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Wang Q, Aleshintsev A, Rai K, Jin E, Gupta R. Proton Transfer via Arginine with Suppressed p Ka Mediates Catalysis by Gentisate and Salicylate Dioxygenase. J Phys Chem B 2024. [PMID: 38978492 DOI: 10.1021/acs.jpcb.4c03164] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/10/2024]
Abstract
Gentisate and salicylate 1,2-dioxygenases (GDO and SDO) facilitate aerobic degradation of aromatic rings by inserting both atoms of dioxygen into their substrates, thereby participating in global carbon cycling. The role of acid-base catalysts in the reaction cycles of these enzymes is debatable. We present evidence of the participation of a proton shuffler during catalysis by GDO and SDO. The pH dependence of Michaelis-Menten parameters demonstrates that a single proton transfer is mandatory for the catalysis. Measurements at variable temperatures and pHs were used to determine the standard enthalpy of ionization (ΔHion°) of 51 kJ/mol for the proton transfer event. Although the observed apparent pKa in the range of 6.0-7.0 for substrates of both enzymes is highly suggestive of a histidine residue, ΔHion° establishes an arginine residue as the likely proton source, providing phylogenetic relevance for this strictly conserved residue in the GDO family. We propose that the atypical 3-histidine ferrous binding scaffold of GDOs contributes to the suppression of arginine pKa and provides support for this argument by employing a 2-histidine-1-carboxylate variant of the enzyme that exhibits elevated pKa. A reaction mechanism considering the role of the proton source in stabilizing key reaction intermediates is proposed.
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Affiliation(s)
- Qian Wang
- Department of Chemistry, College of Staten Island, City University of New York, Staten Island, New York 10314, United States
| | - Aleksey Aleshintsev
- Department of Chemistry, College of Staten Island, City University of New York, Staten Island, New York 10314, United States
- Ph.D. Programs in Biochemistry and Chemistry, The Graduate Center of the City University of New York, New York, New York 10016, United States
| | - Kamal Rai
- Department of Chemistry, College of Staten Island, City University of New York, Staten Island, New York 10314, United States
| | - Eric Jin
- Staten Island Technical High School, Staten Island, New York 10306, United States
| | - Rupal Gupta
- Department of Chemistry, College of Staten Island, City University of New York, Staten Island, New York 10314, United States
- Ph.D. Programs in Biochemistry and Chemistry, The Graduate Center of the City University of New York, New York, New York 10016, United States
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2
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Miller JR, Schnorrenberg EC, Aschenbrener C, Fox BG, Brunold TC. Kinetic and Spectroscopic Investigation of the Y157F and C93G/Y157F Variants of Cysteine Dioxygenase: Dissecting the Roles of the Second-Sphere Residues C93 and Y157. Biochemistry 2024; 63:1684-1696. [PMID: 38885352 PMCID: PMC11219262 DOI: 10.1021/acs.biochem.4c00177] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/20/2024]
Abstract
In mammals, l-cysteine (Cys) homeostasis is maintained by the mononuclear nonheme iron enzyme cysteine dioxygenase (CDO), which oxidizes Cys to cysteine sulfinic acid. CDO contains a rare post-translational modification, involving the formation of a thioether cross-link between a Cys residue at position 93 (Mus musculus CDO numbering) and a nearby tyrosine at position 157 (Cys-Tyr cross-link). As-isolated CDO contains both the cross-linked and non-cross-linked isoforms, and formation of the Cys-Tyr cross-link during repeated enzyme turnover increases CDO's catalytic efficiency by ∼10-fold. Interestingly, while the C93G CDO variant lacks the Cys-Tyr cross-link, it is similarly active as cross-linked wild-type (WT) CDO. Alternatively, the Y157F CDO variant, which also lacks the cross-link but maintains the free thiolate at position 93, exhibits a drastically reduced catalytic efficiency. These observations suggest that the untethered thiolate moiety of C93 is detrimental to CDO activity and/or that Y157 is essential for catalysis. To further assess the roles of residues C93 and Y157, we performed a spectroscopic and kinetic characterization of Y157F CDO and the newly designed C93G/Y157F CDO variant. Our results provide evidence that the non-cross-linked C93 thiolate stabilizes a water at the sixth coordination site of Cys-bound Y157F Fe(II)CDO. A water is also present, though more weakly coordinated, in Cys-bound C93G/Y157F Fe(II)CDO. The presence of a water molecule, which must be displaced by cosubstrate O2, likely makes a significant contribution to the ∼15-fold and ∼7-fold reduced catalytic efficiencies of the Y157F and C93G/Y157F CDO variants, respectively, relative to cross-linked WT CDO.
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Affiliation(s)
- Joshua R. Miller
- Department of Chemistry, University of Wisconsin – Madison, Madison, Wisconsin 53706, United States
| | | | - Cole Aschenbrener
- Department of Chemistry, University of Wisconsin – Madison, Madison, Wisconsin 53706, United States
| | - Brian G. Fox
- Department of Biochemistry, University of Wisconsin – Madison, Madison, Wisconsin 53706, United States
| | - Thomas C. Brunold
- Department of Chemistry, University of Wisconsin – Madison, Madison, Wisconsin 53706, United States
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3
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Wang Q, Li H, Bujupi U, Gröning J, Stolz A, Bongiorno A, Gupta R. Oxygen Activation in Aromatic Ring Cleaving Salicylate Dioxygenase: Detection of Reaction Intermediates with a Nitro-substituted Substrate Analog. Chembiochem 2024; 25:e202400023. [PMID: 38363551 DOI: 10.1002/cbic.202400023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2024] [Revised: 02/15/2024] [Accepted: 02/16/2024] [Indexed: 02/17/2024]
Abstract
Cupin dioxygenases such as salicylate 1,2-dioxygense (SDO) perform aromatic C-C bond scission via a 3-His motif tethered iron cofactor. Here, transient kinetics measurements are used to monitor the catalytic cycle of SDO by using a nitro-substituted substrate analog, 3-nitrogentisate. Compared to the natural substrate, the nitro group reduces the enzymatic kcat by 500-fold, thereby facilitating the detection and kinetic characterization of reaction intermediates. Sums and products of reciprocal relaxation times derived from kinetic measurements were found to be linearly dependent on O2 concentration, suggesting reversible formation of two distinct intermediates. Dioxygen binding to the metal cofactor takes place with a forward rate of 5.9×103 M-1 s-1: two orders of magnitude slower than other comparable ring-cleaving dioxygenses. Optical chromophore of the first intermediate is distinct from the in situ generated SDO Fe(III)-O2⋅- complex but closer to the enzyme-substrate precursor.
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Affiliation(s)
- Qian Wang
- Department of Chemistry, College of Staten Island, The City University of New York, 2800 Victory Blvd. Staten Island, New York, 10314, United States
| | - Hanbin Li
- Department of Chemistry, College of Staten Island, The City University of New York, 2800 Victory Blvd. Staten Island, New York, 10314, United States
- Ph.D. Programs in Chemistry and Physics, The Graduate Center of the City University of New York, New York, 10016, United States
| | - Uran Bujupi
- Department of Chemistry, College of Staten Island, The City University of New York, 2800 Victory Blvd. Staten Island, New York, 10314, United States
| | - Janosch Gröning
- Institut für Mikrobiologie, Universität Stuttgart, Allmandring 31, 70569, Stuttgart, Germany
| | - Andreas Stolz
- Institut für Mikrobiologie, Universität Stuttgart, Allmandring 31, 70569, Stuttgart, Germany
| | - Angelo Bongiorno
- Department of Chemistry, College of Staten Island, The City University of New York, 2800 Victory Blvd. Staten Island, New York, 10314, United States
- Ph.D. Programs in Chemistry and Physics, The Graduate Center of the City University of New York, New York, 10016, United States
| | - Rupal Gupta
- Department of Chemistry, College of Staten Island, The City University of New York, 2800 Victory Blvd. Staten Island, New York, 10314, United States
- Ph.D. Programs in Biochemistry, The Graduate Center of the City University of New York, New York, 10016, United States
- Ph.D. Programs in Chemistry and Physics, The Graduate Center of the City University of New York, New York, 10016, United States
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4
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Gao Y, Zhu Y, Awakawa T, Abe I. Unusual cysteine modifications in natural product biosynthesis. RSC Chem Biol 2024; 5:293-311. [PMID: 38576726 PMCID: PMC10989515 DOI: 10.1039/d4cb00020j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2024] [Accepted: 02/08/2024] [Indexed: 04/06/2024] Open
Abstract
l-Cysteine is a highly reactive amino acid that is modified into a variety of chemical structures, including cysteine sulfinic acid in human metabolic pathways, and sulfur-containing scaffolds of amino acids, alkaloids, and peptides in natural product biosynthesis. Among the modification enzymes responsible for these cysteine-derived compounds, metalloenzymes constitute an important family of enzymes that catalyze a wide variety of reactions. Therefore, understanding their reaction mechanisms is important for the biosynthetic production of cysteine-derived natural products. This review mainly summarizes recent mechanistic investigations of metalloenzymes, with a particular focus on recently discovered mononuclear non-heme iron (NHI) enzymes, dinuclear NHI enzymes, and radical-SAM enzymes involved in unusual cysteine modifications in natural product biosynthesis.
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Affiliation(s)
- Yaojie Gao
- Graduate School of Pharmaceutical Sciences, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku Tokyo 113-0033 Japan
| | - Yuhao Zhu
- Graduate School of Pharmaceutical Sciences, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku Tokyo 113-0033 Japan
| | - Takayoshi Awakawa
- Graduate School of Pharmaceutical Sciences, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku Tokyo 113-0033 Japan
- RIKEN Center for Sustainable Resource Science Wako Saitama 351-0198 Japan
| | - Ikuro Abe
- Graduate School of Pharmaceutical Sciences, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku Tokyo 113-0033 Japan
- Collaborative Research Institute for Innovative Microbiology, The University of Tokyo Yayoi 1-1-1, Bunkyo-ku Tokyo 113-8657 Japan
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5
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Pierce BS, Schmittou AN, York NJ, Madigan RP, Nino PF, Foss FW, Lockart MM. Improved resolution of 3-mercaptopropionate dioxygenase active site provided by ENDOR spectroscopy offers insight into catalytic mechanism. J Biol Chem 2024; 300:105777. [PMID: 38395308 PMCID: PMC10966181 DOI: 10.1016/j.jbc.2024.105777] [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: 11/28/2023] [Revised: 02/13/2024] [Accepted: 02/15/2024] [Indexed: 02/25/2024] Open
Abstract
3-mercaptopropionate (3MPA) dioxygenase (MDO) is a mononuclear nonheme iron enzyme that catalyzes the O2-dependent oxidation of thiol-bearing substrates to yield the corresponding sulfinic acid. MDO is a member of the cysteine dioxygenase family of small molecule thiol dioxygenases and thus shares a conserved sequence of active site residues (Serine-155, Histidine-157, and Tyrosine-159), collectively referred to as the SHY-motif. It has been demonstrated that these amino acids directly interact with the mononuclear Fe-site, influencing steady-state catalysis, catalytic efficiency, O2-binding, and substrate coordination. However, the underlying mechanism by which this is accomplished is poorly understood. Here, pulsed electron paramagnetic resonance spectroscopy [1H Mims electron nuclear double resonance spectroscopy] is applied to validate density functional theory computational models for the MDO Fe-site simultaneously coordinated by substrate and nitric oxide (NO), (3MPA/NO)-MDO. The enhanced resolution provided by electron nuclear double resonance spectroscopy allows for direct observation of Fe-bound substrate conformations and H-bond donation from Tyr159 to the Fe-bound NO ligand. Further inclusion of SHY-motif residues within the validated model reveals a distinct channel restricting movement of the Fe-bound NO-ligand. It has been argued that the iron-nitrosyl emulates the structure of potential Fe(III)-superoxide intermediates within the MDO catalytic cycle. While the merit of this assumption remains unconfirmed, the model reported here offers a framework to evaluate oxygen binding at the substrate-bound Fe-site and possible reaction mechanisms. It also underscores the significance of hydrogen bonding interactions within the enzymatic active site.
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Affiliation(s)
- Brad S Pierce
- Department of Chemistry & Biochemistry, University of Alabama, Tuscaloosa, Alabama, USA.
| | - Allison N Schmittou
- Department of Chemistry & Biochemistry, University of Alabama, Tuscaloosa, Alabama, USA
| | - Nicholas J York
- Department of Chemistry & Biochemistry, University of Alabama, Tuscaloosa, Alabama, USA
| | - Ryan P Madigan
- Department of Chemistry & Biochemistry, The University of Texas at Arlington, Arlington, Texas, USA
| | - Paula F Nino
- Department of Chemistry & Biochemistry, The University of Texas at Arlington, Arlington, Texas, USA
| | - Frank W Foss
- Department of Chemistry & Biochemistry, The University of Texas at Arlington, Arlington, Texas, USA
| | - Molly M Lockart
- Department of Chemistry and Biochemistry, Samford University, Homewood, Alabama, USA.
