1
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Szaleniec M, Oleksy G, Sekuła A, Aleksić I, Pietras R, Sarewicz M, Krämer K, Pierik AJ, Heider J. Modeling the Initiation Phase of the Catalytic Cycle in the Glycyl-Radical Enzyme Benzylsuccinate Synthase. J Phys Chem B 2024. [PMID: 38848492 DOI: 10.1021/acs.jpcb.4c01237] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2024]
Abstract
The reaction of benzylsuccinate synthase, the radical-based addition of toluene to a fumarate cosubstrate, is initiated by hydrogen transfer from a conserved cysteine to the nearby glycyl radical in the active center of the enzyme. In this study, we analyze this step by comprehensive computer modeling, predicting (i) the influence of bound substrates or products, (ii) the energy profiles of forward- and backward hydrogen-transfer reactions, (iii) their kinetic constants and potential mechanisms, (iv) enantiospecificity differences, and (v) kinetic isotope effects. Moreover, we support several of the computational predictions experimentally, providing evidence for the predicted H/D-exchange reactions into the product and at the glycyl radical site. Our data indicate that the hydrogen transfer reactions between the active site glycyl and cysteine are principally reversible, but their rates differ strongly depending on their stereochemical orientation, transfer of protium or deuterium, and the presence or absence of substrates or products in the active site. This is particularly evident for the isotope exchange of the remaining protium atom of the glycyl radical to deuterium, which appears dependent on substrate or product binding, explaining why the exchange is observed in some, but not all, glycyl-radical enzymes.
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Affiliation(s)
- Maciej Szaleniec
- Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, Kraków 31-201, Poland
| | - Gabriela Oleksy
- Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, Kraków 31-201, Poland
- Department of Biology, Laboratory for Microbial Biochemistry, Philipps University Marburg, Marburg 35043, Germany
| | - Anna Sekuła
- Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, Kraków 31-201, Poland
| | - Ivana Aleksić
- Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, Kraków 31-201, Poland
| | - Rafał Pietras
- Department of Molecular Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Kraków 31-007, Poland
| | - Marcin Sarewicz
- Department of Molecular Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Kraków 31-007, Poland
| | - Kai Krämer
- Department of Biology, Laboratory for Microbial Biochemistry, Philipps University Marburg, Marburg 35043, Germany
| | - Antonio J Pierik
- Biochemistry, Faculty of ChemistryRPTU Kaiserslautern-Landau, Kaiserslautern D-67663, Germany
| | - Johann Heider
- Department of Biology, Laboratory for Microbial Biochemistry, Philipps University Marburg, Marburg 35043, Germany
- Synmikro-Center for Synthetic Microbiology, Philipps University Marburg, Marburg 35043, Germany
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2
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Deng WH, Liao RZ. Cysteine Radical and Glutamate Collaboratively Enable C-H Bond Activation and C-N Bond Cleavage in a Glycyl Radical Enzyme HplG. J Chem Inf Model 2024; 64:4168-4179. [PMID: 38745447 DOI: 10.1021/acs.jcim.4c00122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/16/2024]
Abstract
Hydroxyprolines are abundant in nature and widely utilized by many living organisms. Isomerization of trans-4-hydroxy-d-proline (t4D-HP) to generate 2-amino-4-ketopentanoate has been found to need a glycyl radical enzyme HplG, which catalyzes the cleavage of the C-N bond, while dehydration of trans-4-hydroxy-l-proline involves a homologous enzyme of HplG. Herein, molecular dynamics simulations and quantum mechanics/molecular mechanics (QM/MM) calculations are employed to understand the reaction mechanism of HplG. Two possible reaction pathways of HplG have been explored to decipher the origin of its chemoselectivity. The QM/MM calculations reveal that the isomerization proceeds via an initial hydrogen shift from the Cγ site of t4D-HP to a catalytic cysteine radical, followed by cleavage of the Cδ-N bond in t4D-HP to form a radical intermediate that captures a hydrogen atom from the cysteine. Activation of the Cδ-H bond in t4D-HP to bring about dehydration of t4D-HP possesses an extremely high energy barrier, thus rendering the dehydration pathway implausible in HplG. On the basis of the current calculations, conserved residue Glu429 plays a pivotal role in the isomerization pathway: the hydrogen bonding between it and t4D-HP weakens the hydroxyalkyl Cγ-Hγ bond, and it acts as a proton acceptor to trigger the cleavage of the C-N bond in t4D-HP. Our current QM/MM calculations rationalize the origin of the experimentally observed chemoselectivity of HplG and propose an H-bond-assisted bond activation strategy in radical-containing enzymes. These findings have general implications on radical-mediated enzymatic catalysis and expand our understanding of how nature wisely and selectively activates the C-H bond to modulate catalytic selectivity.
