, a residue at the heme pocket end of α-helix 8, for communication between the heme and PLP sites. In this study, we have examined the role of the conserved Thr-257 and Thr-260 residues, located at the other end of α-helix 8 on the heme electronic environment and on activity. The mutations at the two positions destabilize PLP binding, leading to lower PLP content and ~2- to ~500-fold lower activity compared with the wild-type enzyme. Activity is unresponsive to PLP supplementation, consistent with the pyridoxine-nonresponsive phenotype of the T257M mutation in a homocystinuric patient. The H(2)S-producing activities, also impacted by the mutations, show a different pattern of inhibition compared with the canonical transsulfuration reaction. Interestingly, the mutants exhibit contrasting sensitivities to the allosteric effector, S-adenosylmethionine (AdoMet); whereas T257M and T257I are inhibited, the other mutants are hyperactivated by AdoMet. All mutants showed an increased propensity of the ferrous heme to form an inactive species with a 424 nm Soret peak and exhibited significantly reduced enzyme activity in the ferrous and ferrous-CO states. Our results provide the first evidence for bidirectional transmission of information between the cofactor binding sites, suggest the additional involvement of this region in allosteric communication with the regulatory AdoMet-binding domain, and reveal the potential for independent modulation of the canonical transsulfuration versus H(2)S-generating reactions catalyzed by CBS.
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Affiliation(s)
- Pramod Kumar Yadav
- Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan 48109-0600, USA
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10
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Kabil O, Weeks CL, Carballal S, Gherasim C, Alvarez B, Spiro TG, Banerjee R. Reversible heme-dependent regulation of human cystathionine β-synthase by a flavoprotein oxidoreductase. Biochemistry 2011; 50:8261-3. [PMID: 21875066 DOI: 10.1021/bi201270q] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Human CBS is a PLP-dependent enzyme that clears homocysteine, gates the flow of sulfur into glutathione, and contributes to the biogenesis of H(2)S. The presence of a heme cofactor in CBS is enigmatic, and its conversion from the ferric- to ferrous-CO state inhibits enzyme activity. The low heme redox potential (-350 mV) has raised questions about the feasibility of the ferrous-CO state forming under physiological conditions. Herein, we provide the first evidence of reversible inhibition of CBS by CO in the presence of a human flavoprotein and NADPH. These data provide a mechanism for cross talk between two gas-signaling systems, CO and H(2)S, via heme-mediated allosteric regulation of CBS.
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Affiliation(s)
- Omer Kabil
- Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan 48109-0600, United States
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11
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Smith AT, Majtan T, Freeman KM, Su Y, Kraus JP, Burstyn JN. Cobalt cystathionine β-synthase: a cobalt-substituted heme protein with a unique thiolate ligation motif. Inorg Chem 2011; 50:4417-27. [PMID: 21480614 PMCID: PMC3350334 DOI: 10.1021/ic102586b] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Human cystathionine β-synthase (hCBS), a key enzyme in the trans-sulfuration pathway, catalyzes the condensation of serine with homocysteine to produce cystathionine. CBS from higher organisms is the only known protein that binds pyridoxal-5'-phosphate (PLP) and heme. Intriguingly, the function of the heme in hCBS has yet to be elucidated. Herein, we describe the characterization of a cobalt-substituted variant of hCBS (Co hCBS) in which CoPPIX replaces FePPIX (heme). Co(III) hCBS is a unique Co-substituted heme protein: the Co(III) ion is 6-coordinate, low-spin, diamagnetic, and bears a cysteine(thiolate) as one of its axial ligands. The peak positions and intensities of the electronic absorption and MCD spectra of Co(III) hCBS are distinct from those of previously Co-substituted heme proteins; TD-DFT calculations reveal that the unique features arise from the 6-coordinate Co bound axially by cysteine(thiolate) and a neutral donor, presumably histidine. Reactivity of Co(III) hCBS with HgCl(2) is consistent with a loss of the cysteine(thiolate) ligand. Co(III) hCBS is slowly reduced to Co(II) hCBS, which contains a 5-coordinate, low-spin, S = 1/2 Co-porphyrin that does not retain the cysteine(thiolate) ligand; this form of Co(II) hCBS binds NO((g)) but not CO((g)). Co(II) hCBS is reoxidized in the air to form a new Co(III) form, which does not contain a cysteine(thiolate) ligand. Canonical and alternative CBS assays suggest that maintaining the native heme ligation motif of wild-type Fe hCBS (Cys/His) is essential in maintaining maximal activity in Co hCBS. Correlation between the coordination structures and enzyme activity in both native Fe and Co-substituted proteins implicates a structural role for the heme in CBS.