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6
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York NJ, Lockart MM, Schmittou AN, Pierce BS. Cyanide replaces substrate in obligate-ordered addition of nitric oxide to the non-heme mononuclear iron AvMDO active site. J Biol Inorg Chem 2023; 28:285-299. [PMID: 36809458 PMCID: PMC10075186 DOI: 10.1007/s00775-023-01990-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Accepted: 01/12/2023] [Indexed: 02/23/2023]
Abstract
Thiol dioxygenases are a subset of non-heme mononuclear iron oxygenases that catalyze the O2-dependent oxidation of thiol-bearing substrates to yield sulfinic acid products. Cysteine dioxygenase (CDO) and 3-mercaptopropionic acid (3MPA) dioxygenase (MDO) are the most extensively characterized members of this enzyme family. As with many non-heme mononuclear iron oxidase/oxygenases, CDO and MDO exhibit an obligate-ordered addition of organic substrate before dioxygen. As this substrate-gated O2-reactivity extends to the oxygen-surrogate, nitric oxide (NO), EPR spectroscopy has long been used to interrogate the [substrate:NO:enzyme] ternary complex. In principle, these studies can be extrapolated to provide information about transient iron-oxo intermediates produced during catalytic turnover with dioxygen. In this work, we demonstrate that cyanide mimics the native thiol-substrate in ordered-addition experiments with MDO cloned from Azotobacter vinelandii (AvMDO). Following treatment of the catalytically active Fe(II)-AvMDO with excess cyanide, addition of NO yields a low-spin (S = 1/2) (CN/NO)-Fe-complex. Continuous wave and pulsed X-band EPR characterization of this complex produced in wild-type and H157N variant AvMDO reveal multiple nuclear hyperfine features diagnostic of interactions within the first- and outer-coordination sphere of the enzymatic Fe-site. Spectroscopically validated computational models indicate simultaneous coordination of two cyanide ligands replaces the bidentate (thiol and carboxylate) coordination of 3MPA allowing for NO-binding at the catalytically relevant O2-binding site. This promiscuous substrate-gated reactivity of AvMDO with NO provides an instructive counterpoint to the high substrate-specificity exhibited by mammalian CDO for L-cysteine.
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Affiliation(s)
- Nicholas J York
- Department of Chemistry and Biochemistry, University of Alabama, 250 Hackberry Lane, Tuscaloosa, AL, 35487, USA
| | - Molly M Lockart
- Department of Chemistry and Biochemistry, Samford University, 800 Lakeshore Drive, Homewood, AL, 35229, USA
| | - Allison N Schmittou
- Department of Chemistry and Biochemistry, University of Alabama, 250 Hackberry Lane, Tuscaloosa, AL, 35487, USA
| | - Brad S Pierce
- Department of Chemistry and Biochemistry, University of Alabama, 250 Hackberry Lane, Tuscaloosa, AL, 35487, USA.
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7
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Miller JR, Brunold TC. Spectroscopic analysis of the mammalian enzyme cysteine dioxygenase. Methods Enzymol 2023; 682:101-135. [PMID: 36948699 PMCID: PMC11230041 DOI: 10.1016/bs.mie.2023.01.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
Abstract
l-Cysteine (Cys) is an essential building block for the synthesis of new proteins and serves as a precursor for several biologically important sulfur-containing molecules, such as coenzyme A, taurine, glutathione, and inorganic sulfate. However, organisms must tightly regulate the concentration of free Cys, as elevated levels of this semi-essential amino acid can be extremely harmful. The non-heme iron enzyme cysteine dioxygenase (CDO) serves to maintain the proper levels of Cys by catalyzing its oxidation to cysteine sulfinic acid. Crystal structures of resting and substrate-bound mammalian CDO revealed two surprising structural motifs in the first and second coordination spheres of the Fe center. The first is the existence of a neutral three histidine (3-His) facial triad that coordinates the Fe ion, as opposed to an anionic 2-His-1-carboxylate facial triad that is typically observed in mononuclear non-heme Fe(II) dioxygenases. The second unusual structural feature exhibited by mammalian CDO is the presence of a covalent crosslink between the sulfur of a Cys residue and an ortho-carbon of a tyrosine residue. Spectroscopic studies of CDO have provided invaluable insights into the roles that these unusual features play with regards to substrate Cys and co-substrate O2 binding and activation. In this chapter, we summarize results obtained from electronic absorption, electron paramagnetic resonance, magnetic circular dichroism, resonance Raman, and Mössbauer spectroscopic studies of mammalian CDO carried out in the last two decades. Pertinent results obtained from complementary computational studies are also briefly summarized.
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Affiliation(s)
- Joshua R Miller
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, United States
| | - Thomas C Brunold
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, United States.
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8
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Albert T, Moënne-Loccoz P. Spectroscopic Characterization of a Diferric Mycobacterial Hemerythrin-Like Protein with Unprecedented Reactivity toward Nitric Oxide. J Am Chem Soc 2022; 144:17611-17621. [PMID: 36099449 DOI: 10.1021/jacs.2c07113] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Hemerythrin-like proteins (HLPs) are broadly distributed across taxonomic groups and appear to play highly diverse functional roles in prokaryotes. Mycobacterial HLPs contribute to the survival of these pathogenic bacteria in mammalian macrophages, but their modes of action remain unclear. A recent crystallographic characterization of Mycobacterium kansasii HLP (Mka-HLP) revealed the unexpected presence of a tyrosine sidechain (Tyr54) near the coordination sphere of one of the two iron centers. Here, we show that Tyr54 is a true ligand to the Fe2(III) ion which, in conjunction with the presence of a μ-oxo group bridging the two iron(III), brings unique reactivity toward nitric oxide (NO). Monitoring the titration of Mka-HLP with NO by Fourier-transform infrared and electron paramagnetic resonance spectroscopies shows that both diferric and diferrous forms of Mka-HLP accumulate an uncoupled high-spin and low-spin {FeNO}7 pair. We assign the reactivity of the diferric protein to an initial radical reaction between NO and the μ-oxo bridge to form nitrite and a mixed-valent diiron center that can react further with NO. Amperometric measurements of NO consumption by Mka-HLP confirm that this reactivity can proceed at low micromolar concentrations of NO, before additional NO consumption, supporting a NO scavenging role for mycobacterial HLPs.
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Affiliation(s)
- Therese Albert
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, Oregon 97239, United States
| | - Pierre Moënne-Loccoz
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, Oregon 97239, United States
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9
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Fernandez RL, Juntunen ND, Brunold TC. Differences in the Second Coordination Sphere Tailor the Substrate Specificity and Reactivity of Thiol Dioxygenases. Acc Chem Res 2022; 55:2480-2490. [PMID: 35994511 PMCID: PMC9583696 DOI: 10.1021/acs.accounts.2c00359] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
In recent years, considerable progress has been made toward elucidating the geometric and electronic structures of thiol dioxygenases (TDOs). TDOs catalyze the conversion of substrates with a sulfhydryl group to their sulfinic acid derivatives via the addition of both oxygen atoms from molecular oxygen. All TDOs discovered to date belong to the family of cupin-type mononuclear nonheme Fe(II)-dependent metalloenzymes. While most members of this enzyme family bind the Fe cofactor by two histidines and one carboxylate side chain (2-His-1-carboxylate) to provide a monoanionic binding motif, TDOs feature a neutral three histidine (3-His) facial triad. In this Account, we present a bioinformatics analysis and multiple sequence alignment that highlight the significance of the secondary coordination sphere in tailoring the substrate specificity and reactivity among the different TDOs. These insights provide the framework within which important structural and functional features of the distinct TDOs are discussed.The best studied TDO is cysteine dioxygenase (CDO), which catalyzes the conversion of cysteine to cysteine sulfinic acid in both eukaryotes and prokaryotes. Crystal structures of resting and substrate-bound mammalian CDOs revealed two surprising structural motifs in the first- and second coordination spheres of the Fe center. The first is the presence of the abovementioned neutral 3-His facial triad that coordinates the Fe ion. The second is the existence of a covalent cross-link between the sulfur of Cys93 and an ortho carbon of Tyr157 (mouse CDO numbering scheme). While the exact role of this cross-link remains incompletely understood, various studies established that it is needed for proper substrate Cys positioning and gating solvent access to the active site. Intriguingly, bacterial CDOs lack the Cys-Tyr cross-link; yet, they are as active as cross-linked eukaryotic CDOs.The other known mammalian TDO is cysteamine dioxygenase (ADO). Initially, it was believed that ADO solely catalyzes the oxidation of cysteamine to hypotaurine. However, it has recently been shown that ADO additionally oxidizes N-terminal cysteine (Nt-Cys) peptides, which indicates that ADO may play a much more significant role in mammalian physiology than was originally anticipated. Though predicted on the basis of sequence alignment, site-directed mutagenesis, and spectroscopic studies, it was not until last year that two crystal structures, one of wild-type mouse ADO (solved by us) and the other of a variant of nickel-substituted human ADO, finally provided direct evidence that this enzyme also features a 3-His facial triad. These structures additionally revealed several features that are unique to ADO, including a putative cosubstrate O2 access tunnel that is lined by two Cys residues. Disulfide formation under conditions of high O2 levels may serve as a gating mechanism to prevent ADO from depleting organisms of Nt-Cys-containing molecules.The combination of kinetic and spectroscopic studies in conjunction with structural characterizations of TDOs has furthered our understanding of enzymatic sulfhydryl substrate regulation. In this article, we take advantage of the fact that the ADO X-ray crystal structures provided the final piece needed to compare and contrast key features of TDOs, an essential family of metalloenzymes found across all kingdoms of life.
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Affiliation(s)
- Rebeca L. Fernandez
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Nicholas D. Juntunen
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Thomas C. Brunold
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
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10
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Cheng R, Weitz AC, Paris J, Tang Y, Zhang J, Song H, Naowarojna N, Li K, Qiao L, Lopez J, Grinstaff MW, Zhang L, Guo Y, Elliott S, Liu P. OvoA Mtht from Methyloversatilis thermotolerans ovothiol biosynthesis is a bifunction enzyme: thiol oxygenase and sulfoxide synthase activities. Chem Sci 2022; 13:3589-3598. [PMID: 35432880 PMCID: PMC8943887 DOI: 10.1039/d1sc05479a] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2021] [Accepted: 02/24/2022] [Indexed: 01/03/2023] Open
Abstract
Mononuclear non-heme iron enzymes are a large class of enzymes catalyzing a wide-range of reactions. In this work, we report that a non-heme iron enzyme in Methyloversatilis thermotolerans, OvoAMtht, has two different activities, as a thiol oxygenase and a sulfoxide synthase. When cysteine is presented as the only substrate, OvoAMtht is a thiol oxygenase. In the presence of both histidine and cysteine as substrates, OvoAMtht catalyzes the oxidative coupling between histidine and cysteine (a sulfoxide synthase). Additionally, we demonstrate that both substrates and the active site iron's secondary coordination shell residues exert exquisite control over the dual activities of OvoAMtht (sulfoxide synthase vs. thiol oxygenase activities). OvoAMtht is an excellent system for future detailed mechanistic investigation on how metal ligands and secondary coordination shell residues fine-tune the iron-center electronic properties to achieve different reactivities. Modulation of OvoAMtht's dual activities: sulfoxide synthase and thiol oxygenase.![]()
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Affiliation(s)
- Ronghai Cheng
- Department of Chemistry, Boston University 590 Commonwealth Ave. Boston MA 02215 USA
| | - Andrew C Weitz
- Department of Chemistry, Boston University 590 Commonwealth Ave. Boston MA 02215 USA
| | - Jared Paris
- Department of Chemistry, Carnegie Mellon University 4400 Fifth Avenue Pittsburgh PA 1521 USA
| | - Yijie Tang
- Department of Chemistry, Carnegie Mellon University 4400 Fifth Avenue Pittsburgh PA 1521 USA
| | - Jingyu Zhang
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology 130 Meilong Rd Shanghai 200237 China
| | - Heng Song
- Department of Chemistry, Boston University 590 Commonwealth Ave. Boston MA 02215 USA
| | - Nathchar Naowarojna
- Department of Chemistry, Boston University 590 Commonwealth Ave. Boston MA 02215 USA
| | - Kelin Li
- Department of Chemistry, Boston University 590 Commonwealth Ave. Boston MA 02215 USA
| | - Lu Qiao
- Department of Chemistry, Boston University 590 Commonwealth Ave. Boston MA 02215 USA
| | - Juan Lopez
- Department of Chemistry, Boston University 590 Commonwealth Ave. Boston MA 02215 USA
| | - Mark W Grinstaff
- Department of Chemistry, Boston University 590 Commonwealth Ave. Boston MA 02215 USA
| | - Lixin Zhang
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology 130 Meilong Rd Shanghai 200237 China
| | - Yisong Guo
- Department of Chemistry, Carnegie Mellon University 4400 Fifth Avenue Pittsburgh PA 1521 USA
| | - Sean Elliott
- Department of Chemistry, Boston University 590 Commonwealth Ave. Boston MA 02215 USA
| | - Pinghua Liu
- Department of Chemistry, Boston University 590 Commonwealth Ave. Boston MA 02215 USA
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11
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York NJ, Lockart MM, Pierce BS. Low-Spin Cyanide Complexes of 3-Mercaptopropionic Acid Dioxygenase (MDO) Reveal the Impact of Outer-Sphere SHY-Motif Residues. Inorg Chem 2021; 60:18639-18651. [PMID: 34883020 PMCID: PMC10078988 DOI: 10.1021/acs.inorgchem.1c01519] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
3-Mercaptopropionic acid (3MPA) dioxygenase (MDO) is a non-heme Fe(II)/O2-dependent oxygenase that catalyzes the oxidation of thiol-substrates to yield the corresponding sulfinic acid. Hydrogen-bonding interactions between the Fe-site and a conserved set of three outer-sphere residues (Ser-His-Tyr) play an important catalytic role in the mechanism of this enzyme. Collectively referred to as the SHY-motif, the functional role of these residues remains poorly understood. Here, catalytically inactive Fe(III)-MDO precomplexed with 3MPA was titrated with cyanide to yield a low-spin (S = 1/2) (3MPA/CN)-bound ternary complex (referred to as 1C). UV-visible and electron paramagnetic resonance (EPR) spectroscopy were used to monitor the binding of 3MPA and cyanide. Comparisons of results obtained from SHY-motif variants (H157N and Y159F) were performed to investigate specific H-bonding interactions. For the wild-type enzyme, the binding of 3MPA- and cyanide to the enzymatic Fe-site is selective and results in a homogeneous ternary complex. However, this selectivity is lost for the Y159F variant, suggesting that H-bonding interactions contributed from Tyr159 gate ligand coordination at the Fe-site. Significantly, the g-values for the low-spin ferric site are diagnostic of the directionality of Tyr159 H-bond donation. Computational models coupled with CASSCF/NEVPT2-calculated g-values were used to verify that a major shift in the central g-value (g2) displayed between wild-type and SHY variants could be attributed to the loss of Tyr159 H-bond donation to the Fe-bound cyanide. Applied to native cosubstrate, this H-bond donation provides a means to stabilize Fe-bound dioxygen and potentially explains the attenuated (∼15-fold) rate of catalytic turnover previously reported for MDO SHY-motif variants.