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Affiliation(s)
- Wen-Hao Deng
- Key Laboratory of Material Chemistry for Energy Conversion and Storage, Ministry of Education, Hubei Key Laboratory of Bioinorganic Chemistry and Materia Medica, Hubei Key Laboratory of Materials Chemistry and Service Failure, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Rong-Zhen Liao
- Key Laboratory of Material Chemistry for Energy Conversion and Storage, Ministry of Education, Hubei Key Laboratory of Bioinorganic Chemistry and Materia Medica, Hubei Key Laboratory of Materials Chemistry and Service Failure, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
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3
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Song DY, Stubbe J, Nocera DG. Protein engineering a PhotoRNR chimera based on a unifying evolutionary apparatus among the natural classes of ribonucleotide reductases. Proc Natl Acad Sci U S A 2024; 121:e2317291121. [PMID: 38648489 PMCID: PMC11067019 DOI: 10.1073/pnas.2317291121] [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: 10/05/2023] [Accepted: 03/19/2024] [Indexed: 04/25/2024] Open
Abstract
Ribonucleotide reductases (RNRs) are essential enzymes that catalyze the de novo transformation of nucleoside 5'-di(tri)phosphates [ND(T)Ps, where N is A, U, C, or G] to their corresponding deoxynucleotides. Despite the diversity of factors required for function and the low sequence conservation across RNRs, a unifying apparatus consolidating RNR activity is explored. We combine aspects of the protein subunit simplicity of class II RNR with a modified version of Escherichia coli class la photoRNRs that initiate radical chemistry with light to engineer a mimic of a class II enzyme. The design of this RNR involves fusing a truncated form of the active site containing α subunit with the functionally important C-terminal tail of the radical-generating β subunit to render a chimeric RNR. Inspired by a recent cryo-EM structure, a [Re] photooxidant is located adjacent to Y356[β], which is an essential component of the radical transport pathway in class I RNRs. Combination of this RNR photochimera with cytidine diphosphate (CDP), adenosine triphosphate (ATP), and light resulted in the generation of Y356• along with production of deoxycytidine diphosphate (dCDP) and cytosine. The photoproducts reflect an active site chemistry consistent with both the consensus mechanism of RNR and chemistry observed when RNR is inactivated by mechanism-based inhibitors in the active site. The enzymatic activity of the RNR photochimera in the absence of any β metallocofactor highlights the adaptability of the 10-stranded αβ barrel finger loop to support deoxynucleotide formation and accommodate the design of engineered RNRs.
