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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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2
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Duan R, Li J, Liu A. Unveiling the mechanism of cysteamine dioxygenase: A combined HPLC-MS assay and metal-substitution approach. Methods Enzymol 2024; 703:147-166. [PMID: 39260994 DOI: 10.1016/bs.mie.2024.05.018] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/13/2024]
Abstract
Mammalian cysteamine dioxygenase (ADO), a mononuclear non-heme Fe(II) enzyme with three histidine ligands, plays a key role in cysteamine catabolism and regulation of the N-degron signaling pathway. Despite its importance, the catalytic mechanism of ADO remains elusive. Here, we describe an HPLC-MS assay for characterizing thiol dioxygenase catalytic activities and a metal-substitution approach for mechanistic investigation using human ADO as a model. Two proposed mechanisms for ADO differ in oxygen activation: one involving a high-valent ferryl-oxo intermediate. We hypothesized that substituting iron with a metal that has a disfavored tendency to form high-valent states would discriminate between mechanisms. This chapter details the expression, purification, preparation, and characterization of cobalt-substituted ADO. The new HPLC-MS assay precisely measures enzymatic activity, revealing retained reactivity in the cobalt-substituted enzyme. The results obtained favor the concurrent dioxygen transfer mechanism in ADO. This combined approach provides a powerful tool for studying other non-heme iron thiol oxidizing enzymes.
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Affiliation(s)
- Ran Duan
- Department of Chemistry, University of Texas at San Antonio, San Antonio, TX, United States
| | - Jiasong Li
- Department of Chemistry, University of Texas at San Antonio, San Antonio, TX, United States
| | - Aimin Liu
- Department of Chemistry, University of Texas at San Antonio, San Antonio, TX, United States.
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3
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Bennett ZD, Brunold TC. Non-standard amino acid incorporation into thiol dioxygenases. Methods Enzymol 2024; 703:121-145. [PMID: 39260993 PMCID: PMC11391102 DOI: 10.1016/bs.mie.2024.05.022] [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: 09/13/2024]
Abstract
Thiol dioxygenases (TDOs) are non‑heme Fe(II)‑dependent enzymes that catalyze the O2-dependent oxidation of thiol substrates to their corresponding sulfinic acids. Six classes of TDOs have thus far been identified and two, cysteine dioxygenase (CDO) and cysteamine dioxygenase (ADO), are found in eukaryotes. All TDOs belong to the cupin superfamily of enzymes, which share a common β‑barrel fold and two cupin motifs: G(X)5HXH(X)3-6E(X)6G and G(X)5-7PXG(X)2H(X)3N. Crystal structures of TDOs revealed that these enzymes contain a relatively rare, neutral 3‑His iron‑binding facial triad. Despite this shared metal-binding site, TDOs vary greatly in their secondary coordination spheres. Site‑directed mutagenesis has been used extensively to explore the impact of changes in secondary sphere residues on substrate specificity and enzymatic efficiency. This chapter summarizes site-directed mutagenesis studies of eukaryotic TDOs, focusing on the tools and practicality of non‑standard amino acid incorporation.
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Affiliation(s)
- Zachary D Bennett
- 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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4
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Perri M, Licausi F. Thiol dioxygenases: from structures to functions. Trends Biochem Sci 2024; 49:545-556. [PMID: 38622038 DOI: 10.1016/j.tibs.2024.03.007] [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: 11/18/2023] [Revised: 03/07/2024] [Accepted: 03/15/2024] [Indexed: 04/17/2024]
Abstract
Thiol oxidation to dioxygenated sulfinic acid is catalyzed by an enzyme family characterized by a cupin fold. These proteins act on free thiol-containing molecules to generate central metabolism precursors and signaling compounds in bacteria, fungi, and animal cells. In plants and animals, they also oxidize exposed N-cysteinyl residues, directing proteins to proteolysis. Enzyme kinetics, X-ray crystallography, and spectroscopy studies prompted the formulation and testing of hypotheses about the mechanism of action and the different substrate specificity of these enzymes. Concomitantly, the physiological role of thiol dioxygenation in prokaryotes and eukaryotes has been studied through genetic and physiological approaches. Further structural characterization is necessary to enable precise and safe manipulation of thiol dioxygenases (TDOs) for therapeutic, industrial, and agricultural applications.
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Affiliation(s)
- Monica Perri
- Plant Molecular Biology Section, Department of Biology, University of Oxford, Oxford, UK
| | - Francesco Licausi
- Plant Molecular Biology Section, Department of Biology, University of Oxford, Oxford, UK.
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5
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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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6
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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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7
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Lee A, Henderson R, Aylward J, McCombe P. Gut Symptoms, Gut Dysbiosis and Gut-Derived Toxins in ALS. Int J Mol Sci 2024; 25:1871. [PMID: 38339149 PMCID: PMC10856138 DOI: 10.3390/ijms25031871] [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] [Received: 01/04/2024] [Revised: 01/31/2024] [Accepted: 02/01/2024] [Indexed: 02/12/2024] Open
Abstract
Many pathogenetic mechanisms have been proposed for amyotrophic lateral sclerosis (ALS). Recently, there have been emerging suggestions of a possible role for the gut microbiota. Gut microbiota have a range of functions and could influence ALS by several mechanisms. Here, we review the possible role of gut-derived neurotoxins/excitotoxins. We review the evidence of gut symptoms and gut dysbiosis in ALS. We then examine a possible role for gut-derived toxins by reviewing the evidence that these molecules are toxic to the central nervous system, evidence of their association with ALS, the existence of biochemical pathways by which these molecules could be produced by the gut microbiota and existence of mechanisms of transport from the gut to the blood and brain. We then present evidence that there are increased levels of these toxins in the blood of some ALS patients. We review the effects of therapies that attempt to alter the gut microbiota or ameliorate the biochemical effects of gut toxins. It is possible that gut dysbiosis contributes to elevated levels of toxins and that these could potentially contribute to ALS pathogenesis, but more work is required.
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Affiliation(s)
- Aven Lee
- Centre for Clinical Research, The University of Queensland, Brisbane, QLD 4029, Australia; (R.H.); (P.M.)
| | - Robert Henderson
- Centre for Clinical Research, The University of Queensland, Brisbane, QLD 4029, Australia; (R.H.); (P.M.)
- Department of Neurology, Royal Brisbane & Women’s Hospital, Brisbane, QLD 4029, Australia
- Wesley Research Institute, The Wesley Hospital, Auchenflower, QLD 4066, Australia;
| | - James Aylward
- Wesley Research Institute, The Wesley Hospital, Auchenflower, QLD 4066, Australia;
| | - Pamela McCombe
- Centre for Clinical Research, The University of Queensland, Brisbane, QLD 4029, Australia; (R.H.); (P.M.)