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Affiliation(s)
- Aaron T. Smith
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Ave., Madison, Wisconsin, 53706 USA
| | - Tomas Majtan
- Department of Pediatrics, University of Colorado Denver, Aurora, Colorado 80045
- Department of Genomics & Biotechnology, Institute of Molecular Biology SAS, Dubravska cesta 21, Bratislava, 84551, Slovakia
| | - Katherine M. Freeman
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Ave., Madison, Wisconsin, 53706 USA
| | - Yang Su
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Ave., Madison, Wisconsin, 53706 USA
| | - Jan P. Kraus
- Department of Pediatrics, University of Colorado Denver, Aurora, Colorado 80045
| | - Judith N. Burstyn
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Ave., Madison, Wisconsin, 53706 USA
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12
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Ishikawa H, Nakagaki M, Bamba A, Uchida T, Hori H, O'Brian MR, Iwai K, Ishimori K. Unusual heme binding in the bacterial iron response regulator protein: spectral characterization of heme binding to the heme regulatory motif. Biochemistry 2011; 50:1016-22. [PMID: 21192735 DOI: 10.1021/bi101895r] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We characterized heme binding in the bacterial iron response regulator (Irr) protein, which is a simple heme-regulated protein having a single "heme-regulatory motif", HRM, and plays a key role in the iron homeostasis of a nitrogen-fixing bacterium. The heme titration to wild-type and mutant Irr clearly showed that Irr has two heme binding sites: one of the heme binding sites is in the HRM, where (29)Cys is the axial ligand, and the other one, the secondary heme binding site, is located outside of the HRM. The Raman line for the Fe-S stretching mode observed at 333 cm(-1) unambiguously confirmed heme binding to Cys. The lower frequency of the Fe-S stretching mode corresponds to the weaker Fe-S bond, and the broad Raman line of the Fe-S bond suggests multiple configurations of heme binding. These structural characteristics are definitely different from those of typical hemoproteins. The unusual heme binding in Irr was also evident in the EPR spectra. The characteristic g-values of the 5-coordinate Cys-ligated heme and 6-coordinate His/His-ligated heme were observed, while the multiple configurations of heme binding were also confirmed. Such multiple heme configurations are not encountered for typical hemoproteins where the heme functions as the active center. Therefore, we conclude that heme binding to HRM in the heme-regulated protein, Irr, is quite different from that in conventional hemoproteins but characteristic of heme-regulated proteins using heme as the signaling molecule.
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Affiliation(s)
- Haruto Ishikawa
- Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Kyoto 615-8530, Japan
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13
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Ukita S, Fujii T, Hira D, Nishiyama T, Kawase T, Migita CT, Furukawa K. A heterodimeric cytochrome c complex with a very low redox potential from an anaerobic ammonium-oxidizing enrichment culture. FEMS Microbiol Lett 2010; 313:61-7. [PMID: 20883501 DOI: 10.1111/j.1574-6968.2010.02122.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
A dimeric cytochrome c with an apparent molecular mass of 25 kDa was isolated from an anammox bacterium, strain KSU-1, in a relatively large quantity. This protein was named the NaxLS complex. The spectrum of the oxidized form exhibited a peculiar Soret peak at 419 nm. The reduction of NaxLS was not complete even with the addition of excess dithionite, but was complete with titanium (III) citrate, indicating that the NaxLS complex has a very low redox potential. The genes encoding the two subunits, naxL and naxS, are adjacent on the genome. The deduced amino-acid sequences of the genes showed high identities with those of two genes encoding 'unknown proteins' in the genome of Candidatus Kuenenia stuttgartiensis, but had lower identities with other c-type heme proteins. The electron paramagnetic resonance spectra of NaxLS exhibited low-spin signals of two heme species in the range between g=2.6 and g=1.8, which strongly suggested an unusual His/Cys coordination. This unique coordination might account for the low redox potential of the hemes in NaxLS. NaxLS might participate in the transfer of low redox potential electrons in the intracellular anammoxosome compartment or the cytoplasm.