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Affiliation(s)
- David Y. Song
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA02138
| | - JoAnne Stubbe
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA02138
| | - Daniel G. Nocera
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA02138
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4
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Kammel M, Erdmann C, Sawers RG. The formate-hydrogen axis and its impact on the physiology of enterobacterial fermentation. Adv Microb Physiol 2024; 84:51-82. [PMID: 38821634 DOI: 10.1016/bs.ampbs.2024.02.002] [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] [Indexed: 06/02/2024]
Abstract
Formic acid (HCOOH) and dihydrogen (H2) are characteristic products of enterobacterial mixed-acid fermentation, with H2 generation increasing in conjunction with a decrease in extracellular pH. Formate and acetyl-CoA are generated by radical-based and coenzyme A-dependent cleavage of pyruvate catalysed by pyruvate formate-lyase (PflB). Formate is also the source of H2, which is generated along with carbon dioxide through the action of the membrane-associated, cytoplasmically-oriented formate hydrogenlyase (FHL-1) complex. Synthesis of the FHL-1 complex is completely dependent on the cytoplasmic accumulation of formate. Consequently, formate determines its own disproportionation into H2 and CO2 by the FHL-1 complex. Cytoplasmic formate levels are controlled by FocA, a pentameric channel that translocates formic acid/formate bidirectionally between the cytoplasm and periplasm. Each protomer of FocA has a narrow hydrophobic pore through which neutral formic acid can pass. Two conserved amino acid residues, a histidine and a threonine, at the center of the pore control directionality of translocation. The histidine residue is essential for pH-dependent influx of formic acid. Studies with the formate analogue hypophosphite and amino acid variants of FocA suggest that the mechanisms of formic acid efflux and influx differ. Indeed, current data suggest, depending on extracellular formate levels, two separate uptake mechanisms exist, both likely contributing to maintain pH homeostasis. Bidirectional formate/formic acid translocation is dependent on PflB and influx requires an active FHL-1 complex. This review describes the coupling of formate and H2 production in enterobacteria.
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Affiliation(s)
- Michelle Kammel
- Institute of Microbiology, Martin Luther University Halle-Wittenberg, Halle, Saale, Germany
| | - Christopher Erdmann
- Institute of Microbiology, Martin Luther University Halle-Wittenberg, Halle, Saale, Germany
| | - R Gary Sawers
- Institute of Microbiology, Martin Luther University Halle-Wittenberg, Halle, Saale, Germany.
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5
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Walls WG, Vagstad AL, Delridge T, Piel J, Broderick WE, Broderick JB. Direct Detection of the α-Carbon Radical Intermediate Formed by OspD: Mechanistic Insights into Radical S-Adenosyl-l-methionine Peptide Epimerization. J Am Chem Soc 2024; 146:5550-5559. [PMID: 38364824 DOI: 10.1021/jacs.3c13829] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/18/2024]
Abstract
OspD is a radical S-adenosyl-l-methionine (SAM) peptide epimerase that converts an isoleucine (Ile) and valine (Val) of the OspA substrate to d-amino acids during biosynthesis of the ribosomally synthesized and post-translationally modified peptide (RiPP) natural product landornamide A. OspD is proposed to carry out this reaction via α-carbon (Cα) H-atom abstraction to form a peptidyl Cα radical that is stereospecifically quenched by hydrogen atom transfer (HAT) from a conserved cysteine (Cys). Here we use site-directed mutagenesis, freeze-quench trapping, isotopic labeling, and electron paramagnetic resonance (EPR) spectroscopy to provide new insights into the OspD catalytic mechanism including the direct observation of the substrate peptide Cα radical intermediate. The putative quenching Cys334 was changed to serine to generate an OspD C334S variant impaired in HAT quenching. The reaction of reduced OspD C334S with SAM and OspA freeze-quenched at 15 s exhibits a doublet EPR signal characteristic of a Cα radical coupled to a single β-H. Using isotopologues of OspA deuterated at either Ile or Val, or both Ile and Val, reveals that the initial Cα radical intermediate forms exclusively on the Ile of OspA. Time-dependent freeze quench coupled with EPR spectroscopy provided evidence for loss of the Ile Cα radical concomitant with gain of a Val Cα radical, directly demonstrating the N-to-C directionality of epimerization by OspD. These results provide direct evidence for the aforementioned OspD-catalyzed peptide epimerization mechanism via a central Cα radical intermediate during RiPP maturation of OspA, a mechanism that may extend to other proteusin peptide epimerases.