- Department of Neurology, Royal Brisbane & Women’s Hospital, Brisbane, QLD 4029, Australia
- Wesley Research Institute, The Wesley Hospital, Auchenflower, QLD 4066, Australia;
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8
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Farman MR, Petráčková D, Kumar D, Držmíšek J, Saha A, Čurnová I, Čapek J, Hejnarová V, Amman F, Hofacker I, Večerek B. Avirulent phenotype promotes Bordetella pertussis adaptation to the intramacrophage environment. Emerg Microbes Infect 2023; 12:e2146536. [PMID: 36357372 PMCID: PMC9858536 DOI: 10.1080/22221751.2022.2146536] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Bordetella pertussis, the causative agent of whooping cough, is an extracellular, strictly human pathogen. However, it has been shown that B. pertussis cells can escape phagocytic killing and survive in macrophages upon internalization. Our time-resolved RNA-seq data suggest that B. pertussis efficiently adapts to the intramacrophage environment and responds to host bactericidal activities. We show that this adaptive response is multifaceted and, surprisingly, related to the BvgAS two-component system, a master regulator of virulence. Our results show that the expression of this regulatory circuit is downregulated upon internalization. Moreover, we demonstrate that the switch to the avirulent Bvg- phase augments a very complex process based on the adjustment of central and energy metabolism, cell wall reinforcement, maintenance of appropriate redox and metal homeostasis, and repair of damaged macromolecules. Nevertheless, not all observed effects could be simply attributed to the transition to Bvg- phase, suggesting that additional regulators are involved in the adaptation to the intramacrophage environment. Interestingly, a large number of genes required for the metabolism of sulphur were strongly modulated within macrophages. In particular, the mutant lacking two genes encoding cysteine dioxygenases displayed strongly attenuated cytotoxicity toward THP-1 cells. Collectively, our results suggest that intracellular B. pertussis cells have adopted the Bvg- mode to acclimate to the intramacrophage environment and respond to antimicrobial activities elicited by THP-1 cells. Therefore, we hypothesize that the avirulent phase represents an authentic phenotype of internalized B. pertussis cells.
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Affiliation(s)
- Mariam R. Farman
- Institute for Theoretical Chemistry, University of Vienna, Vienna, Austria
| | - Denisa Petráčková
- Czech Academy of Sciences, Laboratory of Post-transcriptional Control of Gene Expression, Institute of Microbiology, Prague, Czech Republic
| | - Dilip Kumar
- Czech Academy of Sciences, Laboratory of Post-transcriptional Control of Gene Expression, Institute of Microbiology, Prague, Czech Republic
| | - Jakub Držmíšek
- Czech Academy of Sciences, Laboratory of Post-transcriptional Control of Gene Expression, Institute of Microbiology, Prague, Czech Republic
| | - Argha Saha
- Czech Academy of Sciences, Laboratory of Post-transcriptional Control of Gene Expression, Institute of Microbiology, Prague, Czech Republic
| | - Ivana Čurnová
- Czech Academy of Sciences, Laboratory of Post-transcriptional Control of Gene Expression, Institute of Microbiology, Prague, Czech Republic
| | - Jan Čapek
- Czech Academy of Sciences, Laboratory of Post-transcriptional Control of Gene Expression, Institute of Microbiology, Prague, Czech Republic
| | - Václava Hejnarová
- Czech Academy of Sciences, Laboratory of Post-transcriptional Control of Gene Expression, Institute of Microbiology, Prague, Czech Republic
| | - Fabian Amman
- Institute for Theoretical Chemistry, University of Vienna, Vienna, Austria
| | - Ivo Hofacker
- Institute for Theoretical Chemistry, University of Vienna, Vienna, Austria
| | - Branislav Večerek
- Czech Academy of Sciences, Laboratory of Post-transcriptional Control of Gene Expression, Institute of Microbiology, Prague, Czech Republic, Branislav Večerek Czech Academy of Sciences, Laboratory of Post-transcriptional Control of Gene Expression, Institute of Microbiology, 14220Prague, Czech Republic
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9
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Campillo-Balderas JA, Lazcano A, Cottom-Salas W, Jácome R, Becerra A. Pangenomic Analysis of Nucleo-Cytoplasmic Large DNA Viruses. I: The Phylogenetic Distribution of Conserved Oxygen-Dependent Enzymes Reveals a Capture-Gene Process. J Mol Evol 2023; 91:647-668. [PMID: 37526693 PMCID: PMC10598087 DOI: 10.1007/s00239-023-10126-z] [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] [Received: 07/25/2022] [Accepted: 06/21/2023] [Indexed: 08/02/2023]
Abstract
The Nucleo-Cytoplasmic Large DNA Viruses (NCLDVs) infect a wide range of eukaryotic species, including amoeba, algae, fish, amphibia, arthropods, birds, and mammals. This group of viruses has linear or circular double-stranded DNA genomes whose size spans approximately one order of magnitude, from 100 to 2500 kbp. The ultimate origin of this peculiar group of viruses remains an open issue. Some have argued that NCLDVs' origin may lie in a bacteriophage ancestor that increased its genome size by subsequent recruitment of eukaryotic and bacterial genes. Others have suggested that NCLDVs families originated from cells that underwent an irreversible process of genome reduction. However, the hypothesis that a number of NCLDVs sequences have been recruited from the host genomes has been largely ignored. In the present work, we have performed pangenomic analyses of each of the seven known NCLDVs families. We show that these families' core- and shell genes have cellular homologs, supporting possible escaping-gene events as part of its evolution. Furthermore, the detection of sequences that belong to two protein families (small chain ribonucleotide reductase and Erv1/Air) and to one superfamily [2OG-Fe(II) oxygenases] that are for distribution in all NCLDVs core and shell clusters encoding for oxygen-dependent enzymes suggests that the highly conserved core these viruses originated after the Proterozoic Great Oxidation Event that transformed the terrestrial atmosphere 2.4-2.3 Ga ago.
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Affiliation(s)
- J A Campillo-Balderas
- Facultad de Ciencias, UNAM, Cd. Universitaria, Apdo. Postal 70-407, 04510, Mexico City, DF, Mexico
| | - A Lazcano
- Facultad de Ciencias, UNAM, Cd. Universitaria, Apdo. Postal 70-407, 04510, Mexico City, DF, Mexico
- El Colegio Nacional, Donceles 104, Centro Histórico, 06020, Mexico City, CP, Mexico
| | - W Cottom-Salas
- Facultad de Ciencias, UNAM, Cd. Universitaria, Apdo. Postal 70-407, 04510, Mexico City, DF, Mexico
- Escuela Nacional Preparatoria, Plantel 8 Miguel E. Schulz, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - R Jácome
- Facultad de Ciencias, UNAM, Cd. Universitaria, Apdo. Postal 70-407, 04510, Mexico City, DF, Mexico
| | - A Becerra
- Facultad de Ciencias, UNAM, Cd. Universitaria, Apdo. Postal 70-407, 04510, Mexico City, DF, Mexico.