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Affiliation(s)
- Nicholas J York
- Department of Chemistry & Biochemistry, University of Alabama, 250 Hackberry Lane, Tuscaloosa, Alabama 35487, United States
| | - Molly M Lockart
- Department of Chemistry & Biochemistry, University of Alabama, 250 Hackberry Lane, Tuscaloosa, Alabama 35487, United States
| | - Brad S Pierce
- Department of Chemistry & Biochemistry, University of Alabama, 250 Hackberry Lane, Tuscaloosa, Alabama 35487, United States
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12
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Fernandez RL, Juntunen ND, Fox BG, Brunold TC. Spectroscopic investigation of iron(III) cysteamine dioxygenase in the presence of substrate (analogs): implications for the nature of substrate-bound reaction intermediates. J Biol Inorg Chem 2021; 26:947-955. [PMID: 34580769 PMCID: PMC8643075 DOI: 10.1007/s00775-021-01904-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Accepted: 09/08/2021] [Indexed: 12/15/2022]
Abstract
Thiol dioxygenases (TDOs) are a class of metalloenzymes that oxidize various thiol-containing substrates to their corresponding sulfinic acids. Originally established by X-ray crystallography for cysteine dioxygenase (CDO), all TDOs are believed to contain a 3-histidine facial triad that coordinates the necessary Fe(II) cofactor. However, very little additional information is available for cysteamine dioxygenase (ADO), the only other mammalian TDO besides CDO. Previous spectroscopic characterizations revealed that ADO likely binds substrate cysteamine in a monodentate fashion, while a mass spectrometry study provided evidence that a thioether crosslink can form between Cys206 and Tyr208 (mouse ADO numbering). In the present study, we have used electronic absorption and electron paramagnetic resonance (EPR) spectroscopies to investigate the species formed upon incubation of Fe(III)ADO with sulfhydryl-containing substrates and the superoxide surrogates azide and cyanide. Our data reveal that azide is unable to coordinate to cysteamine-bound Fe(III)ADO, suggesting that the Fe(III) center lacks an open coordination site or azide competes with cysteamine for the same binding site. Alternatively, cyanide binds to either cysteamine- or Cys-bound Fe(III)ADO to yield a low-spin (S = 1/2) EPR signal that is distinct from that observed for cyanide/Cys-bound Fe(III)CDO, revealing differences in the active-site pockets between ADO and CDO. Finally, EPR spectra obtained for cyanide/cysteamine adducts of wild-type Fe(III)ADO and its Tyr208Phe variant are superimposable, implying that either an insignificant fraction of as-isolated wild-type enzyme is crosslinked or that formation of the thioether bond has minimal effects on the electronic structure of the iron cofactor.
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Affiliation(s)
- Rebeca L Fernandez
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Nicholas D Juntunen
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Brian G Fox
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Thomas C Brunold
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, 53706, USA.
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13
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Gunawardana DM, Heathcote KC, Flashman E. Emerging roles for thiol dioxygenases as oxygen sensors. FEBS J 2021; 289:5426-5439. [PMID: 34346181 DOI: 10.1111/febs.16147] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Revised: 07/21/2021] [Accepted: 08/03/2021] [Indexed: 12/22/2022]
Abstract
Cysteine dioxygenases, 3-mercaptopropionate dioxygenases and mercaptosuccinate dioxygenases are all thiol dioxygenases (TDOs) that catalyse oxidation of thiol molecules to sulphinates. They are Fe(II)-dependent dioxygenases with a cupin fold that supports a 3xHis metal-coordinating triad at the active site. They also have other, broadly common features including arginine residues involved in substrate carboxylate binding and a conserved trio of residues at the active site featuring a tyrosine important in substrate binding catalysis. Recently, N-terminal cysteinyl dioxygenase enzymes (NCOs) have been identified in plants (plant cysteine oxidases, PCOs), while human 2-aminoethanethiol dioxygenase (ADO) has been shown to act as both an NCO and a small molecule TDO. Although the cupin fold and 3xHis Fe(II)-binding triad seen in the small molecule TDOs are conserved in NCOs, other active site features and aspects of the overall protein architecture are quite different. Furthermore, the PCOs and ADO appear to act as biological O2 sensors, as shown by kinetic analyses and hypoxic regulation of the stability of their biological targets (N-terminal cysteine oxidation triggers protein degradation via the N-degron pathway). Here, we discuss the emergence of these two subclasses of TDO including structural features that could dictate their ability to bind small molecule or polypeptide substrates. These structural features may also underpin the O2 -sensing capability of the NCOs. Understanding how these enzymes interact with their substrates, including O2 , could reveal strategies to manipulate their activity, relevant to hypoxic disease states and plant adaptive responses to flooding.
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14
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Tian S, Fan R, Albert T, Khade RL, Dai H, Harnden KA, Hosseinzadeh P, Liu J, Nilges MJ, Zhang Y, Moënne-Loccoz P, Guo Y, Lu Y. Stepwise nitrosylation of the nonheme iron site in an engineered azurin and a molecular basis for nitric oxide signaling mediated by nonheme iron proteins. Chem Sci 2021; 12:6569-6579. [PMID: 34040732 PMCID: PMC8132939 DOI: 10.1039/d1sc00364j] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Mononitrosyl and dinitrosyl iron species, such as {FeNO}7, {FeNO}8 and {Fe(NO)2}9, have been proposed to play pivotal roles in the nitrosylation processes of nonheme iron centers in biological systems. Despite their importance, it has been difficult to capture and characterize them in the same scaffold of either native enzymes or their synthetic analogs due to the distinct structural requirements of the three species, using redox reagents compatible with biomolecules under physiological conditions. Here, we report the realization of stepwise nitrosylation of a mononuclear nonheme iron site in an engineered azurin under such conditions. Through tuning the number of nitric oxide equivalents and reaction time, controlled formation of {FeNO}7 and {Fe(NO)2}9 species was achieved, and the elusive {FeNO}8 species was inferred by EPR spectroscopy and observed by Mössbauer spectroscopy, with complemental evidence for the conversion of {FeNO}7 to {Fe(NO)2}9 species by UV-Vis, resonance Raman and FT-IR spectroscopies. The entire pathway of the nitrosylation process, Fe(ii) → {FeNO}7 → {FeNO}8 → {Fe(NO)2}9, has been elucidated within the same protein scaffold based on spectroscopic characterization and DFT calculations. These results not only enhance the understanding of the dinitrosyl iron complex formation process, but also shed light on the physiological roles of nitric oxide signaling mediated by nonheme iron proteins. Stepwise nitrosylation from Fe(ii) to {FeNO}7, {FeNO}8 and then to {Fe(NO)2}9 is reported for the first time in the same protein scaffold, providing deeper understanding of the detailed mechanism of dinitrosyl iron complex formation.![]()
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Affiliation(s)
- Shiliang Tian
- Department of Chemistry, Department of Biochemistry, School of Chemical Sciences Electron Paramagnetic Resonance Lab, University of Illinois at Urbana-Champaign 600 South Mathews Avenue Urbana IL USA +1-217-333-2619
| | - Ruixi Fan
- Department of Chemistry, Carnegie Mellon University 4400 Fifth Avenue Pittsburgh PA USA +1-412-268-1061 +1-412-268-1704
| | - Therese Albert
- Department of Chemical Physiology and Biochemistry, Oregon Health & Science University 3181 S.W. Sam Jackson Park Road Portland OR USA +1-503-346-3429
| | - Rahul L Khade
- Department of Chemistry and Chemical Biology, Stevens Institute of Technology 1 Castle Point Terrace Hoboken NJ USA +1-201-216-8240 +1-201-216-5513
| | - Huiguang Dai
- Department of Chemistry, Department of Biochemistry, School of Chemical Sciences Electron Paramagnetic Resonance Lab, University of Illinois at Urbana-Champaign 600 South Mathews Avenue Urbana IL USA +1-217-333-2619
| | - Kevin A Harnden
- Department of Chemistry, Department of Biochemistry, School of Chemical Sciences Electron Paramagnetic Resonance Lab, University of Illinois at Urbana-Champaign 600 South Mathews Avenue Urbana IL USA +1-217-333-2619
| | - Parisa Hosseinzadeh
- Department of Chemistry, Department of Biochemistry, School of Chemical Sciences Electron Paramagnetic Resonance Lab, University of Illinois at Urbana-Champaign 600 South Mathews Avenue Urbana IL USA +1-217-333-2619
| | - Jing Liu
- Department of Chemistry, Department of Biochemistry, School of Chemical Sciences Electron Paramagnetic Resonance Lab, University of Illinois at Urbana-Champaign 600 South Mathews Avenue Urbana IL USA +1-217-333-2619
| | - Mark J Nilges
- Department of Chemistry, Department of Biochemistry, School of Chemical Sciences Electron Paramagnetic Resonance Lab, University of Illinois at Urbana-Champaign 600 South Mathews Avenue Urbana IL USA +1-217-333-2619
| | - Yong Zhang
- Department of Chemistry and Chemical Biology, Stevens Institute of Technology 1 Castle Point Terrace Hoboken NJ USA +1-201-216-8240 +1-201-216-5513
| | - Pierre Moënne-Loccoz
- Department of Chemical Physiology and Biochemistry, Oregon Health & Science University 3181 S.W. Sam Jackson Park Road Portland OR USA +1-503-346-3429
| | - Yisong Guo
- Department of Chemistry, Carnegie Mellon University 4400 Fifth Avenue Pittsburgh PA USA +1-412-268-1061 +1-412-268-1704
| | - Yi Lu
- Department of Chemistry, Department of Biochemistry, School of Chemical Sciences Electron Paramagnetic Resonance Lab, University of Illinois at Urbana-Champaign 600 South Mathews Avenue Urbana IL USA +1-217-333-2619
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15
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York NJ, Lockart MM, Sardar S, Khadka N, Shi W, Stenkamp RE, Zhang J, Kiser PD, Pierce BS. Structure of 3-mercaptopropionic acid dioxygenase with a substrate analog reveals bidentate substrate binding at the iron center. J Biol Chem 2021; 296:100492. [PMID: 33662397 PMCID: PMC8050391 DOI: 10.1016/j.jbc.2021.100492] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Revised: 02/18/2021] [Accepted: 02/26/2021] [Indexed: 12/20/2022] Open
Abstract
Thiol dioxygenases are a subset of nonheme iron oxygenases that catalyze the formation of sulfinic acids from sulfhydryl-containing substrates and dioxygen. Among this class, cysteine dioxygenases (CDOs) and 3-mercaptopropionic acid dioxygenases (3MDOs) are the best characterized, and the mode of substrate binding for CDOs is well understood. However, the manner in which 3-mercaptopropionic acid (3MPA) coordinates to the nonheme iron site in 3MDO remains a matter of debate. A model for bidentate 3MPA coordination at the 3MDO Fe-site has been proposed on the basis of computational docking, whereas steady-state kinetics and EPR spectroscopic measurements suggest a thiolate-only coordination of the substrate. To address this gap in knowledge, we determined the structure of Azobacter vinelandii 3MDO (Av3MDO) in complex with the substrate analog and competitive inhibitor, 3-hydroxypropionic acid (3HPA). The structure together with DFT computational modeling demonstrates that 3HPA and 3MPA associate with iron as chelate complexes with the substrate-carboxylate group forming an additional interaction with Arg168 and the thiol bound at the same position as in CDO. A chloride ligand was bound to iron in the coordination site assigned as the O2-binding site. Supporting HYSCORE spectroscopic experiments were performed on the (3MPA/NO)-bound Av3MDO iron nitrosyl (S = 3/2) site. In combination with spectroscopic simulations and optimized DFT models, this work provides an experimentally verified model of the Av3MDO enzyme-substrate complex, effectively resolving a debate in the literature regarding the preferred substrate-binding denticity. These results elegantly explain the observed 3MDO substrate specificity, but leave unanswered questions regarding the mechanism of substrate-gated reactivity with dioxygen.
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Affiliation(s)
- Nicholas J York
- Department of Chemistry & Biochemistry, University of Alabama, Tuscaloosa, Alabama, USA
| | - Molly M Lockart
- Department of Chemistry & Biochemistry, University of Alabama, Tuscaloosa, Alabama, USA
| | - Sinjinee Sardar
- Department of Chemistry & Biochemistry, The University of Texas at Arlington, Arlington, Texas, USA
| | - Nimesh Khadka
- Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio, USA
| | - Wuxian Shi
- National Synchrotron Light Source-II, Brookhaven National Laboratory, Upton, New York, USA
| | - Ronald E Stenkamp
- Departments of Biological Structure and Biochemistry, University of Washington, Seattle, Washington, USA
| | - Jianye Zhang
- Department of Ophthalmology, School of Medicine, University of California, Irvine, Irvine, California, USA
| | - Philip D Kiser
- Department of Ophthalmology, School of Medicine, University of California, Irvine, Irvine, California, USA; Department of Physiology & Biophysics, School of Medicine, University of California, Irvine, Irvine, California, USA; Research Service, VA Long Beach Healthcare System, Long Beach, California, USA.
| | - Brad S Pierce
- Department of Chemistry & Biochemistry, University of Alabama, Tuscaloosa, Alabama, USA.