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Affiliation(s)
- William G Walls
- Department of Chemistry & Biochemistry, Montana State University, Bozeman, Montana 59717, United States
| | - Anna L Vagstad
- Institute of Microbiology, Eidgenössische Technische Hochschule (ETH) Zürich, Vladimir-Prelog-Weg 4, Zürich 8093, Switzerland
| | - Tyler Delridge
- Department of Chemistry & Biochemistry, Montana State University, Bozeman, Montana 59717, United States
| | - Jörn Piel
- Institute of Microbiology, Eidgenössische Technische Hochschule (ETH) Zürich, Vladimir-Prelog-Weg 4, Zürich 8093, Switzerland
| | - William E Broderick
- Department of Chemistry & Biochemistry, Montana State University, Bozeman, Montana 59717, United States
| | - Joan B Broderick
- Department of Chemistry & Biochemistry, Montana State University, Bozeman, Montana 59717, United States
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6
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Cáceres JC, Dolmatch A, Greene BL. The Mechanism of Inhibition of Pyruvate Formate Lyase by Methacrylate. J Am Chem Soc 2023; 145:22504-22515. [PMID: 37797332 PMCID: PMC10591478 DOI: 10.1021/jacs.3c07256] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2023] [Indexed: 10/07/2023]
Abstract
Pyruvate Formate Lyase (PFL) catalyzes acetyl transfer from pyruvate to coenzyme a by a mechanism involving multiple amino acid radicals. A post-translationally installed glycyl radical (G734· in Escherichia coli) is essential for enzyme activity and two cysteines (C418 and C419) are proposed to form thiyl radicals during turnover, yet their unique roles in catalysis have not been directly demonstrated with both structural and electronic resolution. Methacrylate is an isostructural analog of pyruvate and an informative irreversible inhibitor of pfl. Here we demonstrate the mechanism of inhibition of pfl by methacrylate. Treatment of activated pfl with methacrylate results in the conversion of the G734· to a new radical species, concomitant with enzyme inhibition, centered at g = 2.0033. Spectral simulations, reactions with methacrylate isotopologues, and Density Functional Theory (DFT) calculations support our assignment of the radical to a C2 tertiary methacryl radical. The reaction is specific for C418, as evidenced by mass spectrometry. The methacryl radical decays over time, reforming G734·, and the decay exhibits a H/D solvent isotope effect of 3.4, consistent with H-atom transfer from an ionizable donor, presumably the C419 sulfhydryl group. Acrylate also inhibits PFL irreversibly, and alkylates C418, but we did not observe an acryl secondary radical in H2O or in D2O within 10 s, consistent with our DFT calculations and the expected reactivity of a secondary versus tertiary carbon-centered radical. Together, the results support unique roles of the two active site cysteines of PFL and a C419 S-H bond dissociation energy between that of a secondary and tertiary C-H bond.
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Affiliation(s)
- Juan Carlos Cáceres
- Biomolecular
Science and Engineering Program, University
of California, Santa
Barbara, California 93106, United States
| | - August Dolmatch
- Department
of Chemistry and Biochemistry, University
of California, Santa Barbara, California 93106, United States
| | - Brandon L. Greene
- Biomolecular
Science and Engineering Program, University
of California, Santa
Barbara, California 93106, United States
- Department
of Chemistry and Biochemistry, University
of California, Santa Barbara, California 93106, United States
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7
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Andorfer MC, King-Roberts DT, Imrich CN, Brotheridge BG, Drennan CL. Development of an in vitro method for activation of X-succinate synthases for fumarate hydroalkylation. iScience 2023; 26:106902. [PMID: 37283811 PMCID: PMC10239695 DOI: 10.1016/j.isci.2023.106902] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Revised: 05/08/2023] [Accepted: 05/12/2023] [Indexed: 06/08/2023] Open
Abstract
Anaerobic microbial degradation of hydrocarbons is often initiated through addition of the hydrocarbon to fumarate by enzymes known as X-succinate synthases (XSSs). XSSs use a glycyl radical cofactor, which is installed by an activating enzyme (XSS-AE), to catalyze this carbon-carbon coupling reaction. The activation step, although crucial for catalysis, has not previously been possible in vitro because of insolubility of XSS-AEs. Here, we take a genome mining approach to find an XSS-AE, a 4-isopropylbenzylsuccinate synthase (IBSS)-AE (IbsAE) that can be solubly expressed in Escherichia coli. This soluble XSS-AE can activate both IBSS and the well-studied benzylsuccinate synthase (BSS) in vitro, allowing us to explore XSSs biochemically. To start, we examine the role of BSS subunits and find that the beta subunit accelerates the rate of hydrocarbon addition. Looking forward, the methodology and insight gathered here can be used more broadly to understand and engineer XSSs as synthetically useful biocatalysts.