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Affiliation(s)
- Saki Ukita
- Department of Applied Life Science, Faculty of Biotechnology and Life Science, Sojo University, Ikeda, Kumamoto, Japan
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14
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Karunakaran V, Benabbas A, Sun Y, Zhang Z, Singh S, Banerjee R, Champion PM. Investigations of low-frequency vibrational dynamics and ligand binding kinetics of cystathionine beta-synthase. J Phys Chem B 2010; 114:3294-306. [PMID: 20155941 DOI: 10.1021/jp909700r] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Vibrational coherence spectroscopy is used to study the low frequency dynamics of the truncated dimer of human cystathionine beta-synthase (CBS). CBS is a pyridoxal-5'-phosphate-dependent heme enzyme with cysteine and histidine axial ligands that catalyzes the condensation of serine and homocysteine to form cystathionine. A strong correlation between the "detuned" coherence spectrum (which probes higher frequencies) and the Raman spectrum is demonstrated, and a rich pattern of modes below 200 cm(-1) is revealed. Normal coordinate structural decomposition (NSD) of the ferric CBS crystal structure predicts the enhancement of normal modes with significant heme "doming", "ruffling", and "saddling" content, and they are observed in the coherence spectra near approximately 40, approximately 60, and approximately 90 cm(-1). When pH is varied, the relative intensities and frequencies of the low frequency heme modes indicate the presence of a unique protein-induced heme structural perturbation near pH 7 that differs from what is observed at higher or lower pH. For ferric CBS, we observe a new mode near approximately 25 cm(-1), possibly involving the response of the protein, which exhibits a phase jump of approximately pi for excitation on the blue and red side of the Soret band maximum. The low frequency vibrational coherence spectrum of ferrous CBS is also presented, along with our efforts to probe its NO-bound complex. The CO geminate rebinding kinetics of CBS are similar to the CO-bound form of the gene activator protein CooA, but with the appearance of a significant additional kinetic inhomogeneity. Analysis of this inhomogeneity suggests that it arises from the two subunits of CBS and leads to a factor of approximately 20 for the ratio of the average CO geminate rebinding rates of the two subunits.
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Affiliation(s)
- Venugopal Karunakaran
- Department of Physics and Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston, Massachusetts 02115, USA
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15
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Celano L, Gil M, Carballal S, Durán R, Denicola A, Banerjee R, Alvarez B. Inactivation of cystathionine beta-synthase with peroxynitrite. Arch Biochem Biophys 2009; 491:96-105. [PMID: 19733148 DOI: 10.1016/j.abb.2009.08.022] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2009] [Revised: 08/26/2009] [Accepted: 08/28/2009] [Indexed: 11/19/2022]
Abstract
Cystathionine beta-synthase (CBS) is a homocysteine metabolizing enzyme that contains pyridoxal phosphate (PLP) and a six-coordinate heme cofactor of unknown function. CBS was inactivated by peroxynitrite, the product of nitric oxide and superoxide radicals. The IC(50) was approximately 150microM for 5microM ferric CBS. Stopped-flow kinetics and competition experiments showed a direct reaction with a second-order rate constant of (2.4-5.0)x10(4)M(-1)s(-1) (pH 7.4, 37 degrees C). The radicals derived from peroxynitrite, nitrogen dioxide and carbonate radical, also inactivated CBS. Exposure to peroxynitrite did not modify bound PLP but led to nitration of Trp208, Trp43 and Tyr223 and alterations in the heme environment including loss of thiolate coordination, conversion to high-spin and bleaching, with no detectable formation of oxo-ferryl compounds nor promotion of one-electron processes. This study demonstrates the susceptibility of CBS to reactive oxygen/nitrogen species, with potential relevance to hyperhomocysteinemia, a risk factor for cardiovascular diseases.
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Affiliation(s)
- Laura Celano
- Laboratorio de Enzimología, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay
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16
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Singh S, Madzelan P, Stasser J, Weeks CL, Becker D, Spiro TG, Penner-Hahn J, Banerjee R. Modulation of the heme electronic structure and cystathionine beta-synthase activity by second coordination sphere ligands: The role of heme ligand switching in redox regulation. J Inorg Biochem 2009; 103:689-97. [PMID: 19232736 DOI: 10.1016/j.jinorgbio.2009.01.009] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2008] [Revised: 01/05/2009] [Accepted: 01/07/2009] [Indexed: 11/30/2022]
Abstract
In humans, cystathionine beta-synthase (CBS) is a hemeprotein, which catalyzes a pyridoxal phosphate (PLP)-dependent condensation reaction. Changes in the heme environment are communicated to the active site, which is approximately 20A away. In this study, we have examined the role of H67 and R266, which are in the second coordination sphere of the heme ligands, H65 and C52, respectively, in modulating the heme's electronic properties and in transmitting information between the heme and active sites. While the H67A mutation is comparable to wild-type CBS, interesting differences are revealed by mutations at the R266 site. The pathogenic mutant, R266K, is moderately PLP-responsive while the R266M mutation shows dramatic differences in the ferrous state. The electrostatic interaction between C52 and R266 is critical for stabilizing the ferrous heme and its disruption leads to the facile formation of a 424nm (C-424) absorbing ferrous species, which is inactive, compared to the active 449nm ferrous species for wild-type CBS. Resonance Raman studies on the R266M mutant reveal that the kinetics of C52 rebinding after Fe-CO photolysis are comparable to that of wild-type CBS. EXAFS studies on C-424 CBS are consistent with the presence of two axial N/O low Z scatters with only one being a rigid unit of a histidine residue while the other could be a solvent molecule, an oxygen atom from the peptide backbone or a side chain nitrogen. The redox potential for the heme in full-length CBS is -350+/-4mV and is substantially lower than the value of -287+/-2mV determined for truncated CBS. A redox-regulated ligand change has the potential to serve as an allosteric on/off switch in human CBS and the second sphere ligand, R266, plays an important role in this transition.