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10
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Schultz RL, Sabat G, Fox BG, Brunold TC. A Single DNA Point Mutation Leads to the Formation of a Cysteine-Tyrosine Crosslink in the Cysteine Dioxygenase from Bacillus subtilis. Biochemistry 2023; 62:1964-1975. [PMID: 37285547 PMCID: PMC10697556 DOI: 10.1021/acs.biochem.3c00083] [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: 06/09/2023]
Abstract
Cysteine dioxygenase (CDO) is a non-heme iron-containing enzyme that catalyzes the oxidation of cysteine (Cys) to cysteine sulfinic acid (CSA). Crystal structures of eukaryotic CDOs revealed the presence of an unusual crosslink between the sulfur of a cysteine residue (C93 in Mus musculus CDO, MmCDO) and a carbon atom adjacent to the phenyl group of a tyrosine residue (Y157). Formation of this crosslink occurs over time as a byproduct of catalysis and increases the catalytic efficiency of CDO by at least 10-fold. Interestingly, in bacterial CDOs, the residue corresponding to C93 is replaced by a highly conserved glycine (G82 in Bacillus subtilis CDO, BsCDO), which precludes the formation of a C-Y crosslink in these enzymes; yet bacterial CDOs achieve turnover rates paralleling those of fully crosslinked eukaryotic CDOs. In the present study, we prepared the G82C variant of BsCDO to determine if a single DNA point mutation could lead to C-Y crosslink formation in this enzyme. We used gel electrophoresis, peptide mass spectrometry, electron paramagnetic resonance spectroscopy, and kinetic assays to characterize this variant alongside the natively crosslinked wild-type (WT) MmCDO and the natively non-crosslinked WT BsCDO. Collectively, our results provide compelling evidence that the G82C BsCDO variant is indeed capable of C-Y crosslink formation. Our kinetic studies indicate that G82C BsCDO has a reduced catalytic efficiency compared to WT BsCDO and that activity increases as the ratio of crosslinked to non-crosslinked enzyme increases. Finally, by carrying out a bioinformatic analysis of the CDO family, we were able to identify a large number of putatively crosslinked bacterial CDOs, the majority of which are from Gram-negative pathogenic bacteria.
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Affiliation(s)
- Rebecca L. Schultz
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Grzegorz Sabat
- Mass Spectrometry Core, Biotechnology Center, 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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11
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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: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [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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12
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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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13
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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: 7] [Impact Index Per Article: 3.5] [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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Abstract
Here, the choice of the first coordination shell of the metal center is analyzed from the perspective of charge maintenance in a binary enzyme-substrate complex and an O2-bound ternary complex in the nonheme iron oxygenases. Comparing homogentisate 1,2-dioxygenase and gentisate dioxygenase highlights the significance of charge maintenance after substrate binding as an important factor that drives the reaction coordinate. We then extend the charge analysis to several common types of nonheme iron oxygenases containing either a 2-His-1-carboxylate facial triad or a 3-His or 4-His ligand motif, including extradiol and intradiol ring-cleavage dioxygenases, thiol dioxygenases, α-ketoglutarate-dependent oxygenases, and carotenoid cleavage oxygenases. After forming the productive enzyme-substrate complex, the overall charge of the iron complex at the 0, +1, or +2 state is maintained in the remaining catalytic steps. Hence, maintaining a constant charge is crucial to promote the reaction of the iron center beginning from the formation of the Michaelis or ternary complex. The charge compensation to the iron ion is tuned not only by protein-derived carboxylate ligands but also by substrates. Overall, these analyses indicate that charge maintenance at the iron center is significant when all the necessary components form a productive complex. This charge maintenance concept may apply to most oxygen-activating metalloenzymes systems that do not draw electrons and protons step-by-step from a separate reactant, such as NADH, via a reductase. The charge maintenance perception may also be useful in proposing catalytic pathways or designing prototypical reactions using artificial or engineered enzymes for biotechnological applications.
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Affiliation(s)
- Ephrahime S. Traore
- Department of Chemistry, The University of Texas at San Antonio, San Antonio, Texas 78249, United States
| | - Aimin Liu
- Department of Chemistry, The University of Texas at San Antonio, San Antonio, Texas 78249, United States
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15
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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: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [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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16
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Tariq M, Ozbek P, Moin ST. Hydration modulates oxygen channel residues for oxygenation of cysteine dioxygenase: Perspectives from molecular dynamics simulations. J Mol Graph Model 2021; 110:108060. [PMID: 34768230 DOI: 10.1016/j.jmgm.2021.108060] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Revised: 10/25/2021] [Accepted: 10/25/2021] [Indexed: 11/26/2022]
Abstract
Cysteine dioxygenase (CDO) regulates the concentration of l-cysteine substrate by its oxidation in the body to prevent different diseases, including neurodegenerative and autoimmune diseases. CDO catalyzes the oxidation of thiol group of l-cysteine to l-cysteine sulfinic acid using molecular oxygen. In this study, molecular dynamics simulations were applied to ligand-free CDO, cysteine-bound CDO, and oxygen-bound CDO-cysteine complex which were primarily subjected to the evaluation of their structural and dynamical properties. The simulation data provided significant information not only on the conformational changes of the enzyme after its ligation but also on the co-ligation by sequential binding of l-cysteine and molecular oxygen. It was found that the ligation and co-ligation perturbed the active site region as well as the overall protein dynamics which were analyzed in terms of root mean square deviation, root mean square fluctuation and dynamic cross correlation matrices as well as principal component analysis. Furthermore, oxygen transport pathways were successfully explored by taking various tunnel clusters into account and one of those clusters was given preference based on the throughput value. The bottleneck formed by different amino acid residues was examined to figure out their role in the oxygenation process of the enzyme. The residues forming the tunnel's bottleneck and their dynamics mediated by water molecules were further investigated using radial distribution functions which gave insights into the hydration behavior of these residues. The findings based on the hydration behavior in turn served to explore the water-mediated dynamics of these residues in the modulation of the pathway, including tunnel gating for the oxygen entry and diffusion to the active site, which is essential for the CDO's catalytic function.