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16
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Flückger S, Igareta NV, Seebeck FP. Convergent Evolution of Fungal Cysteine Dioxygenases. Chembiochem 2020; 21:3082-3086. [PMID: 32543095 DOI: 10.1002/cbic.202000317] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Revised: 06/11/2020] [Indexed: 12/16/2022]
Abstract
Cupin-type cysteine dioxygenases (CDOs) are non-heme iron enzymes that occur in animals, plants, bacteria and in filamentous fungi. In this report, we show that agaricomycetes contain an entirely unrelated type of CDO that emerged by convergent evolution from enzymes involved in the biosynthesis of ergothioneine. The activity of this CDO type is dependent on the ergothioneine precursor N-α-trimethylhistidine. The metabolic link between ergothioneine production and cysteine oxidation suggests that the two processes might be part of the same chemical response in fungi, for example against oxidative stress.
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Affiliation(s)
- Sebastian Flückger
- Department for Chemistry, University of Basel, Mattenstrasse 24a, 4002, Basel, Switzerland
| | - Nico V Igareta
- Department for Chemistry, University of Basel, Mattenstrasse 24a, 4002, Basel, Switzerland
| | - Florian P Seebeck
- Department for Chemistry, University of Basel, Mattenstrasse 24a, 4002, Basel, Switzerland
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17
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Fernandez RL, Dillon SL, Stipanuk MH, Fox BG, Brunold TC. Spectroscopic Investigation of Cysteamine Dioxygenase. Biochemistry 2020; 59:2450-2458. [PMID: 32510930 DOI: 10.1021/acs.biochem.0c00267] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Thiol dioxygenases are mononuclear non-heme FeII-dependent metalloenzymes that initiate the oxidative catabolism of thiol-containing substrates to their respective sulfinates. Cysteine dioxygenase (CDO), the best characterized mammalian thiol dioxygenase, contains a three-histidine (3-His) coordination environment rather than the 2-His-1-carboxylate facial triad seen in most mononuclear non-heme FeII enzymes. A similar 3-His active site is found in the bacterial thiol dioxygenase 3-mercaptopropionate dioxygenase (MDO), which converts 3-mercaptopropionate into 3-sulfinopropionic acid as part of the bacterial sulfur metabolism pathway. In this study, we have investigated the active site geometric and electronic structures of a third non-heme FeII-dependent thiol dioxygenase, cysteamine dioxygenase (ADO), by using a spectroscopic approach. Although a 3-His facial triad had previously been implicated on the basis of sequence alignment and site-directed mutagenesis studies, little is currently known about the active site environment of ADO. Our magnetic circular dichroism and electron paramagnetic resonance data provide compelling evidence that ADO features a 3-His facial triad, like CDO and MDO. Despite this similar coordination environment, spectroscopic results obtained for ADO incubated with various substrate analogues are distinct from those obtained for the other FeII-dependent thiol dioxygenases. This finding suggests that the secondary coordination sphere of ADO is distinct from those of CDO and MDO, demonstrating the significant role that secondary-sphere residues play in dictating substrate specificity.
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Affiliation(s)
- Rebeca L Fernandez
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Stephanie L Dillon
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Martha H Stipanuk
- Department of Nutritional Sciences, Cornell University, Ithaca, New York 14853, United States
| | - Brian G Fox
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Thomas C Brunold
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
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18
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Wang Y, Davis I, Chan Y, Naik SG, Griffith WP, Liu A. Characterization of the nonheme iron center of cysteamine dioxygenase and its interaction with substrates. J Biol Chem 2020; 295:11789-11802. [PMID: 32601061 DOI: 10.1074/jbc.ra120.013915] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Revised: 06/25/2020] [Indexed: 12/15/2022] Open
Abstract
Cysteamine dioxygenase (ADO) has been reported to exhibit two distinct biological functions with a nonheme iron center. It catalyzes oxidation of both cysteamine in sulfur metabolism and N-terminal cysteine-containing proteins or peptides, such as regulator of G protein signaling 5 (RGS5). It thereby preserves oxygen homeostasis in a variety of physiological processes. However, little is known about its catalytic center and how it interacts with these two types of primary substrates in addition to O2 Here, using electron paramagnetic resonance (EPR), Mössbauer, and UV-visible spectroscopies, we explored the binding mode of cysteamine and RGS5 to human and mouse ADO proteins in their physiologically relevant ferrous form. This characterization revealed that in the presence of nitric oxide as a spin probe and oxygen surrogate, both the small molecule and the peptide substrates coordinate the iron center with their free thiols in a monodentate binding mode, in sharp contrast to binding behaviors observed in other thiol dioxygenases. We observed a substrate-bound B-type dinitrosyl iron center complex in ADO, suggesting the possibility of dioxygen binding to the iron ion in a side-on mode. Moreover, we observed substrate-mediated reduction of the iron center from ferric to the ferrous oxidation state. Subsequent MS analysis indicated corresponding disulfide formation of the substrates, suggesting that the presence of the substrate could reactivate ADO to defend against oxidative stress. The findings of this work contribute to the understanding of the substrate interaction in ADO and fill a gap in our knowledge of the substrate specificity of thiol dioxygenases.
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Affiliation(s)
- Yifan Wang
- Department of Chemistry, University of Texas at San Antonio, Texas, USA
| | - Ian Davis
- Department of Chemistry, University of Texas at San Antonio, Texas, USA.,Department of Chemistry, Georgia State University, Atlanta, Georgia, USA
| | - Yan Chan
- Department of Chemistry, Georgia State University, Atlanta, Georgia, USA
| | - Sunil G Naik
- Department of Chemistry, University of Texas at San Antonio, Texas, USA
| | | | - Aimin Liu
- Department of Chemistry, University of Texas at San Antonio, Texas, USA .,Department of Chemistry, Georgia State University, Atlanta, Georgia, USA
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19
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Forbes DL, Meneely KM, Chilton AS, Lamb AL, Ellis HR. The 3-His Metal Coordination Site Promotes the Coupling of Oxygen Activation to Cysteine Oxidation in Cysteine Dioxygenase. Biochemistry 2020; 59:2022-2031. [PMID: 32368901 DOI: 10.1021/acs.biochem.9b01085] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Cysteine dioxygenase (CDO) structurally resembles cupin enzymes that use a 3-His/1-Glu coordination scheme. However, the glutamate ligand is substituted with a cysteine (Cys93) residue, which forms a thioether bond with tyrosine (Tyr157) under physiological conditions. The reversion variant, C93E CDO, was generated in order to reestablish the more common 3-His/1-Glu metal ligands of the cupin superfamily. This variant provides a framework for testing the structural and functional significance of Cys93 and the cross-link in CDO. Although dioxygen consumption was observed with C93E CDO, it was not coupled with l-cysteine oxidation. Substrate analogues (d-cysteine, cysteamine, and 3-mercaptopropionate) were not viable substrates for the C93E CDO variant, although they showed variable coordinations to the iron center. The structures of C93E and cross-linked and non-cross-linked wild-type CDO were solved by X-ray crystallography to 1.91, 2.49, and 2.30 Å, respectively. The C93E CDO variant had similar overall structural properties compared to cross-linked CDO; however, the iron was coordinated by a 3-His/1-Glu geometry, leaving only two coordination sites available for dioxygen and bidentate l-cysteine binding. The hydroxyl group of Tyr157 shifted in both non-cross-linked and C93E CDO, and this displacement prevented the residue from participating in substrate stabilization. Based on these results, the divergence of the metal center of cysteine dioxygenase from the 3-His/1-Glu geometry seen with many cupin enzymes was essential for effective substrate binding. The substitution of Glu with Cys in CDO allows for a third coordination site on the iron for bidentate cysteine and monodentate oxygen binding.
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Affiliation(s)
- Dianna L Forbes
- The Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849, United States
| | - Kathleen M Meneely
- Molecular Biosciences, University of Kansas, 1200 Sunnyside Avenue, Lawrence, Kansas 66045, United States
| | - Annemarie S Chilton
- Molecular Biosciences, University of Kansas, 1200 Sunnyside Avenue, Lawrence, Kansas 66045, United States
| | - Audrey L Lamb
- Molecular Biosciences, University of Kansas, 1200 Sunnyside Avenue, Lawrence, Kansas 66045, United States
| | - Holly R Ellis
- The Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849, United States
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20
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Sardar S, Weitz A, Hendrich MP, Pierce BS. Outer-Sphere Tyrosine 159 within the 3-Mercaptopropionic Acid Dioxygenase S-H-Y Motif Gates Substrate-Coordination Denticity at the Non-Heme Iron Active Site. Biochemistry 2019; 58:5135-5150. [PMID: 31750652 PMCID: PMC10071547 DOI: 10.1021/acs.biochem.9b00674] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Thiol dioxygenases are non-heme mononuclear iron enzymes that catalyze the O2-dependent oxidation of free thiols (-SH) to produce the corresponding sulfinic acid (-SO2-). Regardless of the phylogenic domain, the active site for this enzyme class is typically comprised of two major features: (1) a mononuclear ferrous iron coordinated by three protein-derived histidines and (2) a conserved sequence of outer Fe-coordination-sphere amino acids (Ser-His-Tyr) spatially adjacent to the iron site (∼3 Å). Here, we utilize a promiscuous 3-mercaptopropionic acid dioxygenase cloned from Azotobacter vinelandii (Av MDO) to explore the function of the conserved S-H-Y motif. This enzyme exhibits activity with 3-mercaptopropionic acid (3mpa), l-cysteine (cys), as well as several other thiol-bearing substrates, thus making it an ideal system to study the influence of residues within the highly conserved S-H-Y motif (H157 and Y159) on substrate specificity and reactivity. The pKa values for these residues were determined by pH-dependent steady-state kinetics, and their assignments verified by comparison to H157N and Y159F variants. Complementary electron paramagnetic resonance and Mössbauer studies demonstrate a network of hydrogen bonds connecting H157-Y159 and Fe-bound ligands within the enzymatic Fe site. Crucially, these experiments suggest that the hydroxyl group of Y159 hydrogen bonds to Fe-bound NO and, by extension, Fe-bound oxygen during native catalysis. This interaction alters both the NO binding affinity and rhombicity of the 3mpa-bound iron-nitrosyl site. In addition, Fe coordination of cys is switched from thiolate only to bidentate (thiolate/amine) for the Y159F variant, indicating that perturbations within the S-H-Y proton relay network also influence cys Fe binding denticity.
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Affiliation(s)
- Sinjinee Sardar
- Department of Chemistry and Biochemistry , The University of Texas at Arlington , 700 Planetarium Place , Arlington , Texas 76019 , United States
| | - Andrew Weitz
- Department of Chemistry , Carnegie Mellon University , 4400 Fifth Avenue , Pittsburgh , Pennsylvania 15213 , United States
| | - Michael P Hendrich
- Department of Chemistry , Carnegie Mellon University , 4400 Fifth Avenue , Pittsburgh , Pennsylvania 15213 , United States
| | - Brad S Pierce
- Department of Chemistry and Biochemistry , University of Alabama , 250 Hackberry Lane , Tuscaloosa , Alabama 35487 , United States
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21
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Fischer AA, Miller JR, Jodts RJ, Ekanayake DM, Lindeman SV, Brunold TC, Fiedler AT. Spectroscopic and Computational Comparisons of Thiolate-Ligated Ferric Nonheme Complexes to Cysteine Dioxygenase: Second-Sphere Effects on Substrate (Analogue) Positioning. Inorg Chem 2019; 58:16487-16499. [PMID: 31789510 DOI: 10.1021/acs.inorgchem.9b02432] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Parallel spectroscopic and computational studies of iron(III) cysteine dioxygenase (CDO) and synthetic models are presented. The synthetic complexes utilize the ligand tris(4,5-diphenyl-1-methylimidazol-2-yl)phosphine (Ph2TIP), which mimics the facial three-histidine triad of CDO and other thiol dioxygenases. In addition to the previously reported [FeII(CysOEt)(Ph2TIP)]BPh4 (1; CysOEt is the ethyl ester of anionic l-cysteine), the formation and crystallographic characterization of [FeII(2-MTS)(Ph2TIP)]BPh4 (2) is reported, where the methyl 2-thiosalicylate anion (2-MTS) resembles the substrate of 3-mercaptopropionate dioxygenase (MDO). One-electron chemical oxidation of 1 and 2 yields ferric species that bind cyanide and azide anions, which have been used as spectroscopic probes of O2 binding in prior studies of FeIII-CDO. The six-coordinate FeIII-CN and FeIII-N3 adducts are examined with UV-vis absorption, electron paramagnetic resonance (EPR), and resonance Raman (rRaman) spectroscopies. In addition, UV-vis and rRaman studies of cysteine- and cyanide-bound FeIII-CDO are reported for both the wild-type (WT) enzyme and C93G variant, which lacks the Cys-Tyr cross-link that is present in the second coordination sphere of the WT active site. Density functional theory (DFT) and ab initio calculations are employed to provide geometric and electronic structure descriptions of the synthetic and enzymatic FeIII adducts. In particular, it is shown that the complete active space self-consistent field (CASSCF) method, in tandem with n-electron valence state second-order perturbation theory (NEVPT2), is capable of elucidating the structural basis of subtle shifts in EPR g values for low-spin FeIII species.