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Affiliation(s)
- Sangita Singh
- Department of Biological Chemistry, University of Michigan, Ann Arbor, 48109-0606, United States
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17
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Moreira LM, Poli AL, Costa-Filho AJ, Imasato H. Ferric species equilibrium of the giant extracellular hemoglobin of Glossoscolex paulistus in alkaline medium: HALS hemichrome as a precursor of pentacoordinate species. Int J Biol Macromol 2008; 42:103-10. [DOI: 10.1016/j.ijbiomac.2007.10.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2007] [Revised: 09/10/2007] [Accepted: 10/01/2007] [Indexed: 11/25/2022]
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18
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Ozaki SI, Doi M, Migita CT. Modulation of Cystathionine β-Synthase Activity by Altering Heme Environment. CHEM LETT 2008. [DOI: 10.1246/cl.2008.208] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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19
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Singh S, Madzelan P, Banerjee R. Properties of an unusual heme cofactor in PLP-dependent cystathionine beta-synthase. Nat Prod Rep 2007; 24:631-9. [PMID: 17534535 DOI: 10.1039/b604182p] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Affiliation(s)
- Sangita Singh
- Redox Biology Center and Department of Biochemistry, University of Nebraska, Lincoln, NE 68588-0664, USA
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20
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Marmo Moreira L, Lima Poli A, Costa-Filho AJ, Imasato H. Pentacoordinate and hexacoordinate ferric hemes in acid medium: EPR, UV–Vis and CD studies of the giant extracellular hemoglobin of Glossoscolex paulistus. Biophys Chem 2006; 124:62-72. [PMID: 16814451 DOI: 10.1016/j.bpc.2006.05.030] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2006] [Revised: 05/30/2006] [Accepted: 05/30/2006] [Indexed: 11/26/2022]
Abstract
The equilibrium complexity involving different axially coordinated hemes is peculiar to hemoglobins. The pH dependence of the spontaneous exchange of ligands in the extracellular hemoglobin from Glossoscolex paulistus was studied using UV-Vis, EPR, and CD spectroscopies. This protein has a complex oligomeric assembly with molecular weight of 3.1 MDa that presents an important cooperative effect. A complex coexistence of different species was observed in almost all pH values, except pH 7.0, where just aquomet species is present. Four new species were formed and coexist with the aquomethemoglobin upon acidification: (i) a "pure" low-spin hemichrome (Type II), also called hemichrome B, with an usual spin state (d(xy))(2)(d(xz),d(yz))(3); (ii) a strong g(max) hemichrome (Type I), also showing an usual spin state (d(xy))(2)(d(xz),d(yz))(3); (iii) a hemichrome with unusual spin state (d(xz),d(yz))(4)(d(xy))(1) (Type III); (iv) and a high-spin pentacoordinate species. CD measurements suggest that the mechanism of species formation could be related with an initial process of acid denaturation. However, it is worth mentioning that based on EPR the aquomet species remains even at acidic pH, indicating that the transitions are not complete. The "pure" low-spin hemichrome presents a parallel orientation of the imidazole ring planes but the strong g(max) hemichrome is a HALS (highly anisotropic low-spin) species indicating a reciprocally perpendicular orientation of the imidazole ring planes. The hemichromes and pentacoordinate formation mechanisms are discussed in detail.
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Affiliation(s)
- Leonardo Marmo Moreira
- Instituto de Química de São Carlos, Universidade de São Paulo, CEP 13566-590, São Carlos, SP, Brazil
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21
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Fiorucci S, Distrutti E, Cirino G, Wallace JL. The emerging roles of hydrogen sulfide in the gastrointestinal tract and liver. Gastroenterology 2006; 131:259-71. [PMID: 16831608 DOI: 10.1053/j.gastro.2006.02.033] [Citation(s) in RCA: 280] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/12/2005] [Accepted: 02/15/2006] [Indexed: 02/07/2023]
Abstract
Hydrogen sulfide, like nitric oxide, was best known as a toxic pollutant before becoming recognized as a key regulator of several physiologic processes. In recent years, evidence has accumulated to suggest important roles for hydrogen sulfide as a mediator of several aspects of gastrointestinal and liver function. Moreover, alterations in hydrogen sulfide production could contribute to disorders of the gastrointestinal tract and liver. For example, nonsteroidal anti-inflammatory drugs can reduce production of hydrogen sulfide in the stomach, and this has been shown to contribute to the generation of mucosal injury. Hydrogen sulfide has also been shown to play a key role in modulation of visceral hyperalgesia. Inhibitors of hydrogen sulfide synthesis and drugs that can generate safe levels of hydrogen sulfide in vivo have been developed and are permitting interventional studies in experimental models and, in the near future, humans.