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Affiliation(s)
- Mary C. Andorfer
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Devin T. King-Roberts
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Christa N. Imrich
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Balyn G. Brotheridge
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Catherine L. Drennan
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
- Center for Environmental Health, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
- Bio-inspired Solar Energy Program, Canadian Institute for Advanced Research (CIFAR), Toronto, ON M5G 1M1, Canada
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8
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Yuan F, Su B, Yu Y, Wang J. Study and design of amino acid-based radical enzymes using unnatural amino acids. RSC Chem Biol 2023; 4:431-446. [PMID: 37292061 PMCID: PMC10246556 DOI: 10.1039/d2cb00250g] [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: 12/17/2022] [Accepted: 05/17/2023] [Indexed: 06/10/2023] Open
Abstract
Radical enzymes harness the power of reactive radical species by placing them in a protein scaffold, and they are capable of catalysing many important reactions. New native radical enzymes, especially those with amino acid-based radicals, in the category of non-heme iron enzymes (including ribonucleotide reductases), heme enzymes, copper enzymes, and FAD-radical enzymes have been discovered and characterized. We discussed recent research efforts to discover new native amino acid-based radical enzymes, and to study the roles of radicals in processes such as enzyme catalysis and electron transfer. Furthermore, design of radical enzymes in a small and simple scaffold not only allows us to study the radical in a well-controlled system and test our understanding of the native enzymes, but also allows us to create powerful enzymes. In the study and design of amino acid-based radical enzymes, the use of unnatural amino acids allows precise control of pKa values and reduction potentials of the residue, as well as probing the location of the radical through spectroscopic methods, making it a powerful research tool. Our understanding of amino acid-based radical enzymes will allow us to tailor them to create powerful catalysts and better therapeutics.
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Affiliation(s)
- Feiyan Yuan
- Institute of Biochemical Engineering, Key Laboratory of Medical Molecule Science and Pharmaceutical Engineering, Ministry of Industry and Information Technology, School of Chemistry and Chemical Engineering, Beijing Institute of Technology Beijing 102488 China
| | - Binbin Su
- Institute of Biochemical Engineering, Key Laboratory of Medical Molecule Science and Pharmaceutical Engineering, Ministry of Industry and Information Technology, School of Chemistry and Chemical Engineering, Beijing Institute of Technology Beijing 102488 China
| | - Yang Yu
- Institute of Biochemical Engineering, Key Laboratory of Medical Molecule Science and Pharmaceutical Engineering, Ministry of Industry and Information Technology, School of Chemistry and Chemical Engineering, Beijing Institute of Technology Beijing 102488 China
| | - Jiangyun Wang
- Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences Beijing 100101 China
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9
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EFI-EST, EFI-GNT, and EFI-CGFP: Enzyme Function Initiative (EFI) Web Resource for Genomic Enzymology Tools. J Mol Biol 2023. [DOI: 10.1016/j.jmb.2023.168018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
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10
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Peltier JL, Serrato MR, Thery V, Pecaut J, Tomás-Mendivil E, Bertrand G, Jazzar R, Martin D. An air-stable radical with a redox-chameleonic amide. Chem Commun (Camb) 2023; 59:595-598. [PMID: 36524847 DOI: 10.1039/d2cc05404c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
An air-stable (amino)(amido)radical was synthesized by reacting a cyclic (alkyl)(amino)carbene with carbazoyl chloride, followed by one-electron reduction. We show that an adjacent radical center weakens the amide bond. It enables the amino group to act as a strong acceptor under steric contraint, thus enhancing the stabilizing capto-dative effect.