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Affiliation(s)
- Muhammad Tariq
- Third World Center for Science and Technology, H.E.J. Research Institute of Chemistry, International Center for Chemical and Biological Sciences, University of Karachi, Karachi, 75270, Pakistan
| | - Pemra Ozbek
- Department of Bioengineering, Faculty of Engineering, Marmara University, Istanbul, 34722, Turkey.
| | - Syed Tarique Moin
- Third World Center for Science and Technology, H.E.J. Research Institute of Chemistry, International Center for Chemical and Biological Sciences, University of Karachi, Karachi, 75270, Pakistan.
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17
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Wang Y, Shin I, Li J, Liu A. Crystal structure of human cysteamine dioxygenase provides a structural rationale for its function as an oxygen sensor. J Biol Chem 2021; 297:101176. [PMID: 34508780 PMCID: PMC8503633 DOI: 10.1016/j.jbc.2021.101176] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Revised: 09/03/2021] [Accepted: 09/05/2021] [Indexed: 01/03/2023] Open
Abstract
Cysteamine dioxygenase (ADO) plays a vital role in regulating thiol metabolism and preserving oxygen homeostasis in humans by oxidizing the sulfur of cysteamine and N-terminal cysteine-containing proteins to their corresponding sulfinic acids using O2 as a cosubstrate. However, as the only thiol dioxygenase that processes both small-molecule and protein substrates, how ADO handles diverse substrates of disparate sizes to achieve various reactions is not understood. The knowledge gap is mainly due to the three-dimensional structure not being solved, as ADO cannot be directly compared with other known thiol dioxygenases. Herein, we report the first crystal structure of human ADO at a resolution of 1.78 Å with a nickel-bound metal center. Crystallization was achieved through both metal substitution and C18S/C239S double mutations. The metal center resides in a tunnel close to an entry site flanked by loops. While ADO appears to use extensive flexibility to handle substrates of different sizes, it also employs proline and proline pairs to maintain the core protein structure and to retain the residues critical for catalysis in place. This feature distinguishes ADO from thiol dioxygenases that only oxidize small-molecule substrates, possibly explaining its divergent substrate specificity. Our findings also elucidate the structural basis for ADO functioning as an oxygen sensor by modifying N-degron substrates to transduce responses to hypoxia. Thus, this work fills a gap in structure–function relationships of the thiol dioxygenase family and provides a platform for further mechanistic investigation and therapeutic intervention targeting impaired oxygen sensing.
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Affiliation(s)
- Yifan Wang
- Department of Chemistry, The University of Texas at San Antonio, Texas, USA
| | - Inchul Shin
- Department of Chemistry, The University of Texas at San Antonio, Texas, USA
| | - Jiasong Li
- Department of Chemistry, The University of Texas at San Antonio, Texas, USA
| | - Aimin Liu
- Department of Chemistry, The University of Texas at San Antonio, Texas, USA.
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18
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Lee A, Arachchige BJ, Henderson R, Aylward J, McCombe PA. Elevated Levels of Homocysteinesulfinic Acid in the Plasma of Patients with Amyotrophic Lateral Sclerosis: A Potential Source of Excitotoxicity? NEURODEGENER DIS 2021; 20:200-206. [PMID: 34348328 DOI: 10.1159/000517964] [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: 03/26/2021] [Accepted: 06/03/2021] [Indexed: 11/19/2022] Open
Abstract
OBJECTIVES Excitotoxicity is thought to be involved in the pathogenesis of amyotrophic lateral sclerosis (ALS). One possible source of excitotoxicity is the presence of sulphur amino acids (SAAs). In the brain of subjects with ALS, there are increased levels of taurine. In the metabolism of methionine to taurine, excitatory sulphur amino acids (SAAs) are formed. These could potentially contribute to excitotoxicity in ALS. The present study has examined whether plasma levels of SAAs in 38 ALS patients differ from those of 30 healthy controls. METHODS Plasma levels of SAAs were measured by liquid chromatography mass spectrometry. RESULTS There were no significant changes in plasma cysteic acid, cysteine sulfinic acid, and homocysteic acid in ALS patients compared to healthy subjects. Significant elevations in plasma homocysteinesulfinic acid (HCSA) levels (p < 0.0001) were observed in the ALS patients (75.91 ± 15.38 nM) compared to healthy controls (54.06 ± 8.503 nM); 50% of the ALS patients had HCSA levels that were 1.5-2-folds higher than those of controls. Plasma levels of HCSA differed significantly (p = 0.0440) between patients with bulbar onset and spinal onset (68.57 ± 14.20 vs. 79.30 ± 14.95 nM, respectively). CONCLUSION HCSA is elevated in the blood of subjects with ALS. Since HCSA can be transported from the blood to the CNS by active transport, has neurotransmitter properties, and can activate synaptic receptors including NMDAR and metabotropic glutamate receptor, it is possible that increases in HCSA could influence glutamatergic neurotransmission and potentially contribute to excitotoxicity in some ALS patients.
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Affiliation(s)
- Aven Lee
- Centre for Clinical Research, The University of Queensland, Brisbane, Queensland, Australia
| | - Buddhika Jayakody Arachchige
- Mass Spectrometry Facility, Centre for Clinical Research, The University of Queensland, Brisbane, Queensland, Australia
| | - Robert Henderson
- Department of Neurology, Royal Brisbane & Women's Hospital, Brisbane, Queensland, Australia
| | - James Aylward
- Wesley Medical Research, The Wesley Hospital, Auchenflower, Queensland, Australia
| | - Pamela Ann McCombe
- Centre for Clinical Research, The University of Queensland, Brisbane, Queensland, Australia.,Wesley Medical Research, The Wesley Hospital, Auchenflower, Queensland, Australia
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19
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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: 12] [Impact Index Per Article: 4.0] [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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20
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Goff JL, Schaefer JK, Yee N. Extracellular sulfite is protective against reactive oxygen species and antibiotic stress in Shewanella oneidensis MR-1. ENVIRONMENTAL MICROBIOLOGY REPORTS 2021; 13:394-400. [PMID: 33870629 DOI: 10.1111/1758-2229.12947] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Accepted: 04/04/2021] [Indexed: 06/12/2023]
Abstract
In this study, we investigated the extracellular reactive sulfur species produced by Shewanella oneidensis MR-1 during growth. The results showed that sulfite is the major extracellular sulfur metabolite released to the growth medium under both aerobic and anaerobic growth conditions. Exogenous sulfite at physiological concentrations protected S. oneidensis MR-1 from hydrogen peroxide toxicity and enhanced tolerance to the beta-lactam antibiotics cefazolin, meropenem, doripenem and ertapenem. These findings suggest that the release of extracellular sulfite is a bacterial defence mechanism that plays a role in the mitigation of environmental stress.