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Affiliation(s)
- Stefano Fiorucci
- Dipartimenti di Medicina Clinica and Patologia, University of Perugia, Perugia, Italy
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22
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Banerjee R, Zou CG. Redox regulation and reaction mechanism of human cystathionine-beta-synthase: a PLP-dependent hemesensor protein. Arch Biochem Biophys 2005; 433:144-56. [PMID: 15581573 DOI: 10.1016/j.abb.2004.08.037] [Citation(s) in RCA: 167] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2004] [Revised: 08/16/2004] [Indexed: 10/26/2022]
Abstract
Cystathionine beta-synthase in mammals lies at a pivotal crossroad in methionine metabolism directing flux toward cysteine synthesis and catabolism. The enzyme exhibits a modular organization and complex regulation. It catalyzes the beta-replacement of the hydroxyl group of serine with the thiolate of homocysteine and is unique in being the only known pyridoxal phosphate-dependent enzyme that also contains heme b as a cofactor. The heme functions as a sensor and modulates enzyme activity in response to redox change and to CO binding. Mutations in this enzyme are the single most common cause of hereditary hyperhomocysteinemia. Elucidation of the crystal structure of a truncated and highly active form of the human enzyme containing the heme- and pyridoxal phosphate binding domains has afforded a structural perspective on mechanistic and mutation analysis studies. The C-terminal regulatory domain containing two CBS motifs exerts intrasteric regulation and binds the allosteric activator, S-adenosylmethionine. Studies with mammalian cells in culture as well as with animal models have unraveled multiple layers of regulation of cystathionine beta-synthase in response to redox perturbations and reveal the important role of this enzyme in glutathione-dependent redox homestasis. This review discusses the recent advances in our understanding of the structure, mechanism, and regulation of cystathionine beta-synthase from the perspective of its physiological function, focusing on the clinically relevant human enzyme.
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Affiliation(s)
- Ruma Banerjee
- Department of Biochemistry, University of Nebraska, Lincoln, NE 68588-0664, USA.
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23
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Miles EW, Kraus JP. Cystathionine beta-synthase: structure, function, regulation, and location of homocystinuria-causing mutations. J Biol Chem 2004; 279:29871-4. [PMID: 15087459 DOI: 10.1074/jbc.r400005200] [Citation(s) in RCA: 172] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Affiliation(s)
- Edith Wilson Miles
- NIDDK, National Institutes of Health, Bethesda, Maryland 20892-0830, USA
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24
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Igarashi J, Sato A, Kitagawa T, Yoshimura T, Yamauchi S, Sagami I, Shimizu T. Activation of heme-regulated eukaryotic initiation factor 2alpha kinase by nitric oxide is induced by the formation of a five-coordinate NO-heme complex: optical absorption, electron spin resonance, and resonance raman spectral studies. J Biol Chem 2004; 279:15752-62. [PMID: 14752110 DOI: 10.1074/jbc.m310273200] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Heme-regulated eukaryotic initiation factor 2alpha kinase (HRI) regulates the synthesis of hemoglobin in reticulocytes in response to heme availability. HRI contains a tightly bound heme at the N-terminal domain. Earlier reports show that nitric oxide (NO) regulates HRI catalysis. However, the mechanism of this process remains unclear. In the present study, we utilize in vitro kinase assays, optical absorption, electron spin resonance (ESR), and resonance Raman spectra of purified full-length HRI for the first time to elucidate the regulation mechanism of NO. HRI was activated via heme upon NO binding, and the Fe(II)-HRI(NO) complex displayed 5-fold greater eukaryotic initiation factor 2alpha kinase activity than the Fe(III)-HRI complex. The Fe(III)-HRI complex exhibited a Soret peak at 418 nm and a rhombic ESR signal with g values of 2.49, 2.28, and 1.87, suggesting coordination with Cys as an axial ligand. Interestingly, optical absorption, ESR, and resonance Raman spectra of the Fe(II)-NO complex were characteristic of five-coordinate NO-heme. Spectral findings on the coordination structure of full-length HRI were distinct from those obtained for the isolated N-terminal heme-binding domain. Specifically, six-coordinate NO-Fe(II)-His was observed but not Cys-Fe(III) coordination. It is suggested that significant conformational change(s) in the protein induced by NO binding to the heme lead to HRI activation. We discuss the role of NO and heme in catalysis by HRI, focusing on heme-based sensor proteins.