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Affiliation(s)
- Jesse L Peltier
- UCSD-CNRS Joint Research Chemistry Laboratory (IRL 3555), Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California 92093-0358, USA
| | - Melinda R Serrato
- UCSD-CNRS Joint Research Chemistry Laboratory (IRL 3555), Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California 92093-0358, USA
| | - Valentin Thery
- University Grenoble Alpes, CNRS, DCM, Grenoble 38000, France.
| | - Jacques Pecaut
- University Grenoble Alpes, CEA, CNRS, INAC-SyMMES, UMR 5819, Grenoble 38000, France
| | | | - Guy Bertrand
- UCSD-CNRS Joint Research Chemistry Laboratory (IRL 3555), Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California 92093-0358, USA
| | - Rodolphe Jazzar
- UCSD-CNRS Joint Research Chemistry Laboratory (IRL 3555), Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California 92093-0358, USA
| | - David Martin
- University Grenoble Alpes, CNRS, DCM, Grenoble 38000, France.
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11
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Kammel M, Pinske C, Sawers RG. FocA and its central role in fine-tuning pH homeostasis of enterobacterial formate metabolism. MICROBIOLOGY (READING, ENGLAND) 2022; 168. [PMID: 36197793 DOI: 10.1099/mic.0.001253] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
During enterobacterial mixed-acid fermentation, formate is generated from pyruvate by the glycyl-radical enzyme pyruvate formate-lyase (PflB). In Escherichia coli, especially at low pH, formate is then disproportionated to CO2 and H2 by the cytoplasmically oriented, membrane-associated formate hydrogenlyase (FHL) complex. If electron acceptors are available, however, formate is oxidized by periplasmically oriented, respiratory formate dehydrogenases. Formate translocation across the cytoplasmic membrane is controlled by the formate channel, FocA, a member of the formate-nitrite transporter (FNT) family of homopentameric anion channels. This review highlights recent advances in our understanding of how FocA helps to maintain intracellular formate and pH homeostasis during fermentation. Efflux and influx of formate/formic acid are distinct processes performed by FocA and both are controlled through protein interaction between FocA's N-terminal domain with PflB. Formic acid efflux by FocA helps to maintain cytoplasmic pH balance during exponential-phase growth. Uptake of formate against the electrochemical gradient (inside negative) is energetically and mechanistically challenging for a fermenting bacterium unless coupled with proton/cation symport. Translocation of formate/formic acid into the cytoplasm necessitates an active FHL complex, whose synthesis also depends on formate. Thus, FocA, FHL and PflB function together to govern formate homeostasis. We explain how FocA achieves efflux of formic acid and propose mechanisms for pH-dependent uptake of formate both with and without proton symport. We propose that FocA displays both channel- and transporter-like behaviour. Whether this translocation behaviour is shared by other members of the FNT family is also discussed.
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Affiliation(s)
- Michelle Kammel
- Institute of Microbiology, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
| | - Constanze Pinske
- Institute of Microbiology, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
| | - R Gary Sawers
- Institute of Microbiology, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
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12
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Jäger C, Croft AK. If It Is Hard, It Is Worth Doing: Engineering Radical Enzymes from Anaerobes. Biochemistry 2022; 62:241-252. [PMID: 36121716 PMCID: PMC9850924 DOI: 10.1021/acs.biochem.2c00376] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
With a pressing need for sustainable chemistries, radical enzymes from anaerobes offer a shortcut for many chemical transformations and deliver highly sought-after functionalizations such as late-stage C-H functionalization, C-C bond formation, and carbon-skeleton rearrangements, among others. The challenges in handling these oxygen-sensitive enzymes are reflected in their limited industrial exploitation, despite what they may deliver. With an influx of structures and mechanistic understanding, the scope for designed radical enzymes to deliver wanted processes becomes ever closer. Combined with new advances in computational methods and workflows for these complex systems, the outlook for an increased use of radical enzymes in future processes is exciting.