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Affiliation(s)
- Jennifer L Goff
- Department of Earth and Planetary Sciences, Rutgers University, Piscataway, NJ, USA
| | - Jeffra K Schaefer
- Department of Environmental Sciences, Rutgers University, New Brunswick, NJ, USA
| | - Nathan Yee
- Department of Earth and Planetary Sciences, Rutgers University, Piscataway, NJ, USA
- Department of Environmental Sciences, Rutgers University, New Brunswick, NJ, USA
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21
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He Z, Liu Z, Gong L. Biomarker identification and pathway analysis of rheumatoid arthritis based on metabolomics in combination with ingenuity pathway analysis. Proteomics 2021; 21:e2100037. [PMID: 33969925 DOI: 10.1002/pmic.202100037] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Revised: 04/30/2021] [Accepted: 04/30/2021] [Indexed: 12/19/2022]
Abstract
Rheumatoid arthritis (RA) is a common autoimmune and inflammatory disease worldwide, but understanding its pathogenesis is still limited. In this study, plasma untargeted metabolomics of a discovery cohort and targeted analysis of a verification cohort were performed by gas chromatograph mass spectrometry (GC/MS). Univariate and multivariate statistical analysis were utilized to reveal differential metabolites, followed by the construction of biomarker panel through random forest (RF) algorithm. The pathways involved in RA were enriched by differential metabolites using Ingenuity Pathway Analysis (IPA) suite. Untargeted metabolomics revealed eighteen significantly altered metabolites in RA. Among these metabolites, a three-metabolite marker panel consisting of L-cysteine, citric acid and L-glutamine was constructed, using random forest algorithm that could predict RA with high accuracy, sensitivity and specificity based on a multivariate exploratory receiver operator characteristic (ROC) curve analysis. The panel was further validated by support vector machine (SVM) and partial least squares discriminant analysis (PLS-DA) algorithms, and also verified with targeted metabolomics using a verification cohort. Additionally, the dysregulated taurine biosynthesis pathway in RA was revealed by an integrated analysis of metabolomics and transcriptomics. Our findings in this study not only provided a mechanism underlying RA pathogenesis, but also offered alternative therapeutic targets for RA.
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Affiliation(s)
- Zhuoru He
- International Institute for Translational Chinese Medicine, Guangzhou University of Chinese Medicine, Guangzhou, Guangdong, 510006, PR China
| | - Zhongqiu Liu
- International Institute for Translational Chinese Medicine, Guangzhou University of Chinese Medicine, Guangzhou, Guangdong, 510006, PR China
| | - Lingzhi Gong
- International Institute for Translational Chinese Medicine, Guangzhou University of Chinese Medicine, Guangzhou, Guangdong, 510006, PR China
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22
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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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23
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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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24
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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: 21] [Impact Index Per Article: 5.3] [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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25
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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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26
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Li ZW, Liang S, Ke Y, Deng JJ, Zhang MS, Lu DL, Li JZ, Luo XC. The feather degradation mechanisms of a new Streptomyces sp. isolate SCUT-3. Commun Biol 2020; 3:191. [PMID: 32332852 PMCID: PMC7181669 DOI: 10.1038/s42003-020-0918-0] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Accepted: 03/30/2020] [Indexed: 01/08/2023] Open
Abstract
Feather waste is the highest protein-containing resource in nature and is poorly reused. Bioconversion is widely accepted as a low-cost and environmentally benign process, but limited by the availability of safe and highly efficient feather degrading bacteria (FDB) for its industrial-scale fermentation. Excessive focuses on keratinase and limited knowledge of other factors have hindered complete understanding of the mechanisms employed by FDB to utilize feathers and feather cycling in the biosphere. Streptomyces sp. SCUT-3 can efficiently degrade feather to products with high amino acid content, useful as a nutrition source for animals, plants and microorganisms. Using multiple omics and other techniques, we reveal how SCUT-3 turns on its feather utilization machinery, including its colonization, reducing agent and protease secretion, peptide/amino acid importation and metabolism, oxygen consumption and iron uptake, spore formation and resuscitation, and so on. This study would shed light on the feather utilization mechanisms of FDBs. Li et a. report a new Streptromyces isolate, SCUT-3 which can efficiently degrade feather into products with high amino acid content, useful as feed for plants, animals and microbes. Using multiple omics and other techniques, they report how SCUT-3 turns on its feather utilization machinery and suggest a number of expressed genes most likely implicated in feather degradation.
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Affiliation(s)
- Zhi-Wei Li
- School of Biology and Biological Engineering, South China University of Technology, Guangzhou, Guangdong, P. R. China
| | - Shuang Liang
- School of Biology and Biological Engineering, South China University of Technology, Guangzhou, Guangdong, P. R. China
| | - Ye Ke
- Yingdong College of Life Sciences, Shaoguan University, Shaoguan, Guangdong, P. R. China
| | - Jun-Jin Deng
- School of Biology and Biological Engineering, South China University of Technology, Guangzhou, Guangdong, P. R. China
| | - Ming-Shu Zhang
- School of Biology and Biological Engineering, South China University of Technology, Guangzhou, Guangdong, P. R. China
| | - De-Lin Lu
- School of Biology and Biological Engineering, South China University of Technology, Guangzhou, Guangdong, P. R. China
| | - Jia-Zhou Li
- Zhanjiang Ocean Sciences and Technologies Research Co. LTD, Zhanjiang, Guangdong, P. R. China
| | - Xiao-Chun Luo
- School of Biology and Biological Engineering, South China University of Technology, Guangzhou, Guangdong, P. R. China.
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27
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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: 10] [Impact Index Per Article: 2.0] [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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28
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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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29
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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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30
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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: 27] [Impact Index Per Article: 5.4] [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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31
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Kregiel D, Rygala A, Kolesinska B, Nowacka M, Herc AS, Kowalewska A. Antimicrobial and Antibiofilm N-acetyl-L-cysteine Grafted Siloxane Polymers with Potential for Use in Water Systems. Int J Mol Sci 2019; 20:E2011. [PMID: 31022884 PMCID: PMC6515369 DOI: 10.3390/ijms20082011] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Revised: 04/16/2019] [Accepted: 04/22/2019] [Indexed: 01/28/2023] Open
Abstract
Antibiofilm strategies may be based on the prevention of initial bacterial adhesion, the inhibition of biofilm maturation or biofilm eradication. N-acetyl-L-cysteine (NAC), widely used in medical treatments, offers an interesting approach to biofilm destruction. However, many Eubacteria strains are able to enzymatically decompose the NAC molecule. This is the first report on the action of two hybrid materials, NAC-Si-1 and NAC-Si-2, against bacteria isolated from a water environment: Agrobacterium tumefaciens, Aeromonas hydrophila, Citrobacter freundii, Enterobacter soli, Janthinobacterium lividum and Stenotrophomonas maltophilia. The NAC was grafted onto functional siloxane polymers to reduce its availability to bacterial enzymes. The results confirm the bioactivity of NAC. However, the final effect of its action was environment- and strain-dependent. Moreover, all the tested bacterial strains showed the ability to degrade NAC by various metabolic routes. The NAC polymers were less effective bacterial inhibitors than NAC, but more effective at eradicating mature bacterial biofilms.