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Affiliation(s)
- Jotaro Igarashi
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan
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25
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Banerjee R, Evande R, Kabil O, Ojha S, Taoka S. Reaction mechanism and regulation of cystathionine beta-synthase. BIOCHIMICA ET BIOPHYSICA ACTA 2003; 1647:30-5. [PMID: 12686104 DOI: 10.1016/s1570-9639(03)00044-x] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In mammals, cystathionine beta-synthase catalyzes the first step in the transsulfuration pathway which provides an avenue for the conversion of the essential amino acid, methionine, to cysteine. Cystathionine beta-synthase catalyzes a PLP-dependent condensation of serine and homocysteine to cystathionine and is unique in also having a heme cofactor. In this review, recent advances in our understanding of the kinetic mechanism of the yeast and human enzymes as well as pathogenic mutants of the human enzyme and insights into the role of heme in redox sensing are discussed from the perspective of the crystal structure of the catalytic core of the human enzyme.
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Affiliation(s)
- Ruma Banerjee
- Biochemistry Department, University of Nebraska, Lincoln, NE 68588-0664, USA.
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26
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Bamford VA, Bruno S, Rasmussen T, Appia-Ayme C, Cheesman MR, Berks BC, Hemmings AM. Structural basis for the oxidation of thiosulfate by a sulfur cycle enzyme. EMBO J 2002; 21:5599-610. [PMID: 12411478 PMCID: PMC131063 DOI: 10.1093/emboj/cdf566] [Citation(s) in RCA: 118] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Reduced inorganic sulfur compounds are utilized by many bacteria as electron donors to photosynthetic or respiratory electron transport chains. This metabolism is a key component of the biogeochemical sulfur cycle. The SoxAX protein is a heterodimeric c-type cytochrome involved in thiosulfate oxidation. The crystal structures of SoxAX from the photosynthetic bacterium Rhodovulum sulfidophilum have been solved at 1.75 A resolution in the oxidized state and at 1.5 A resolution in the dithionite-reduced state, providing the first structural insights into the enzymatic oxidation of thiosulfate. The SoxAX active site contains a haem with unprecedented cysteine persulfide (cysteine sulfane) coordination. This unusual post-translational modification is also seen in sulfurtransferases such as rhodanese. Intriguingly, this enzyme shares further active site characteristics with SoxAX such as an adjacent conserved arginine residue and a strongly positive electrostatic potential. These similarities have allowed us to suggest a catalytic mechanism for enzymatic thiosulfate oxidation. The atomic coordinates and experimental structure factors have been deposited in the PDB with the accession codes 1H31, 1H32 and 1H33.
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Affiliation(s)
- Vicki A. Bamford
- Centre for Metalloprotein Spectroscopy and Biology,
School of Biological Sciences and School of Chemical Sciences, University of East Anglia, Norwich NR4 7TJ and Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK Corresponding authors e-mail: or
| | - Stefano Bruno
- Centre for Metalloprotein Spectroscopy and Biology,
School of Biological Sciences and School of Chemical Sciences, University of East Anglia, Norwich NR4 7TJ and Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK Corresponding authors e-mail: or
| | - Tim Rasmussen
- Centre for Metalloprotein Spectroscopy and Biology,
School of Biological Sciences and School of Chemical Sciences, University of East Anglia, Norwich NR4 7TJ and Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK Corresponding authors e-mail: or
| | - Corinne Appia-Ayme
- Centre for Metalloprotein Spectroscopy and Biology,
School of Biological Sciences and School of Chemical Sciences, University of East Anglia, Norwich NR4 7TJ and Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK Corresponding authors e-mail: or
| | - Myles R. Cheesman
- Centre for Metalloprotein Spectroscopy and Biology,
School of Biological Sciences and School of Chemical Sciences, University of East Anglia, Norwich NR4 7TJ and Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK Corresponding authors e-mail: or
| | - Ben C. Berks
- Centre for Metalloprotein Spectroscopy and Biology,
School of Biological Sciences and School of Chemical Sciences, University of East Anglia, Norwich NR4 7TJ and Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK Corresponding authors e-mail: or
| | - Andrew M. Hemmings
- Centre for Metalloprotein Spectroscopy and Biology,
School of Biological Sciences and School of Chemical Sciences, University of East Anglia, Norwich NR4 7TJ and Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK Corresponding authors e-mail: or
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27