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Affiliation(s)
- Anne A Fischer
- Department of Chemistry , Marquette University , Milwaukee , Wisconsin 53201 , United States
| | - Joshua R Miller
- Department of Chemistry , University of Wisconsin-Madison , Madison , Wisconsin 53706 , United States
| | - Richard J Jodts
- Department of Chemistry , University of Wisconsin-Madison , Madison , Wisconsin 53706 , United States
| | - Danushka M Ekanayake
- Department of Chemistry , Marquette University , Milwaukee , Wisconsin 53201 , United States
| | - Sergey V Lindeman
- Department of Chemistry , Marquette University , Milwaukee , Wisconsin 53201 , United States
| | - Thomas C Brunold
- Department of Chemistry , University of Wisconsin-Madison , Madison , Wisconsin 53706 , United States
| | - Adam T Fiedler
- Department of Chemistry , Marquette University , Milwaukee , Wisconsin 53201 , United States
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22
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Anandababu K, Ramasubramanian R, Wadepohl H, Comba P, Johnee Britto N, Jaccob M, Mayilmurugan R. A Structural and Functional Model for the Tris-Histidine Motif in Cysteine Dioxygenase. Chemistry 2019; 25:9540-9547. [PMID: 31090109 DOI: 10.1002/chem.201901005] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Revised: 04/23/2019] [Indexed: 01/14/2023]
Abstract
The iron(II) complexes [Fe(L)(MeCN)3 ](SO3 CF3 )2 (L are two derivatives of tris(2-pyridyl)-based ligands) have been synthesized as models for cysteine dioxygenase (CDO). The molecular structure of one of the complexes exhibits octahedral coordination geometry and the Fe-Npy bond lengths [1.953(4)-1.972(4) Å] are similar to those in the Cys-bound FeII -CDO; Fe-NHis : 1.893-2.199 Å. The iron(II) centers of the model complexes exhibit relatively high FeIII/II redox potentials (E1/2 =0.988-1.380 V vs. ferrocene/ferrocenium electrode, Fc/Fc+ ), within the range for O2 activation and typical for the corresponding nonheme iron enzymes. The reaction of in situ generated [Fe(L)(MeCN)(SPh)]+ with excess O2 in acetonitrile (MeCN) yields selectively the doubly oxygenated phenylsulfinic acid product. Isotopic labeling studies using 18 O2 confirm the incorporation of both oxygen atoms of O2 into the product. Kinetic and preliminary DFT studies reveal the involvement of an FeIII peroxido intermediate with a rhombic S= 1 / 2 FeIII center (687-696 nm; g≈2.46-2.48, 2.13-2.15, 1.92-1.94), similar to the spectroscopic signature of the low-spin Cys-bound FeIII CDO (650 nm, g≈2.47, 2.29, 1.90). The proposed FeIII peroxido intermediates have been trapped, and the O-O stretching frequencies are in the expected range (approximately 920 and 820 cm-1 for the alkyl- and hydroperoxido species, respectively). The model complexes have a structure similar to that of the enzyme and structural aspects as well as the reactivity are discussed.
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Affiliation(s)
- Karunanithi Anandababu
- Bioinorganic Chemistry Laboratory/Physical Chemistry, School of Chemistry, Madurai Kamaraj University, Madurai, 625021, India
| | - Ramamoorthy Ramasubramanian
- Bioinorganic Chemistry Laboratory/Physical Chemistry, School of Chemistry, Madurai Kamaraj University, Madurai, 625021, India
| | - Hubert Wadepohl
- Anorganisch-Chemisches Institut and Interdisciplinary Center for Scientific Computing, Universität Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany
| | - Peter Comba
- Anorganisch-Chemisches Institut and Interdisciplinary Center for Scientific Computing, Universität Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany
| | | | - Madhavan Jaccob
- Department of Chemistry, Loyola College, Chennai, 600034, India
| | - Ramasamy Mayilmurugan
- Bioinorganic Chemistry Laboratory/Physical Chemistry, School of Chemistry, Madurai Kamaraj University, Madurai, 625021, India
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23
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Aloi S, Davies CG, Karplus PA, Wilbanks SM, Jameson GNL. Substrate Specificity in Thiol Dioxygenases. Biochemistry 2019; 58:2398-2407. [PMID: 31045343 DOI: 10.1021/acs.biochem.9b00079] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Thiol dioxygenases make up a class of ferrous iron-dependent enzymes that oxidize thiols to their corresponding sulfinates. X-ray diffraction structures of cysteine-bound cysteine dioxygenase show how cysteine is coordinated via its thiolate and amine to the iron and oriented correctly for O atom transfer. There are currently no structures with 3-mercaptopropionic acid or mercaptosuccinic acid bound to their respective enzymes, 3-mercaptopropionate dioxygenase or mercaptosuccinate dioxygenase. Sequence alignments and comparisons of known structures have led us to postulate key structural features that define substrate specificity. Here, we compare the rates and reactivities of variants of Rattus norvegicus cysteine dioxygenase and 3-mercaptopropionate dioxygenases from Pseudomonas aureginosa and Ralstonia eutropha (JMP134) and show how binary variants of three structural features correlate with substrate specificity and reactivity. They are (1) the presence or absence of a cis-peptide bond between residues Ser158 and Pro159, (2) an Arg or Gln at position 60, and (3) a Cys or Arg at position 164 (all RnCDO numbering). Different permutations of these features allow sulfination of l-cysteine, 3-mercaptopropionic acid, and ( R)-mercaptosuccinic acid to be promoted or impeded.
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Affiliation(s)
- Sekotilani Aloi
- Department of Chemistry , University of Otago , P.O. Box 56, Dunedin 9054 , New Zealand
| | - Casey G Davies
- Department of Chemistry , University of Otago , P.O. Box 56, Dunedin 9054 , New Zealand
| | - P Andrew Karplus
- Department of Biochemistry and Biophysics , Oregon State University , 2011 Ag & Life Sciences Building , Corvallis , Oregon 97331 , United States
| | - Sigurd M Wilbanks
- Department of Biochemistry , University of Otago , P.O. Box 56, Dunedin 9054 , New Zealand
| | - Guy N L Jameson
- Department of Chemistry , University of Otago , P.O. Box 56, Dunedin 9054 , New Zealand.,School of Chemistry, Bio21 Molecular Science and Biotechnology Institute , The University of Melbourne , 30 Flemington Road , Parkville , VIC 3010 , Australia
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24
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Li J, Koto T, Davis I, Liu A. Probing the Cys-Tyr Cofactor Biogenesis in Cysteine Dioxygenase by the Genetic Incorporation of Fluorotyrosine. Biochemistry 2019; 58:2218-2227. [PMID: 30946568 DOI: 10.1021/acs.biochem.9b00006] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Cysteine dioxygenase (CDO) is a nonheme iron enzyme that adds two oxygen atoms from dioxygen to the sulfur atom of l-cysteine. Adjacent to the iron site of mammalian CDO, there is a post-translationally generated Cys-Tyr cofactor, whose presence substantially enhances the oxygenase activity. The formation of the Cys-Tyr cofactor in CDO is an autocatalytic process, and it is challenging to study by traditional techniques because the cross-linking reaction is a side, uncoupled, single-turnover oxidation buried among multiple turnovers of l-cysteine oxygenation. Here, we take advantage of our recent success in obtaining a purely uncross-linked human CDO due to site-specific incorporation of 3,5-difluoro-l-tyrosine (F2-Tyr) at the cross-linking site through the genetic code expansion strategy. Using EPR spectroscopy, we show that nitric oxide (•NO), an oxygen surrogate, similarly binds to uncross-linked F2-Tyr157 CDO as in wild-type human CDO. We determined X-ray crystal structures of uncross-linked F2-Tyr157 CDO and mature wild-type CDO in complex with both l-cysteine and •NO. These structural data reveal that the active site cysteine (Cys93 in the human enzyme), rather than the generally expected tyrosine (i.e., Tyr157), is well-aligned to be oxidized should the normal oxidation reaction uncouple. This structure-based understanding is further supported by a computational study with models built on the uncross-linked ternary complex structure. Together, these results strongly suggest that the first target to oxidize during the iron-assisted Cys-Tyr cofactor biogenesis is Cys93. Based on these data, a plausible reaction mechanism implementing a cysteine radical involved in the cross-link formation is proposed.
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Affiliation(s)
- Jiasong Li
- Department of Chemistry , University of Texas at San Antonio , San Antonio , Texas 78249 , United States
| | - Teruaki Koto
- Department of Chemistry , University of Texas at San Antonio , San Antonio , Texas 78249 , United States
| | - Ian Davis
- Department of Chemistry , University of Texas at San Antonio , San Antonio , Texas 78249 , United States
| | - Aimin Liu
- Department of Chemistry , University of Texas at San Antonio , San Antonio , Texas 78249 , United States
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25
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Blakely MN, Dedushko MA, Yan Poon PC, Villar-Acevedo G, Kovacs JA. Formation of a Reactive, Alkyl Thiolate-Ligated Fe III-Superoxo Intermediate Derived from Dioxygen. J Am Chem Soc 2019; 141:1867-1870. [PMID: 30661357 DOI: 10.1021/jacs.8b12670] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Herein, we describe an alkyl thiolate-ligated iron complex that reacts with dioxygen to form an unprecedented example of an iron superoxo (O2•-) intermediate, [FeIII(S2Me2N3(Pr,Pr))(O2)] (4), which is capable of cleaving strong C-H bonds. A cysteinate-ligated iron superoxo intermediate is proposed to play a key role in the biosynthesis of β-lactam antibiotics by isopenicillin N-synthase (IPNS). Superoxo 4 converts to a metastable putative Fe(III)-OOH intermediate, at rates that are dependent on the C-H bond strength of the H atom donor, with a kinetic isotope effect ( kH/ kD = 4.8) comparable to that of IPNS ( kH/ kD = 5.6). The bond dissociation energy of the C-H bonds cleaved by 4 (92 kcal/mol) is comparable to C-H bonds cleaved by IPNS (93 kcal/mol). Both the calculated and experimental electronic absorption spectra of 4 are comparable to those of the putative IPNS superoxo intermediate, and are shown to involve RS- → Fe-O2•- and O2•- → Fe charge transfer transitions. The π-back-donation by the electron-rich alkyl thiolate presumably facilitates this reactivity by increasing the basicity of the distal oxygen. The frontier orbitals of 4 are shown to consist of two strongly coupled unpaired electrons of opposite spin, one in a superoxo π*(O-O) orbital, and the other in an Fe(d xy) orbital.
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Affiliation(s)
- Maike N Blakely
- Department of Chemistry , University of Washington , Campus Box 351700 , Seattle , Washington 98195 , United States
| | - Maksym A Dedushko
- Department of Chemistry , University of Washington , Campus Box 351700 , Seattle , Washington 98195 , United States
| | - Penny Chaau Yan Poon
- Department of Chemistry , University of Washington , Campus Box 351700 , Seattle , Washington 98195 , United States
| | - Gloria Villar-Acevedo
- Department of Chemistry , University of Washington , Campus Box 351700 , Seattle , Washington 98195 , United States
| | - Julie A Kovacs
- Department of Chemistry , University of Washington , Campus Box 351700 , Seattle , Washington 98195 , United States
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26
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Gordon JB, McGale JP, Prendergast JR, Shirani-Sarmazeh Z, Siegler MA, Jameson GNL, Goldberg DP. Structures, Spectroscopic Properties, and Dioxygen Reactivity of 5- and 6-Coordinate Nonheme Iron(II) Complexes: A Combined Enzyme/Model Study of Thiol Dioxygenases. J Am Chem Soc 2018; 140:14807-14822. [PMID: 30346746 PMCID: PMC6596423 DOI: 10.1021/jacs.8b08349] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The synthesis of four new FeII(N4S(thiolate)) complexes as models of the thiol dioxygenases are described. They are composed of derivatives of the neutral, tridentate ligand triazacyclononane (R3TACN; R = Me, iPr) and 2-aminobenzenethiolate (abtx; X = H, CF3), a non-native substrate for thiol dioxygenases. The coordination number of these complexes depends on the identity of the TACN derivative, giving 6-coordinate (6-coord) complexes for FeII(Me3TACN)(abtx)(OTf) (1: X = H; 2: X = CF3) and 5-coordinate (5-coord) complexes for [FeII(iPr3TACN)(abtx)](OTf) (3: X = H; 4: X = CF3). Complexes 1-4 were examined by UV-vis, 1H/19F NMR, and Mössbauer spectroscopies, and density functional theory (DFT) calculations were employed to support the data. Mössbauer spectroscopy reveals that the 6-coord 1-2 and 5-coord 3- 4 exhibit distinct spectra, and these data are compared with that for cysteine-bound CDO, helping to clarify the coordination environment of the cys-bound FeII active site. Reaction of 1 or 2 with O2 at -95 °C leads to S-oxygenation of the abt ligand, and in the case of 2, a rare di(sulfinato)-bridged complex, [Fe2III(μ-O)((2-NH2) p-CF3C6H3SO2)2](OTf)2 ( 5), was obtained. Parallel enzymatic studies on the CDO variant C93G were carried out with the abt substrate and show that reaction with O2 leads to disulfide formation, as opposed to S-oxygenation. The combined model and enzyme studies show that the thiol dioxygenases can operate via a 6-coord FeII center, in contrast to the accepted mechanism for nonheme iron dioxygenases, and that proper substrate chelation to Fe appears to be critical for S-oxygenation.