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Affiliation(s)
- Dorota Kregiel
- Institute of Fermentation Technology and Microbiology, Lodz University of Technology, Wolczanska 171/173, 90-924 Lodz, Poland.
| | - Anna Rygala
- Institute of Fermentation Technology and Microbiology, Lodz University of Technology, Wolczanska 171/173, 90-924 Lodz, Poland.
| | - Beata Kolesinska
- Institute of Organic Chemistry, Faculty of Chemistry, Lodz University of Technology, Zeromskiego 116, 90-924 Lodz, Poland.
| | - Maria Nowacka
- Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Sienkiewicza 112, 90-363 Lodz, Poland.
| | - Agata S Herc
- Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Sienkiewicza 112, 90-363 Lodz, Poland.
| | - Anna Kowalewska
- Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Sienkiewicza 112, 90-363 Lodz, Poland.
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32
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Mitchell AJ, Weng JK. Unleashing the Synthetic Power of Plant Oxygenases: From Mechanism to Application. PLANT PHYSIOLOGY 2019; 179:813-829. [PMID: 30670605 PMCID: PMC6393811 DOI: 10.1104/pp.18.01223] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Accepted: 01/14/2019] [Indexed: 05/23/2023]
Abstract
The functions and biochemical mechanisms of major classes of plant oxygenases are discussed, and their potential utility for plant synthetic biology is explored.
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Affiliation(s)
- Andrew J Mitchell
- Whitehead Institute for Biomedical Research, Cambridge, Massachusetts 02142
| | - Jing-Ke Weng
- Whitehead Institute for Biomedical Research, Cambridge, Massachusetts 02142
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
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33
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Brandt U, Galant G, Meinert-Berning C, Steinbüchel A. Functional analysis of active amino acid residues of the mercaptosuccinate dioxygenase of Variovorax paradoxus B4. Enzyme Microb Technol 2018; 120:61-68. [PMID: 30396400 DOI: 10.1016/j.enzmictec.2018.09.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2018] [Revised: 08/23/2018] [Accepted: 09/20/2018] [Indexed: 01/20/2023]
Abstract
Thiol dioxygenases are non-heme mononuclear-iron proteins and belong to the cupin superfamily. In 2014, mercaptosuccinate dioxygenase (Msdo) of Variovorax paradoxus B4 was identified as another bacterial cysteine dioxygenase (Cdo) homolog catalyzing the conversion of mercaptosuccinate (MS) into succinate and sulfite. To gain further insights into potentially important amino acid residues for enzyme activity, seven enzyme variants were generated and analyzed. (i) Three variants comprised the substitution of one conserved histidine residue each by leucine, either supposed to be mandatory for coordination of the Fe(II) cofactor (H93 and H95) or to be important for substrate positioning within the active site (H163). The corresponding enzyme variants were completely inactive confirming their essential roles for enzyme activity. (ii) Mutation C100S resulted as well in an inactive enzyme demonstrating its importance for either stability or activity of the protein. (iii) For eukaryotic Cdo, a hydrogen bond network for substrate positioning was postulated, and the corresponding amino acids are basically present in Msdo. Albeit the MsdoQ64A mutation exhibited an increased Km of 0.29 mM when compared to the wildtype with 0.06 mM, it did not significantly affect the specific activity. (iv) The variant MsdoR66A showed only very low activity even when high amounts of enzyme were applied indicating that this residue might be important for catalysis. (v) No strong effect had the mutation Y165F for which a specific enzyme activity of 10.22 μmol min-1 mg-1 protein and a Km value of 0.06 mM with high similarity to those of the wildtype enzyme were obtained. This residue corresponds to Y157 of human Cdo, which is part of the catalytic triad and is supposed to be involved in substrate positioning. Apparently, another residue could fulfill this role in Msdo, since the loss of Y165 did not have a strong effect.
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Affiliation(s)
- Ulrike Brandt
- Institut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität, D-48149 Münster, Germany
| | - Gulsina Galant
- Institut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität, D-48149 Münster, Germany
| | - Christina Meinert-Berning
- Institut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität, D-48149 Münster, Germany
| | - Alexander Steinbüchel
- Institut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität, D-48149 Münster, Germany; Environmental Science Department, King Abdulaziz University, Jeddah, Saudi Arabia.
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34
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Giuntoli B, Perata P. Group VII Ethylene Response Factors in Arabidopsis: Regulation and Physiological Roles. PLANT PHYSIOLOGY 2018; 176:1143-1155. [PMID: 29269576 PMCID: PMC5813551 DOI: 10.1104/pp.17.01225] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Accepted: 12/19/2017] [Indexed: 05/19/2023]
Abstract
The role of ERF-VII TFs in higher plants is to coordinate their signature response to oxygen deficiency, but additional layers of modulation of ERF-VII activity enrich their regulatory range.
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Affiliation(s)
- Beatrice Giuntoli
- Plantlab, Institute of Life Sciences, Scuola superiore Sant'Anna, Via Guidiccioni 8/10, 56017 Pisa, Italy
- Department of Biology, University of Pisa, Via Ghini 13, 56126 Pisa, Italy
| | - Pierdomenico Perata
- Plantlab, Institute of Life Sciences, Scuola superiore Sant'Anna, Via Guidiccioni 8/10, 56017 Pisa, Italy
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35
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Pietra F. On the Dynamical Behavior of the Cysteine Dioxygenase-l-Cysteine Complex in the Presence of Free Dioxygen and l-Cysteine. Chem Biodivers 2017; 14. [PMID: 28857465 DOI: 10.1002/cbdv.201700290] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Accepted: 08/23/2017] [Indexed: 11/11/2022]
Abstract
In this work, viable models of cysteine dioxygenase (CDO) and its complex with l-cysteine dianion were built for the first time, under strict adherence to the crystal structure from X-ray diffraction studies, for all atom molecular dynamics (MD). Based on the CHARMM36 FF, the active site, featuring an octahedral dummy Fe(II) model, allowed us observing water exchange, which would have escaped attention with the more popular bonded models. Free dioxygen (O2 ) and l-cysteine, added at the active site, could be observed being expelled toward the solvating medium under Random Accelerated Molecular Dynamics (RAMD) along major and minor pathways. Correspondingly, free dioxygen (O2 ), added to the solvating medium, could be observed to follow the same above pathways in getting to the active site under unbiased MD. For the bulky l-cysteine, 600 ns of trajectory were insufficient for protein penetration, and the molecule was stuck at the protein borders. These models pave the way to free energy studies of ligand associations, devised to better clarify how this cardinal enzyme behaves in human metabolism.