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Taoka S, Banerjee R. Stopped-flow kinetic analysis of the reaction catalyzed by the full-length yeast cystathionine beta-synthase. J Biol Chem 2002; 277:22421-5. [PMID: 11948191 DOI: 10.1074/jbc.m202513200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cystathionine beta-synthase found in yeast catalyzes a pyridoxal phosphate-dependent condensation of homocysteine and serine to form cystathionine. Unlike the homologous mammalian enzymes, yeast cystathionine beta-synthase lacks a second cofactor, heme, which facilitates detailed kinetic studies of the enzyme because the different pyridoxal phosphate-bound intermediates can be followed by their characteristic absorption spectra. We conducted a rapid reaction kinetic analysis of the full-length yeast enzyme in the forward and reverse directions. In the forward direction, we observed formation of the external aldimine of serine (14 mm(-1) s(-1)) and the aminoacrylate intermediate (15 s(-1)). Homocysteine binds to the aminoacrylate with a bimolecular rate constant of 35 mm(-1) s(-1) and rapidly converts to cystathionine (180 s(-1)), leading to the accumulation of a 420 nm absorbing species, which has been assigned as the external aldimine of cystathionine. Release of cystathionine is slow (k = 2.3 s(-1)), which is similar to k(cat) (1.7 s(-1)) at 15 degrees C, consistent with this being a rate-determining step. In the reverse direction, cystathionine binds to the enzyme with a bimolecular rate constant of 1.5 mm(-1) s(-1) and is rapidly converted to the aminoacrylate without accumulation of the external aldimine. The kinetic behavior of the full-length enzyme shows notable differences from that reported for a truncated form of the enzyme lacking the C-terminal third of the protein (Jhee, K. H., Niks, D., McPhie, P., Dunn, M. F., and Miles, E. W. (2001) Biochemistry 40, 10873-10880).
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Affiliation(s)
- Shinichi Taoka
- Biochemistry Department, University of Nebraska, Lincoln, Nebraska 68588-0664, USA
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28
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Taoka S, Green EL, Loehr TM, Banerjee R. Mercuric chloride-induced spin or ligation state changes in ferric or ferrous human cystathionine beta-synthase inhibit enzyme activity. J Inorg Biochem 2001; 87:253-9. [PMID: 11744063 DOI: 10.1016/s0162-0134(01)00336-1] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Cystathionine beta-synthase is a key heme and pyridoxal phosphate-dependent enzyme involved in homocysteine metabolism in humans. The role of the recently discovered heme in this protein remains an important open question. The axial ligands to the heme in both the ferrous and ferric states have been assigned as cysteine and histidine residues, respectively. In this study, we have examined the effect of ligation and spin state changes in the heme on the activity of the enzyme. Treatment of the ferric enzyme with HgCl2 results in the conversion of six-coordinate low-spin heme to five-coordinate high-spin heme and is paralleled by a loss of activity. In contrast, treatment of the ferrous enzyme with HgCl2 results in replacement of the cysteine ligand by an unidentified sixth ligand and retention of the six-coordinate state, and is also accompanied by loss of enzyme activity. Treatment of the five-coordinate HgCl2-treated enzyme with thiols, such as homocysteine, results in reversion to a six-coordinate state. Resonance Raman spectroscopy with 34S-labeled enzyme reveals the return of the endogenous thiol ligand under these conditions and rules out direct coordination by the thiolate of homocysteine to the heme.
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Affiliation(s)
- S Taoka
- Department of Biochemistry, University of Nebraska, Lincoln, NE 68588-0664, USA
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29
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Taoka S, Banerjee R. Characterization of NO binding to human cystathionine beta-synthase: possible implications of the effects of CO and NO binding to the human enzyme. J Inorg Biochem 2001; 87:245-51. [PMID: 11744062 DOI: 10.1016/s0162-0134(01)00335-x] [Citation(s) in RCA: 155] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Homocysteine is a key junction metabolite that can be converted to cystathionine in a reaction catalyzed by the heme and pyridoxal phosphate-dependent cystathionine beta-synthase. The heme has unusual spectroscopic properties and the axial ligands have been assigned as histidine and cysteine, respectively. Its role in the protein is not obvious from the chemistry of the beta-replacement reaction that is catalyzed. We have characterized the binding of the gaseous signaling molecule, NO, to cystathionine beta-synthase and examined its effect on the reactions catalyzed by the truncated dimeric form of the enzyme, W409X, which is a natural variant. Binding of NO appears to result in the formation of a five-coordinate ferrous nitrosyl species in which both endogenous ligands have been lost. This is in contrast to CO binding which is reported to displace the thiolate ligand and form a six-coordinate species. NO binds to the full-length enzyme with a K(d) of 281+/-50 microM and to the truncated enzyme with a K(d) of 350+/-44 microM. Binding of NO to the full-length enzyme inhibits activity with a K(i) of 320+/-60 microM. These studies demonstrate that as with CO, perturbation of the heme environment by NO is communicated to the active site with concomitant inhibition of enzyme activity, and suggests a regulatory role for heme in cystathionine beta-synthase.