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Affiliation(s)
- Jesse B Gordon
- Department of Chemistry , The Johns Hopkins University , 3400 North Charles Street , Baltimore , Maryland 21218 , United States
- School of Chemistry , Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne , 30 Flemington Road , Parkville , Victoria 3010 , Australia
| | - Jeremy P McGale
- Department of Chemistry , The Johns Hopkins University , 3400 North Charles Street , Baltimore , Maryland 21218 , United States
- School of Chemistry , Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne , 30 Flemington Road , Parkville , Victoria 3010 , Australia
| | - Joshua R Prendergast
- Department of Chemistry , The Johns Hopkins University , 3400 North Charles Street , Baltimore , Maryland 21218 , United States
- School of Chemistry , Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne , 30 Flemington Road , Parkville , Victoria 3010 , Australia
| | - Zahra Shirani-Sarmazeh
- Department of Chemistry , The Johns Hopkins University , 3400 North Charles Street , Baltimore , Maryland 21218 , United States
- School of Chemistry , Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne , 30 Flemington Road , Parkville , Victoria 3010 , Australia
| | - Maxime A Siegler
- Department of Chemistry , The Johns Hopkins University , 3400 North Charles Street , Baltimore , Maryland 21218 , United States
- School of Chemistry , Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne , 30 Flemington Road , Parkville , Victoria 3010 , Australia
| | - Guy N L Jameson
- Department of Chemistry , The Johns Hopkins University , 3400 North Charles Street , Baltimore , Maryland 21218 , United States
- School of Chemistry , Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne , 30 Flemington Road , Parkville , Victoria 3010 , Australia
| | - David P Goldberg
- Department of Chemistry , The Johns Hopkins University , 3400 North Charles Street , Baltimore , Maryland 21218 , United States
- School of Chemistry , Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne , 30 Flemington Road , Parkville , Victoria 3010 , Australia
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27
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Goudarzi S, Babicz JT, Kabil O, Banerjee R, Solomon EI. Spectroscopic and Electronic Structure Study of ETHE1: Elucidating the Factors Influencing Sulfur Oxidation and Oxygenation in Mononuclear Nonheme Iron Enzymes. J Am Chem Soc 2018; 140:14887-14902. [PMID: 30362717 DOI: 10.1021/jacs.8b09022] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
ETHE1 is a member of a growing subclass of nonheme Fe enzymes that catalyzes transformations of sulfur-containing substrates without a cofactor. ETHE1 dioxygenates glutathione persulfide (GSSH) to glutathione (GSH) and sulfite in a reaction which is similar to that of cysteine dioxygenase (CDO), but with monodentate (vs bidentate) substrate coordination and a 2-His/1-Asp (vs 3-His) ligand set. In this study, we demonstrate that GSS- binds directly to the iron active site, causing coordination unsaturation to prime the site for O2 activation. Nitrosyl complexes without and with GSSH were generated and spectroscopically characterized as unreactive analogues for the invoked ferric superoxide intermediate. New spectral features from persulfide binding to the FeIII include the appearance of a low-energy FeIII ligand field transition, an energy shift of a NO- to FeIII CT transition, and two new GSS- to FeIII CT transitions. Time-dependent density functional theory calculations were used to simulate the experimental spectra to determine the persulfide orientation. Correlation of these spectral features with those of monodentate cysteine binding in isopenicillin N synthase (IPNS) shows that the persulfide is a poorer donor but still results in an equivalent frontier molecular orbital for reactivity. The ETHE1 persulfide dioxygenation reaction coordinate was calculated, and while the initial steps are similar to the reaction coordinate of CDO, an additional hydrolysis step is required in ETHE1 to break the S-S bond. Unlike ETHE1 and CDO, which both oxygenate sulfur, IPNS oxidizes sulfur through an initial H atom abstraction. Thus, factors that determine oxygenase vs oxidase reactivity were evaluated. In general, sulfur oxygenation is thermodynamically favored and has a lower barrier for reactivity. However, in IPNS, second-sphere residues in the active site pocket constrain the substrate, raising the barrier for sulfur oxygenation relative to oxidation via H atom abstraction.
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Affiliation(s)
- Serra Goudarzi
- Department of Chemistry , Stanford University , Stanford , California 94305 , United States
| | - Jeffrey T Babicz
- Department of Chemistry , Stanford University , Stanford , California 94305 , United States
| | - Omer Kabil
- Department of Biological Chemistry , University of Michigan Medical School , Ann Arbor , Michigan 48109 , United States
| | - Ruma Banerjee
- Department of Biological Chemistry , University of Michigan Medical School , Ann Arbor , Michigan 48109 , United States
| | - Edward I Solomon
- Department of Chemistry , Stanford University , Stanford , California 94305 , United States.,SLAC National Accelerator Laboratory , Menlo Park , California 94025 , United States
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28
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Fischer AA, Lindeman SV, Fiedler AT. A synthetic model of the nonheme iron-superoxo intermediate of cysteine dioxygenase. Chem Commun (Camb) 2018; 54:11344-11347. [PMID: 30246208 PMCID: PMC6201693 DOI: 10.1039/c8cc06247a] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A nonheme Fe(ii) complex (1) that models substrate-bound cysteine dioxygenase (CDO) reacts with O2 at -80 °C to yield a purple intermediate (2). Analysis with spectroscopic and computational methods determined that 2 features a thiolate-ligated Fe(iii) center bound to a superoxide radical, mimicking the putative structure of a key CDO intermediate.
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Affiliation(s)
- Anne A Fischer
- Department of Chemistry, Marquette University, 1414 W. Clybourn St., Milwaukee, WI 53233, USA.
| | - Sergey V Lindeman
- Department of Chemistry, Marquette University, 1414 W. Clybourn St., Milwaukee, WI 53233, USA.
| | - Adam T Fiedler
- Department of Chemistry, Marquette University, 1414 W. Clybourn St., Milwaukee, WI 53233, USA.
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29
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Morrow WP, Sardar S, Thapa P, Hossain MS, Foss FW, Pierce BS. Thiol dioxygenase turnover yields benzothiazole products from 2-mercaptoaniline and O 2-dependent oxidation of primary alcohols. Arch Biochem Biophys 2017; 631:66-74. [PMID: 28826737 PMCID: PMC5616182 DOI: 10.1016/j.abb.2017.08.013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Revised: 08/15/2017] [Accepted: 08/16/2017] [Indexed: 10/19/2022]
Abstract
Thiol dioxygenases are non-heme mononuclear iron enzymes that catalyze the O2-dependent oxidation of free thiols (-SH) to produce the corresponding sulfinic acid (-SO2-). Previous chemical rescue studies identified a putative FeIII-O2- intermediate that precedes substrate oxidation in Mus musculus cysteine dioxygenase (Mm CDO). Given that a similar reactive intermediate has been identified in the extradiol dioxygenase 2, 3-HCPD, it is conceivable that these enzymes share other mechanistic features with regard to substrate oxidation. To explore this possibility, enzymatic reactions with Mm CDO (as well as the bacterial 3-mercaptopropionic acid dioxygenase, Av MDO) were performed using a substrate analogue (2-mercaptoaniline, 2ma). This aromatic thiol closely approximates the catecholic substrate of homoprotocatechuate of 2, 3-HPCD while maintaining the 2-carbon thiol-amine separation preferred by Mm CDO. Remarkably, both enzymes exhibit 2ma-gated O2-consumption; however, none of the expected products for thiol dioxygenase or intra/extradiol dioxygenase reactions were observed. Instead, benzothiazoles are produced by the condensation of 2ma with aldehydes formed by an off-pathway oxidation of primary alcohols added to aqueous reactions to solubilize the substrate. The observed oxidation of 1º-alcohols in 2ma-reactions is consistent with the formation of a high-valent intermediate similar to what has been reported for cytochrome P450 and mononuclear iron model complexes.
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Affiliation(s)
- William P Morrow
- Department of Chemistry & Biochemistry, College of Science, The University of Texas at Arlington, Arlington, TX 76019, United States
| | - Sinjinee Sardar
- Department of Chemistry & Biochemistry, College of Science, The University of Texas at Arlington, Arlington, TX 76019, United States
| | - Pawan Thapa
- Department of Chemistry & Biochemistry, College of Science, The University of Texas at Arlington, Arlington, TX 76019, United States
| | - Mohammad S Hossain
- Department of Chemistry & Biochemistry, College of Science, The University of Texas at Arlington, Arlington, TX 76019, United States
| | - Frank W Foss
- Department of Chemistry & Biochemistry, College of Science, The University of Texas at Arlington, Arlington, TX 76019, United States
| | - Brad S Pierce
- Department of Chemistry & Biochemistry, College of Science, The University of Texas at Arlington, Arlington, TX 76019, United States.
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30
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Fischer AA, Lindeman SV, Fiedler AT. Spectroscopic and computational studies of reversible O2 binding by a cobalt complex of relevance to cysteine dioxygenase. Dalton Trans 2017; 46:13229-13241. [DOI: 10.1039/c7dt01600j] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Spectroscopic and computational studies of reversible O2 binding by a cobalt active-site mimic shed light on the catalytic mechanism of cysteine dioxygenases.
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31
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Fischer AA, Stracey N, Lindeman SV, Brunold TC, Fiedler AT. Synthesis, X-ray Structures, Electronic Properties, and O 2/NO Reactivities of Thiol Dioxygenase Active-Site Models. Inorg Chem 2016; 55:11839-11853. [PMID: 27801576 DOI: 10.1021/acs.inorgchem.6b01931] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Mononuclear non-heme iron complexes that serve as structural and functional mimics of the thiol dioxygenases (TDOs), cysteine dioxygenase (CDO) and cysteamine dioxygenase (ADO), have been prepared and characterized with crystallographic, spectroscopic, kinetic, and computational methods. The high-spin Fe(II) complexes feature the facially coordinating tris(4,5-diphenyl-1-methylimidazol-2-yl)phosphine (Ph2TIP) ligand that replicates the three histidine (3His) triad of the TDO active sites. Further coordination with bidentate l-cysteine ethyl ester (CysOEt) or cysteamine (CysAm) anions yielded five-coordinate (5C) complexes that resemble the substrate-bound forms of CDO and ADO, respectively. Detailed electronic-structure descriptions of the [Fe(Ph2TIP)(LS,N)]BPh4 complexes, where LS,N = CysOEt (1) or CysAm (2), were generated through a combination of spectroscopic techniques [electronic absorption, magnetic circular dichroism (MCD)] and density functional theory (DFT). Complexes 1 and 2 decompose in the presence of O2 to yield the corresponding sulfinic acid (RSO2H) products, thereby emulating the reactivity of the TDO enzymes and related complexes. Rate constants and activation parameters for the dioxygenation reactions were measured and interpreted with the aid of DFT calculations for O2-bound intermediates. Treatment of the TDO models with nitric oxide (NO)-a well-established surrogate of O2-led to a mixture of high-spin and low-spin {FeNO}7 species at low temperature (-70 °C), as indicated by electron paramagnetic resonance (EPR) spectroscopy. At room temperature, these Fe/NO adducts convert to a common species with EPR and infrared (IR) features typical of cationic dinitrosyl iron complexes (DNICs). To complement these results, parallel spectroscopic, computational, and O2/NO reactivity studies were carried out using previously reported TDO models that feature an anionic hydrotris(3-phenyl-5-methyl-pyrazolyl)borate (Ph,MeTp-) ligand. Though the O2 reactivities of the Ph2TIP- and Ph,MeTp-based complexes are quite similar, the supporting ligand perturbs the energies of Fe 3d-based molecular orbitals and modulates Fe-S bond covalency, suggesting possible rationales for the presence of neutral 3His coordination in CDO and ADO.
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Affiliation(s)
- Anne A Fischer
- Department of Chemistry, Marquette University , Milwaukee, Wisconsin 53201, United States
| | - Nuru Stracey
- Department of Chemistry, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
| | - Sergey V Lindeman
- Department of Chemistry, Marquette University , Milwaukee, Wisconsin 53201, United States
| | - Thomas C Brunold
- Department of Chemistry, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
| | - Adam T Fiedler
- Department of Chemistry, Marquette University , Milwaukee, Wisconsin 53201, United States
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32
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Peck SC, van der Donk WA. Go it alone: four-electron oxidations by mononuclear non-heme iron enzymes. J Biol Inorg Chem 2016; 22:381-394. [PMID: 27783267 DOI: 10.1007/s00775-016-1399-y] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2016] [Accepted: 10/11/2016] [Indexed: 10/20/2022]
Abstract
This review discusses the current mechanistic understanding of a group of mononuclear non-heme iron-dependent enzymes that catalyze four-electron oxidation of their organic substrates without the use of any cofactors or cosubstrates. One set of enzymes acts on α-ketoacid-containing substrates, coupling decarboxylation to oxygen activation. This group includes 4-hydroxyphenylpyruvate dioxygenase, 4-hydroxymandelate synthase, and CloR involved in clorobiocin biosynthesis. A second set of enzymes acts on substrates containing a thiol group that coordinates to the iron. This group is comprised of isopenicillin N synthase, thiol dioxygenases, and enzymes involved in the biosynthesis of ergothioneine and ovothiol. The final group of enzymes includes HEPD and MPnS that both carry out the oxidative cleavage of the carbon-carbon bond of 2-hydroxyethylphosphonate but generate different products. Commonalities amongst many of these enzymes are discussed and include the initial substrate oxidation by a ferric-superoxo-intermediate and a second oxidation by a ferryl species.
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Affiliation(s)
- Spencer C Peck
- Department of Chemistry and Howard Hughes Medical Institute, University of Illinois at Urbana-Champaign, 600 S. Mathews Ave., Urbana, IL, 61801, USA.,Institute for Genomic Biology, University of Illinois at Urbana-Champaign, 1206 West Gregory Drive, Urbana, IL, 61801, USA
| | - Wilfred A van der Donk
- Department of Chemistry and Howard Hughes Medical Institute, University of Illinois at Urbana-Champaign, 600 S. Mathews Ave., Urbana, IL, 61801, USA. .,Institute for Genomic Biology, University of Illinois at Urbana-Champaign, 1206 West Gregory Drive, Urbana, IL, 61801, USA.
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33
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Sahu S, Goldberg DP. Activation of Dioxygen by Iron and Manganese Complexes: A Heme and Nonheme Perspective. J Am Chem Soc 2016; 138:11410-28. [PMID: 27576170 DOI: 10.1021/jacs.6b05251] [Citation(s) in RCA: 229] [Impact Index Per Article: 28.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The rational design of well-defined, first-row transition metal complexes that can activate dioxygen has been a challenging goal for the synthetic inorganic chemist. The activation of O2 is important in part because of its central role in the functioning of metalloenzymes, which utilize O2 to perform a number of challenging reactions including the highly selective oxidation of various substrates. There is also great interest in utilizing O2, an abundant and environmentally benign oxidant, in synthetic catalytic oxidation systems. This Perspective brings together recent examples of biomimetic Fe and Mn complexes that can activate O2 in heme or nonheme-type ligand environments. The use of oxidants such as hypervalent iodine (e.g., ArIO), peracids (e.g., m-CPBA), peroxides (e.g., H2O2) or even superoxide is a popular choice for accessing well-characterized metal-superoxo, metal-peroxo, or metal-oxo species, but the instances of biomimetic Fe/Mn complexes that react with dioxygen to yield such observable metal-oxygen species are surprisingly few. This Perspective focuses on mononuclear Fe and Mn complexes that exhibit reactivity with O2 and lead to spectroscopically observable metal-oxygen species, and/or oxidize biologically relevant substrates. Analysis of these examples reveals that solvent, spin state, redox potential, external co-reductants, and ligand architecture can all play important roles in the O2 activation process.