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Affiliation(s)
- Francesco Pietra
- Accademia Lucchese di Scienze, Lettere e Arti, Classe di Scienze, Palazzo Pretorio, via Vittorio Veneto 1, 55100, Lucca, Italy
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36
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Ordóñez-Robles M, Santos-Beneit F, Albillos SM, Liras P, Martín JF, Rodríguez-García A. Streptomyces tsukubaensis as a new model for carbon repression: transcriptomic response to tacrolimus repressing carbon sources. Appl Microbiol Biotechnol 2017; 101:8181-8195. [PMID: 28983826 DOI: 10.1007/s00253-017-8545-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Revised: 09/16/2017] [Accepted: 09/18/2017] [Indexed: 11/26/2022]
Abstract
In this work, we identified glucose and glycerol as tacrolimus repressing carbon sources in the important species Streptomyces tsukubaensis. A genome-wide analysis of the transcriptomic response to glucose and glycerol additions was performed using microarray technology. The transcriptional time series obtained allowed us to compare the transcriptomic profiling of S. tsukubaensis growing under tacrolimus producing and non-producing conditions. The analysis revealed important and different metabolic changes after the additions and a lack of transcriptional activation of the fkb cluster. In addition, we detected important differences in the transcriptional response to glucose between S. tsukubaensis and the model species Streptomyces coelicolor. A number of genes encoding key players of morphological and biochemical differentiation were strongly and permanently downregulated by the carbon sources. Finally, we identified several genes showing transcriptional profiles highly correlated to that of the tacrolimus biosynthetic pathway regulator FkbN that might be potential candidates for the improvement of tacrolimus production.
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Affiliation(s)
- María Ordóñez-Robles
- Área de Microbiología, Facultad de Ciencias Biológicas y Ambientales, Universidad de León, 24071, León, Spain
- Instituto de Biotecnología de León, INBIOTEC, Avda. Real no. 1, 24006, León, Spain
| | - Fernando Santos-Beneit
- Instituto de Biotecnología de León, INBIOTEC, Avda. Real no. 1, 24006, León, Spain
- Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Medical School, Newcastle University, Newcastle upon Tyne, UK
| | - Silvia M Albillos
- Instituto de Biotecnología de León, INBIOTEC, Avda. Real no. 1, 24006, León, Spain
- Departamento de Biotecnología y Ciencia de los Alimentos, Facultad de Ciencias, Universidad de Burgos, 09001, Burgos, Spain
| | - Paloma Liras
- Área de Microbiología, Facultad de Ciencias Biológicas y Ambientales, Universidad de León, 24071, León, Spain
- Instituto de Biotecnología de León, INBIOTEC, Avda. Real no. 1, 24006, León, Spain
| | - Juan F Martín
- Área de Microbiología, Facultad de Ciencias Biológicas y Ambientales, Universidad de León, 24071, León, Spain
- Instituto de Biotecnología de León, INBIOTEC, Avda. Real no. 1, 24006, León, Spain
| | - Antonio Rodríguez-García
- Área de Microbiología, Facultad de Ciencias Biológicas y Ambientales, Universidad de León, 24071, León, Spain.
- Instituto de Biotecnología de León, INBIOTEC, Avda. Real no. 1, 24006, León, Spain.
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37
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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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38
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Dimitrova NH, Dermen IA, Todorova ND, Vasilev KG, Dimitrov SD, Mekenyan OG, Ikenaga Y, Aoyagi T, Zaitsu Y, Hamaguchi C. CATALOGIC 301C model - validation and improvement. SAR AND QSAR IN ENVIRONMENTAL RESEARCH 2017; 28:511-524. [PMID: 28728491 DOI: 10.1080/1062936x.2017.1343255] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Accepted: 06/13/2017] [Indexed: 06/07/2023]
Abstract
In Europe, REACH legislation encourages the use of alternative in silico methods such as (Q)SAR models. According to the recent progress of Chemical Substances Control Law (CSCL) in Japan, (Q)SAR predictions are also utilized as supporting evidence for the assessment of bioaccumulation potential of chemicals along with read across. Currently, the effective use of read across and QSARs is examined for other hazards, including biodegradability. This paper describes the results of external validation and improvement of CATALOGIC 301C model based on more than 1000 tested new chemical substances of the publication schedule under CSCL. CATALOGIC 301C model meets all REACH requirements to be used for biodegradability assessment. The model formalism built on scientific understanding for the microbial degradation of chemicals has a well-defined and transparent applicability domain. The model predictions are adequate for the evaluation of the ready degradability of chemicals.
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Affiliation(s)
- N H Dimitrova
- a Laboratory of Mathematical Chemistry , University "Prof. As. Zlatarov" , Bourgas , Bulgaria
| | - I A Dermen
- a Laboratory of Mathematical Chemistry , University "Prof. As. Zlatarov" , Bourgas , Bulgaria
| | - N D Todorova
- a Laboratory of Mathematical Chemistry , University "Prof. As. Zlatarov" , Bourgas , Bulgaria
| | - K G Vasilev
- a Laboratory of Mathematical Chemistry , University "Prof. As. Zlatarov" , Bourgas , Bulgaria
| | - S D Dimitrov
- a Laboratory of Mathematical Chemistry , University "Prof. As. Zlatarov" , Bourgas , Bulgaria
| | - O G Mekenyan
- a Laboratory of Mathematical Chemistry , University "Prof. As. Zlatarov" , Bourgas , Bulgaria
| | - Y Ikenaga
- b Chemical Management Center, National Institute of Technology and Evaluation (NITE) , Japan
| | - T Aoyagi
- b Chemical Management Center, National Institute of Technology and Evaluation (NITE) , Japan
| | - Y Zaitsu
- b Chemical Management Center, National Institute of Technology and Evaluation (NITE) , Japan
| | - C Hamaguchi
- b Chemical Management Center, National Institute of Technology and Evaluation (NITE) , Japan
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39
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Sarkar B, Kulharia M, Mantha AK. Understanding human thiol dioxygenase enzymes: structure to function, and biology to pathology. Int J Exp Pathol 2017; 98:52-66. [PMID: 28439920 DOI: 10.1111/iep.12222] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Accepted: 01/18/2017] [Indexed: 12/15/2022] Open
Abstract
Amino acid metabolism is a significant metabolic activity in humans, especially of sulphur-containing amino acids, methionine and cysteine (Cys). Cys is cytotoxic and neurotoxic in nature; hence, mammalian cells maintain a constant intracellular level of Cys. Metabolism of Cys is mainly regulated by two thiol dioxygenases: cysteine dioxygenase (CDO) and 2-aminoethanethiol dioxygenase (ADO). CDO and ADO are the only human thiol dioxygenases reported with a role in Cys metabolism and localized to mitochondria. This metabolic pathway is important in various human disorders, as it is responsible for the synthesis of antioxidant glutathione and is also for the synthesis of hypotaurine and taurine. CDO is the most extensively studied protein, whose high-resolution crystallographic structures have been solved. As compared to CDO, ADO is less studied, even though it has a key role in cysteamine metabolism. To further understand ADO's structure and function, the three-dimensional structures have been predicted from I-TASSER and SWISS-MODEL servers and validated with PROCHECK software. Structural superimposition approach using iPBA web server further confirmed near-identical structures (including active sites) for the predicted protein models of ADO as compared to CDO. In addition, protein-protein interaction and their association in patho-physiology are crucial in understanding protein functions. Both ADO and CDO interacting partner profiles have been presented using STRING database. In this study, we have predicted a 3D model structure for ADO and summarized the biological roles and the pathological consequences which are associated with the altered expression and functioning of ADO and CDO in case of cancer, neurodegenerative disorders and other human diseases.