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Affiliation(s)
- S Taoka
- Department of Biochemistry, University of Nebraska, Lincoln, NE 68588-0664, USA
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Meier M, Janosik M, Kery V, Kraus JP, Burkhard P. Structure of human cystathionine beta-synthase: a unique pyridoxal 5'-phosphate-dependent heme protein. EMBO J 2001; 20:3910-6. [PMID: 11483494 PMCID: PMC149156 DOI: 10.1093/emboj/20.15.3910] [Citation(s) in RCA: 250] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2001] [Revised: 06/08/2001] [Accepted: 06/08/2001] [Indexed: 11/14/2022] Open
Abstract
Cystathionine beta-synthase (CBS) is a unique heme- containing enzyme that catalyzes a pyridoxal 5'-phosphate (PLP)-dependent condensation of serine and homocysteine to give cystathionine. Deficiency of CBS leads to homocystinuria, an inherited disease of sulfur metabolism characterized by increased levels of the toxic metabolite homocysteine. Here we present the X-ray crystal structure of a truncated form of the enzyme. CBS shares the same fold with O-acetylserine sulfhydrylase but it contains an additional N-terminal heme binding site. This heme binding motif together with a spatially adjacent oxidoreductase active site motif could explain the regulation of its enzyme activity by redox changes.
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Affiliation(s)
| | - Miroslav Janosik
- M.E.Müller Institute for Structural Biology, Biozentrum, University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland and
Departments of Pediatrics and Cellular and Structural Biology, University of Colorado School of Medicine, Denver, CO 80262, USA Corresponding author e-mail:
| | - Vladimir Kery
- M.E.Müller Institute for Structural Biology, Biozentrum, University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland and
Departments of Pediatrics and Cellular and Structural Biology, University of Colorado School of Medicine, Denver, CO 80262, USA Corresponding author e-mail:
| | - Jan P. Kraus
- M.E.Müller Institute for Structural Biology, Biozentrum, University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland and
Departments of Pediatrics and Cellular and Structural Biology, University of Colorado School of Medicine, Denver, CO 80262, USA Corresponding author e-mail:
| | - Peter Burkhard
- M.E.Müller Institute for Structural Biology, Biozentrum, University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland and
Departments of Pediatrics and Cellular and Structural Biology, University of Colorado School of Medicine, Denver, CO 80262, USA Corresponding author e-mail:
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Vadon-Le Goff S, Delaforge M, Boucher JL, Janosik M, Kraus JP, Mansuy D. Coordination chemistry of the heme in cystathionine beta-synthase: formation of iron(II)-isonitrile complexes. Biochem Biophys Res Commun 2001; 283:487-92. [PMID: 11327727 DOI: 10.1006/bbrc.2001.4807] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Interaction of rat and human cystathionine-beta-synthase (CBS) with various potential ligands has been studied by visible and EPR spectroscopy in order to explore the coordination chemistry of this atypical hemeprotein. Ferric CBS did not react with any classical hemeprotein ligands, such as various imidazole and pyridine derivatives, N(-)(3) and isonitriles RNC. Ferrous CBS also failed to bind these nitrogenous ligands or nitrosoalkanes. However, it reacts with various isonitriles RNC, leading to complexes characterized by a Soret peak at 433 +/- 2 nm. Binding of isonitriles to ferrous CBS is a relatively slow process; its rate markedly depends on the nature of R. It thus seems that the only exogenous ligands able to bind CBS iron are carbon-centered, very strong heme-Fe(II) ligands such as CNR, CO, and CN(-), presumably after dissociation of the CBS-iron(II)-cysteinate bond. Isonitriles appear as interesting tools for further studies on the topology of CBS active site.
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Affiliation(s)
- S Vadon-Le Goff
- Laboratoire de Chimie et Biochimie Pharmacologiques et Toxicologiques, UMR 8601 CNRS, Université Paris V, 45 Rue des Saints-Pères, Paris Cedex 06, 75270, France
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Metzler DE, Metzler CM, Sauke DJ. Coenzymes. Biochemistry 2001. [DOI: 10.1016/b978-012492543-4/50017-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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