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Affiliation(s)
- Sumit Sahu
- Department of Chemistry, The Johns Hopkins University , Baltimore, Maryland 21218, United States
| | - David P Goldberg
- Department of Chemistry, The Johns Hopkins University , Baltimore, Maryland 21218, United States
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Driggers CM, Kean KM, Hirschberger LL, Cooley RB, Stipanuk MH, Karplus PA. Structure-Based Insights into the Role of the Cys-Tyr Crosslink and Inhibitor Recognition by Mammalian Cysteine Dioxygenase. J Mol Biol 2016; 428:3999-4012. [PMID: 27477048 DOI: 10.1016/j.jmb.2016.07.012] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2016] [Revised: 07/15/2016] [Accepted: 07/18/2016] [Indexed: 10/21/2022]
Abstract
In mammals, the non-heme iron enzyme cysteine dioxygenase (CDO) helps regulate Cys levels through converting Cys to Cys sulfinic acid. Its activity is in part modulated by the formation of a Cys93-Tyr157 crosslink that increases its catalytic efficiency over 10-fold. Here, 21 high-resolution mammalian CDO structures are used to gain insight into how the Cys-Tyr crosslink promotes activity and how select competitive inhibitors bind. Crystal structures of crosslink-deficient C93A and Y157F variants reveal similar ~1.0-Å shifts in the side chain of residue 157, and both variant structures have a new chloride ion coordinating the active site iron. Cys binding is also different from wild-type CDO, and no Cys-persulfenate forms in the C93A or Y157F active sites at pH6.2 or 8.0. We conclude that the crosslink enhances activity by positioning the Tyr157 hydroxyl to enable proper Cys binding, proper oxygen binding, and optimal chemistry. In addition, structures are presented for homocysteine (Hcy), D-Cys, thiosulfate, and azide bound as competitive inhibitors. The observed binding modes of Hcy and D-Cys clarify why they are not substrates, and the binding of azide shows that in contrast to what has been proposed, it does not bind in these crystals as a superoxide mimic.
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Affiliation(s)
- Camden M Driggers
- Department of Biochemistry and Biophysics, 2011 Ag & Life Sciences Building, Oregon State University, Corvallis, OR 97331, USA
| | - Kelsey M Kean
- Department of Biochemistry and Biophysics, 2011 Ag & Life Sciences Building, Oregon State University, Corvallis, OR 97331, USA
| | - Lawrence L Hirschberger
- Department of Nutritional Sciences, 227 Savage Hall, Cornell University, Ithaca, NY 14853, USA
| | - Richard B Cooley
- Department of Biochemistry and Biophysics, 2011 Ag & Life Sciences Building, Oregon State University, Corvallis, OR 97331, USA
| | - Martha H Stipanuk
- Department of Nutritional Sciences, 227 Savage Hall, Cornell University, Ithaca, NY 14853, USA.
| | - P Andrew Karplus
- Department of Biochemistry and Biophysics, 2011 Ag & Life Sciences Building, Oregon State University, Corvallis, OR 97331, USA.
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35
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Crowell JK, Sardar S, Hossain MS, Foss FW, Pierce BS. Non-chemical proton-dependent steps prior to O2-activation limit Azotobacter vinelandii 3-mercaptopropionic acid dioxygenase (MDO) catalysis. Arch Biochem Biophys 2016; 604:86-94. [PMID: 27311613 DOI: 10.1016/j.abb.2016.06.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2016] [Revised: 06/09/2016] [Accepted: 06/10/2016] [Indexed: 11/26/2022]
Abstract
3-mercaptopropionate dioxygenase from Azotobacter vinelandii (Av MDO) is a non-heme mononuclear iron enzyme that catalyzes the O2-dependent oxidation of 3-mercaptopropionate (3mpa) to produce 3-sulfinopropionic acid (3spa). With one exception, the active site residues of MDO are identical to bacterial cysteine dioxygenase (CDO). Specifically, the CDO Arg-residue (R50) is replaced by Gln (Q67) in MDO. Despite this minor active site perturbation, substrate-specificity of Av MDO is more relaxed as compared to CDO. In order to investigate the relative timing of chemical and non-chemical events in Av MDO catalysis, the pH/D-dependence of steady-state kinetic parameters (kcat and kcat/KM) and viscosity effects are measured using two different substrates [3mpa and l-cysteine (cys)]. The pL-dependent activity of Av MDO in these reactions can be rationalized assuming a diprotic enzyme model in which three ionic forms of the enzyme are present [cationic, E((z+1)); neutral, E(z); and anionic, E((z-1))]. The activities observed for each substrate appear to be dominated by electrostatic interactions within the enzymatic active site. Given the similarity between MDO and the more extensively characterized mammalian CDO, a tentative model for the role of the conserved 'catalytic triad' is proposed.
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Affiliation(s)
- Joshua K Crowell
- Department of Chemistry & Biochemistry, College of Science, The University of Texas at Arlington, Arlington, TX 76019, USA
| | - Sinjinee Sardar
- Department of Chemistry & Biochemistry, College of Science, The University of Texas at Arlington, Arlington, TX 76019, USA
| | - Mohammad S Hossain
- Department of Chemistry & Biochemistry, College of Science, The University of Texas at Arlington, Arlington, TX 76019, USA
| | - Frank W Foss
- Department of Chemistry & Biochemistry, College of Science, The University of Texas at Arlington, Arlington, TX 76019, USA
| | - Brad S Pierce
- Department of Chemistry & Biochemistry, College of Science, The University of Texas at Arlington, Arlington, TX 76019, USA.
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36
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Wenning L, Stöveken N, Wübbeler JH, Steinbüchel A. Substrate and Cofactor Range Differences of Two Cysteine Dioxygenases from Ralstonia eutropha H16. Appl Environ Microbiol 2016; 82:910-21. [PMID: 26590284 PMCID: PMC4725276 DOI: 10.1128/aem.02568-15] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Accepted: 11/17/2015] [Indexed: 11/20/2022] Open
Abstract
Cysteine dioxygenases (Cdos), which catalyze the sulfoxidation of cysteine to cysteine sulfinic acid (CSA), have been extensively studied in eukaryotes because of their roles in several diseases. In contrast, only a few prokaryotic enzymes of this type have been investigated. In Ralstonia eutropha H16, two Cdo homologues (CdoA and CdoB) have been identified previously. In vivo studies showed that Escherichia coli cells expressing CdoA could convert 3-mercaptopropionate (3MP) to 3-sulfinopropionate (3SP), whereas no 3SP could be detected in cells expressing CdoB. The objective of this study was to confirm these findings and to study both enzymes in detail by performing an in vitro characterization. The proteins were heterologously expressed and purified to apparent homogeneity by immobilized metal chelate affinity chromatography (IMAC). Subsequent analysis of the enzyme activities revealed striking differences with regard to their substrate ranges and their specificities for the transition metal cofactor, e.g., CdoA catalyzed the sulfoxidation of 3MP to a 3-fold-greater extent than the sulfoxidation of cysteine, whereas CdoB converted only cysteine. Moreover, the dependency of the activities of the Cdos from R. eutropha H16 on the metal cofactor in the active center could be demonstrated. The importance of CdoA for the metabolism of the sulfur compounds 3,3'-thiodipropionic acid (TDP) and 3,3'-dithiodipropionic acid (DTDP) by further converting their degradation product, 3MP, was confirmed. Since 3MP can also function as a precursor for polythioester (PTE) synthesis in R. eutropha H16, deletion of cdoA might enable increased synthesis of PTEs.
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Affiliation(s)
- Leonie Wenning
- Institut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität Münster, Münster, Germany
| | - Nadine Stöveken
- Institut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität Münster, Münster, Germany
| | - Jan Hendrik Wübbeler
- Institut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität Münster, Münster, Germany
| | - Alexander Steinbüchel
- Institut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität Münster, Münster, Germany Faculty of Environmental Sciences, King Abdulaziz University, Jeddah, Saudi Arabia
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37
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Goncharenko KV, Seebeck FP. Conversion of a non-heme iron-dependent sulfoxide synthase into a thiol dioxygenase by a single point mutation. Chem Commun (Camb) 2016; 52:1945-8. [DOI: 10.1039/c5cc07772a] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
EgtB from Mycobacterium thermoresistibile catalyzes O2-dependent sulfur–carbon bond formation between the side chains of Nα-trimethyl histidine and γ-glutamyl cysteine as a central step in ergothioneine biosynthesis.
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38
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Pierce BS, Subedi BP, Sardar S, Crowell JK. The "Gln-Type" Thiol Dioxygenase from Azotobacter vinelandii is a 3-Mercaptopropionic Acid Dioxygenase. Biochemistry 2015; 54:7477-90. [PMID: 26624219 DOI: 10.1021/acs.biochem.5b00636] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Cysteine dioxygenase (CDO) is a non-heme iron enzyme that catalyzes the O2-dependent oxidation of l-cysteine to produce cysteinesulfinic acid. Bacterial CDOs have been subdivided as either "Arg-type" or "Gln-type" on the basis of the identity of conserved active site residues. To date, "Gln-type" enzymes remain largely uncharacterized. It was recently noted that the "Gln-type" enzymes are more homologous with another thiol dioxygenase [3-mercaptopropionate dioxygenase (MDO)] identified in Variovorax paradoxus, suggesting that enzymes of the "Gln-type" subclass are in fact MDOs. In this work, a putative "Gln-type" thiol dioxygenase from Azotobacter vinelandii (Av) was purified to homogeneity and characterized. Steady-state assays were performed using three substrates [3-mercaptopropionic acid (3mpa), l-cysteine (cys), and cysteamine (ca)]. Despite comparable maximal velocities, the "Gln-type" Av enzyme exhibited a specificity for 3mpa (kcat/KM = 72000 M(-1) s(-1)) nearly 2 orders of magnitude greater than those for cys (110 M(-1) s(-1)) and ca (11 M(-1) s(-1)). Supporting X-band electron paramagnetic resonance (EPR) studies were performed using nitric oxide (NO) as a surrogate for O2 binding to confirm obligate-ordered addition of substrate prior to NO. Stoichimetric addition of NO to solutions of 3mpa-bound enzyme quantitatively yields an iron-nitrosyl species (Av ES-NO) with EPR features consistent with a mononuclear (S = (3)/2) {FeNO}(7) site. Conversely, two distinct substrate-bound conformations were observed in Av ES-NO samples prepared with cys and ca, suggesting heterogeneous binding within the enzymatic active site. Analytical EPR simulations are provided to establish the relative binding affinity for each substrate (3map > cys > ca). Both kinetic and spectroscopic results presented here are consistent with 3mpa being the preferred substrate for this enzyme.
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Affiliation(s)
- Brad S Pierce
- Department of Chemistry and Biochemistry, College of Sciences, The University of Texas at Arlington , Arlington, Texas 76019, United States
| | - Bishnu P Subedi
- Department of Chemistry and Biochemistry, College of Sciences, The University of Texas at Arlington , Arlington, Texas 76019, United States
| | - Sinjinee Sardar
- Department of Chemistry and Biochemistry, College of Sciences, The University of Texas at Arlington , Arlington, Texas 76019, United States
| | - Joshua K Crowell
- Department of Chemistry and Biochemistry, College of Sciences, The University of Texas at Arlington , Arlington, Texas 76019, United States
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39
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Tchesnokov EP, Fellner M, Siakkou E, Kleffmann T, Martin LW, Aloi S, Lamont IL, Wilbanks SM, Jameson GNL. The cysteine dioxygenase homologue from Pseudomonas aeruginosa is a 3-mercaptopropionate dioxygenase. J Biol Chem 2015; 290:24424-37. [PMID: 26272617 PMCID: PMC4591825 DOI: 10.1074/jbc.m114.635672] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2014] [Revised: 08/02/2015] [Indexed: 02/02/2023] Open
Abstract
Thiol dioxygenation is the initial oxidation step that commits a thiol to important catabolic or biosynthetic pathways. The reaction is catalyzed by a family of specific non-heme mononuclear iron proteins each of which is reported to react efficiently with only one substrate. This family of enzymes includes cysteine dioxygenase, cysteamine dioxygenase, mercaptosuccinate dioxygenase, and 3-mercaptopropionate dioxygenase. Using sequence alignment to infer cysteine dioxygenase activity, a cysteine dioxygenase homologue from Pseudomonas aeruginosa (p3MDO) has been identified. Mass spectrometry of P. aeruginosa under standard growth conditions showed that p3MDO is expressed in low levels, suggesting that this metabolic pathway is available to the organism. Purified recombinant p3MDO is able to oxidize both cysteine and 3-mercaptopropionic acid in vitro, with a marked preference for 3-mercaptopropionic acid. We therefore describe this enzyme as a 3-mercaptopropionate dioxygenase. Mössbauer spectroscopy suggests that substrate binding to the ferrous iron is through the thiol but indicates that each substrate could adopt different coordination geometries. Crystallographic comparison with mammalian cysteine dioxygenase shows that the overall active site geometry is conserved but suggests that the different substrate specificity can be related to replacement of an arginine by a glutamine in the active site.