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Affiliation(s)
- Bibekananda Sarkar
- Center for Animal Sciences, School of Basic and Applied Sciences, Central University of Punjab, Bathinda, Punjab, India
| | - Mahesh Kulharia
- Center for Computational Sciences, School of Basic and Applied Sciences, Central University of Punjab, Bathinda, Punjab, India
| | - Anil K Mantha
- Center for Animal Sciences, School of Basic and Applied Sciences, Central University of Punjab, Bathinda, Punjab, India
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40
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Andreeßen C, Gerlt V, Steinbüchel A. Conversion of cysteine to 3‐mercaptopyruvic acid by bacterial aminotransferases. Enzyme Microb Technol 2017; 99:38-48. [DOI: 10.1016/j.enzmictec.2017.01.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2016] [Revised: 12/27/2016] [Accepted: 01/11/2017] [Indexed: 10/20/2022]
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41
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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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42
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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: 11] [Impact Index Per Article: 1.4] [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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43
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Fellner M, Siakkou E, Faponle AS, Tchesnokov EP, de Visser SP, Wilbanks SM, Jameson GNL. Influence of cysteine 164 on active site structure in rat cysteine dioxygenase. J Biol Inorg Chem 2016; 21:501-10. [PMID: 27193596 DOI: 10.1007/s00775-016-1360-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Accepted: 05/07/2016] [Indexed: 11/29/2022]
Abstract
Cysteine dioxygenase is a non-heme mononuclear iron enzyme with unique structural features, namely an intramolecular thioether cross-link between cysteine 93 and tyrosine 157, and a disulfide bond between substrate L-cysteine and cysteine 164 in the entrance channel to the active site. We investigated how these posttranslational modifications affect catalysis through a kinetic, crystallographic and computational study. The enzyme kinetics of a C164S variant are identical to WT, indicating that disulfide formation at C164 does not significantly impair access to the active site at physiological pH. However, at high pH, the cysteine-tyrosine cross-link formation is enhanced in C164S. This supports the view that disulfide formation at position 164 can limit access to the active site. The C164S variant yielded crystal structures of unusual clarity in both resting state and with cysteine bound. Both show that the iron in the cysteine-bound complex is a mixture of penta- and hexa-coordinate with a water molecule taking up the final site (60 % occupancy), which is where dioxygen is believed to coordinate during turnover. The serine also displays stronger hydrogen bond interactions to a water bound to the amine of the substrate cysteine. However, the interactions between cysteine and iron appear unchanged. DFT calculations support this and show that WT and C164S have similar binding energies for the water molecule in the final site. This variant therefore provides evidence that WT also exists in an equilibrium between penta- and hexa-coordinate forms and the presence of the sixth ligand does not strongly affect dioxygen binding.
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Affiliation(s)
- Matthias Fellner
- Department of Chemistry, University of Otago, PO Box 56, Dunedin, 9054, New Zealand
| | - Eleni Siakkou
- Department of Chemistry, University of Otago, PO Box 56, Dunedin, 9054, New Zealand
| | - Abayomi S Faponle
- Manchester Institute of Biotechnology and School of Chemical Engineering and Analytical Science, The University of Manchester, 131 Princess Street, Manchester, M1 7DN, UK
| | - Egor P Tchesnokov
- Department of Chemistry, University of Otago, PO Box 56, Dunedin, 9054, New Zealand
| | - Sam P de Visser
- Manchester Institute of Biotechnology and School of Chemical Engineering and Analytical Science, The University of Manchester, 131 Princess Street, Manchester, M1 7DN, UK
| | - Sigurd M Wilbanks
- Department of Biochemistry, University of Otago, PO Box 56, Dunedin, 9054, New Zealand
| | - Guy N L Jameson
- Department of Chemistry, University of Otago, PO Box 56, Dunedin, 9054, New Zealand.
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44
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Fellner M, Aloi S, Tchesnokov EP, Wilbanks SM, Jameson GNL. Substrate and pH-Dependent Kinetic Profile of 3-Mercaptopropionate Dioxygenase from Pseudomonas aeruginosa. Biochemistry 2016; 55:1362-71. [DOI: 10.1021/acs.biochem.5b01203] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Matthias Fellner
- Department of Chemistry and ‡Department of
Biochemistry, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand
| | - Sekotilani Aloi
- Department of Chemistry and ‡Department of
Biochemistry, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand
| | - Egor P. Tchesnokov
- Department of Chemistry and ‡Department of
Biochemistry, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand
| | - Sigurd M. Wilbanks
- Department of Chemistry and ‡Department of
Biochemistry, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand
| | - Guy N. L. Jameson
- Department of Chemistry and ‡Department of
Biochemistry, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand
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45
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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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46
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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: 27] [Impact Index Per Article: 3.0] [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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47
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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: 45] [Impact Index Per Article: 5.0] [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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48
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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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49
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Tevatia R, Allen J, Rudrappa D, White D, Clemente TE, Cerutti H, Demirel Y, Blum P. The taurine biosynthetic pathway of microalgae. ALGAL RES 2015. [DOI: 10.1016/j.algal.2015.02.012] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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50
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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: 24] [Impact Index Per Article: 2.7] [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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