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Affiliation(s)
| | | | | | - Torsten Kleffmann
- Biochemistry, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand
| | - Lois W Martin
- Biochemistry, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand
| | | | - Iain L Lamont
- Biochemistry, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand
| | - Sigurd M Wilbanks
- Biochemistry, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand
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40
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Gogoi P, Chandravanshi M, Mandal SK, Srivastava A, Kanaujia SP. Heterogeneous behavior of metalloproteins toward metal ion binding and selectivity: insights from molecular dynamics studies. J Biomol Struct Dyn 2015; 34:1470-85. [PMID: 26248730 DOI: 10.1080/07391102.2015.1080629] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
About one-third of the existing proteins require metal ions as cofactors for their catalytic activities and structural complexities. While many of them bind only to a specific metal, others bind to multiple (different) metal ions. However, the exact mechanism of their metal preference has not been deduced to clarity. In this study, we used molecular dynamics (MD) simulations to investigate whether a cognate metal (bound to the structure) can be replaced with other similar metal ions. We have chosen seven different proteins (phospholipase A2, sucrose phosphatase, pyrazinamidase, cysteine dioxygenase (CDO), plastocyanin, monoclonal anti-CD4 antibody Q425, and synaptotagmin 1 C2B domain) bound to seven different divalent metal ions (Ca(2+), Mg(2+), Zn(2+), Fe(2+), Cu(2+), Ba(2+), and Sr(2+), respectively). In total, 49 MD simulations each of 50 ns were performed and each trajectory was analyzed independently. Results demonstrate that in some cases, cognate metal ions can be exchanged with similar metal ions. On the contrary, some proteins show binding affinity specifically to their cognate metal ions. Surprisingly, two proteins CDO and plastocyanin which are known to bind Fe(2+) and Cu(2+), respectively, do not exhibit binding affinity to any metal ion. Furthermore, the study reveals that in some cases, the active site topology remains rigid even without cognate metals, whereas, some require them for their active site stability. Thus, it will be interesting to experimentally verify the accuracy of these observations obtained computationally. Moreover, the study can help in designing novel active sites for proteins to sequester metal ions particularly of toxic nature.
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Affiliation(s)
- Prerana Gogoi
- a Department of Biosciences and Bioengineering , Indian Institute of Technology Guwahati , Guwahati , Assam 781039 , India
| | - Monika Chandravanshi
- a Department of Biosciences and Bioengineering , Indian Institute of Technology Guwahati , Guwahati , Assam 781039 , India
| | - Suraj Kumar Mandal
- a Department of Biosciences and Bioengineering , Indian Institute of Technology Guwahati , Guwahati , Assam 781039 , India
| | - Ambuj Srivastava
- a Department of Biosciences and Bioengineering , Indian Institute of Technology Guwahati , Guwahati , Assam 781039 , India
| | - Shankar Prasad Kanaujia
- a Department of Biosciences and Bioengineering , Indian Institute of Technology Guwahati , Guwahati , Assam 781039 , India
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41
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Alberto ME. A trispyrazolylborato iron cysteinato complex efficiently mimics the cysteine dioxygenation process: mechanistic insights. Chem Commun (Camb) 2015; 51:8369-72. [PMID: 25891839 DOI: 10.1039/c5cc00813a] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The O2 activation process by a CDO biomimetic system has been herein investigated to gain mechanistic details on the unknown reaction mechanism. The outcomes of the DFT study show that the functional model efficiently mimics the enzymatic process, the reaction proceeding with a feasible activation barrier via multistate reactivity patterns.
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Affiliation(s)
- Marta E Alberto
- Dipartimento di Ingegneria Informatica, Modellistica, Elettronica e Sistemistica, Università della Calabria, I-87036 Arcavacata di Rende, Italy.
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42
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A jack-of-all-trades: 2-mercaptosuccinic acid. Appl Microbiol Biotechnol 2015; 99:4545-57. [DOI: 10.1007/s00253-015-6605-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Accepted: 04/11/2015] [Indexed: 12/16/2022]
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43
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Blaesi EJ, Fox BG, Brunold TC. Spectroscopic and Computational Investigation of the H155A Variant of Cysteine Dioxygenase: Geometric and Electronic Consequences of a Third-Sphere Amino Acid Substitution. Biochemistry 2015; 54:2874-84. [PMID: 25897562 DOI: 10.1021/acs.biochem.5b00171] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Cysteine dioxygenase (CDO) is a mononuclear, non-heme iron(II)-dependent enzyme that utilizes molecular oxygen to catalyze the oxidation of l-cysteine (Cys) to cysteinesulfinic acid. Although the kinetic consequences of various outer-sphere amino acid substitutions have previously been assessed, the effects of these substitutions on the geometric and electronic structures of the active site remained largely unexplored. In this work, we have performed a spectroscopic and computational characterization of the H155A CDO variant, which was previously shown to display a rate of Cys oxidation ∼100-fold decreased relative to that of wild-type (WT) CDO. Magnetic circular dichroism and electron paramagnetic resonance spectroscopic data indicate that the His155 → Ala substitution has a significant effect on the electronic structure of the Cys-bound Fe(II)CDO active site. An analysis of these data within the framework of density functional theory calculations reveals that Cys-bound H155A Fe(II)CDO possesses a six-coordinate Fe(II) center, differing from the analogous WT CDO species in the presence of an additional water ligand. The enhanced affinity of the Cys-bound Fe(II) center for a sixth ligand in the H155A CDO variant likely stems from the increased level of conformational freedom of the cysteine-tyrosine cross-link in the absence of the H155 imidazole ring. Notably, the nitrosyl adduct of Cys-bound Fe(II)CDO [which mimics the (O2/Cys)-CDO intermediate] is essentially unaffected by the H155A substitution, suggesting that the primary role played by the H155 side chain in CDO catalysis is to discourage the binding of a water molecule to the Cys-bound Fe(II)CDO active site.
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Affiliation(s)
- Elizabeth J Blaesi
- †Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Brian G Fox
- ‡Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Thomas C Brunold
- †Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
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44
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Sallmann M, Kumar S, Chernev P, Nehrkorn J, Schnegg A, Kumar D, Dau H, Limberg C, de Visser SP. Structure and Mechanism Leading to Formation of the Cysteine Sulfinate Product Complex of a Biomimetic Cysteine Dioxygenase Model. Chemistry 2015; 21:7470-9. [DOI: 10.1002/chem.201500644] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2015] [Indexed: 01/10/2023]
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45
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Harrop TC. New Insights on {FeNO}n (n=7, 8) Systems as Enzyme Models and HNO Donors. ADVANCES IN INORGANIC CHEMISTRY 2015. [DOI: 10.1016/bs.adioch.2014.10.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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46
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Crowell JK, Li W, Pierce BS. Oxidative uncoupling in cysteine dioxygenase is gated by a proton-sensitive intermediate. Biochemistry 2014; 53:7541-8. [PMID: 25387045 DOI: 10.1021/bi501241d] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cysteine dioxygenase (CDO) is a non-heme mononuclear iron enzyme that catalyzes the O2-dependent oxidation of l-cysteine (Cys) to produce cysteine sulfinic acid (CSA). This enzyme catalyzes the first committed step in Cys catabolism; thus, it is central to mammalian sulfur metabolism and redox homeostasis. Ironically, despite nearly 45 years of continued research on CDO, essentially no information has been reported with respect to its kinetic mechanism. In this work, the timing of chemical steps in the CDO kinetic mechanism is investigated by pH/pD-dependent steady-state kinetics and solvent isotope effects on kcat, kcat/KM, and (O2/CSA) coupling. Normal solvent kinetic isotope effects of 1.45 ± 0.05 and 2.0 ± 0.1 are observed in kcat-pL and kcat/KM-pL profiles, respectively. Proton inventory experiments within the pL-independent region (pL 8.5) suggest multiple solvent-exchangeable protons in flight for both kcat and kcat/KM data. The influence of solvent viscosity was also investigated to probe non-chemical steps and to verify that the apparent isotope effects were not attributable to increased solvent viscosity of D2O reactions relative to H2O. Although solvent viscosity did have a modest influence on kcat and kcat/KM, the response is not sufficient to account for the observed solvent isotope effects. This suggests that product release is only partially rate-limiting for CDO catalysis. Most crucially, proton inventory of (O2/CSA) coupling indicates that a proton-sensitive transition state directly follows O2 activation. Thus, protonation of a transient species preceding Cys oxidation is gated by protons in flight. This behavior provides valuable insight into the kinetically masked transients generated during catalysis.
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Affiliation(s)
- Joshua K Crowell
- Department of Chemistry and Biochemistry, College of Sciences, The University of Texas at Arlington , Arlington, Texas 76019, United States
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47
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Davies CG, Fellner M, Tchesnokov EP, Wilbanks SM, Jameson GNL. The Cys-Tyr cross-link of cysteine dioxygenase changes the optimal pH of the reaction without a structural change. Biochemistry 2014; 53:7961-8. [PMID: 25390690 DOI: 10.1021/bi501277a] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Cysteine dioxygenase (CDO) is a non-heme monoiron enzyme with an unusual posttranslational modification in the proximity of the ferrous iron active site. This modification, a cysteine to tyrosine thioether bond, cross-links two β-strands of the β-barrel. We have investigated its role in catalysis through a combined crystallographic and kinetic approach. The C93G variant lacks the cross-link and shows little change in structure from that of the wild type, suggesting that the cross-link does not stabilize an otherwise unfavorable conformation. A pH-dependent kinetic study shows that both cross-linked and un-cross-linked CDO are active but the optimal pH decreases with the presence of the cross-link. This result reflects the effect of the thioether bond on the pKa of Y157 and this residue's role in catalysis. At higher pH values, kcat is also higher for the cross-linked form, extending the pH range of activity. We therefore propose that the cross-link also increases activity by controlling deleterious interactions involving the thiol/ate of C93.
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Affiliation(s)
- Casey G Davies
- Department of Chemistry and MacDiarmid Institute for Advanced Materials and Nanotechnology and ‡Department of Biochemistry, University of Otago , P.O. Box 56, Dunedin 9054, New Zealand
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Li W, Pierce BS. Steady-state substrate specificity and O₂-coupling efficiency of mouse cysteine dioxygenase. Arch Biochem Biophys 2014; 565:49-56. [PMID: 25444857 DOI: 10.1016/j.abb.2014.11.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Revised: 11/07/2014] [Accepted: 11/11/2014] [Indexed: 11/15/2022]
Abstract
Cysteine dioxygenase (CDO) is a non-heme mononuclear iron enzyme that catalyzes the oxygen-dependent oxidation of L-cysteine (Cys) to produce L-cysteine sulfinic acid (CSA). Sequence alignment of mammalian CDO with recently discovered thiol dioxygenase enzymes suggests that the mononuclear iron site within all enzymes in this class share a common 3-His first coordination sphere. This implies a similar mechanistic paradigm among thiol dioxygenase enzymes. Although steady-state studies were first reported for mammalian CDO over 45 years ago, detailed analysis of the specificity for alternative thiol-bearing substrates and their oxidative coupling efficiencies have not been reported for this enzyme. Assuming a similar mechanistic theme among this class of enzymes, characterization of the CDO substrate specificity may provide valuable insight into substrate-active site intermolecular during thiol oxidation. In this work, the substrate-specificity for wild-type Mus musculus CDO was investigated using NMR spectroscopy and LC-MS for a variety of thiol-bearing substrates. Tandem mass spectrometry was used to confirm dioxygenase activity for each non-native substrate investigated. Steady-state Michaelis-Menten parameters for sulfinic acid product formation and O₂-consumption were compared to establish the coupling efficiency for each reaction. In light of these results, the minimal substrate requirements for CDO catalysis and O₂-activation are discussed.
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Affiliation(s)
- Wei Li
- Department of Chemistry and Biochemistry, College of Sciences, The University of Texas at Arlington, Arlington, TX 76019, United States
| | - Brad S Pierce
- Department of Chemistry and Biochemistry, College of Sciences, The University of Texas at Arlington, Arlington, TX 76019, United States.
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Driggers CM, Hartman SJ, Karplus PA. Structures of Arg- and Gln-type bacterial cysteine dioxygenase homologs. Protein Sci 2014; 24:154-61. [PMID: 25307852 DOI: 10.1002/pro.2587] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2014] [Revised: 10/07/2014] [Accepted: 10/09/2014] [Indexed: 11/12/2022]
Abstract
In some bacteria, cysteine is converted to cysteine sulfinic acid by cysteine dioxygenases (CDO) that are only ∼15-30% identical in sequence to mammalian CDOs. Among bacterial proteins having this range of sequence similarity to mammalian CDO are some that conserve an active site Arg residue ("Arg-type" enzymes) and some having a Gln substituted for this Arg ("Gln-type" enzymes). Here, we describe a structure from each of these enzyme types by analyzing structures originally solved by structural genomics groups but not published: a Bacillus subtilis "Arg-type" enzyme that has cysteine dioxygenase activity (BsCDO), and a Ralstonia eutropha "Gln-type" CDO homolog of uncharacterized activity (ReCDOhom). The BsCDO active site is well conserved with mammalian CDO, and a cysteine complex captured in the active site confirms that the cysteine binding mode is also similar. The ReCDOhom structure reveals a new active site Arg residue that is hydrogen bonding to an iron-bound diatomic molecule we have interpreted as dioxygen. Notably, the Arg position is not compatible with the mode of Cys binding seen in both rat CDO and BsCDO. As sequence alignments show that this newly discovered active site Arg is well conserved among "Gln-type" CDO enzymes, we conclude that the "Gln-type" CDO homologs are not authentic CDOs but will have substrate specificity more similar to 3-mercaptopropionate dioxygenases.
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Affiliation(s)
- Camden M Driggers
- Department of Biochemistry and Biophysics, 2011 Ag & Life Sciences Bldg, Oregon State University, Corvallis, Oregon, 97331
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50
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Kabbua T, Anwised P, Boonmee A, Subedi BP, Pierce BS, Thammasirirak S. Autoinduction, purification, and characterization of soluble α-globin chains of crocodile (Crocodylus siamensis) hemoglobin in Escherichia coli. Protein Expr Purif 2014; 103:56-63. [DOI: 10.1016/j.pep.2014.08.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Revised: 08/19/2014] [Accepted: 08/20/2014] [Indexed: 01/30/2023]
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