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13
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Michodigni NF, Nyachieo A, Akhwale JK, Magoma G, Kimang'a AN. Genomic evaluation of novel Kenyan virulent phage isolates infecting carbapenemase-producing Klebsiella pneumoniae and safety determination of their lysates in Balb/c mice. Arch Microbiol 2022; 204:532. [PMID: 35904691 DOI: 10.1007/s00203-022-03143-x] [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: 04/12/2022] [Revised: 07/11/2022] [Accepted: 07/14/2022] [Indexed: 11/02/2022]
Abstract
This study aimed to evaluate the genomic features of novel Kenyan virulent phage isolates infecting carbapenemase-producing Klebsiella pneumoniae and to determine the safety of their lysates using mice model in a preclinical study. The genomics showed that the Klebsiella phages vB_KpM_CPRSA and vB_KpM_CPRSB belonged to the genus Slopekvirus with a similarity index of less than 92% compared to the most closest relative species. Their genomes did not contain antimicrobial resistance and toxin genes. Then endotoxin levels in the Klebsiella phage lysates were statistically significant (p value ˃ 0.05). The serum activities of aspartate aminotransferase, alanine aminotransferase and urea in the group of balb/c mice injected with bacteriophage lysates through the intravenous route were higher compared to that of the intranasal route. Unexpectedly, there was mild congestion of the central veins of kidneys and liver without damage to renal tubules and hepatocytes and a lack of physical discomfort and pain in the mice. Our study isolated and characterised Klebsiella phages against carbapenem-resistant K. pneumoniae, which are promising therapeutic agents for the treatment of respiratory tract infections using the topical mode of administration as the preferred route of bacteriophage delivery.
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Affiliation(s)
- Noutin Fernand Michodigni
- Department of Molecular Biology and Biotechnology, Pan African University Institute for Basic Sciences Technology and Innovation (PAUSTI), Nairobi, Kenya.
- Department of Reproductive Health and Biology, Phage Biology Laboratory, Institute of Primate Research (IPR), Nairobi, Kenya.
| | - Atunga Nyachieo
- Department of Reproductive Health and Biology, Phage Biology Laboratory, Institute of Primate Research (IPR), Nairobi, Kenya
| | - Juliah Khayeli Akhwale
- Department of Zoology, School of Biological Sciences, Jomo Kenyatta University of Agriculture and Technology (JKUAT), Nairobi, Kenya
| | - Gabriel Magoma
- Department of Molecular Biology and Biotechnology, Pan African University Institute for Basic Sciences Technology and Innovation (PAUSTI), Nairobi, Kenya
- Department of Biochemistry, College of Health Sciences, Jomo Kenyatta University of Agriculture and Technology (JKUAT), Nairobi, Kenya
| | - Andrew Nyerere Kimang'a
- Department of Medical Microbiology, College of Health Sciences, Jomo Kenyatta University of Agriculture and Technology (JKUAT), Nairobi, Kenya
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14
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Hanževački M, Croft AK, Jäger CM. Activation of Glycyl Radical Enzymes─Multiscale Modeling Insights into Catalysis and Radical Control in a Pyruvate Formate-Lyase-Activating Enzyme. J Chem Inf Model 2022; 62:3401-3414. [PMID: 35771966 PMCID: PMC9326890 DOI: 10.1021/acs.jcim.2c00362] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Pyruvate formate-lyase (PFL) is a glycyl radical enzyme (GRE) playing a pivotal role in the metabolism of strict and facultative anaerobes. Its activation is carried out by a PFL-activating enzyme, a member of the radical S-adenosylmethionine (rSAM) superfamily of metalloenzymes, which introduces a glycyl radical into the Gly radical domain of PFL. The activation mechanism is still not fully understood and is structurally based on a complex with a short model peptide of PFL. Here, we present extensive molecular dynamics simulations in combination with quantum mechanics/molecular mechanics (QM/MM)-based kinetic and thermodynamic reaction evaluations of a more complete activation model comprising the 49 amino acid long C-terminus region of PFL. We reveal the benefits and pitfalls of the current activation model, providing evidence that the bound peptide conformation does not resemble the bound protein-protein complex conformation with PFL, with implications for the activation process. Substitution of the central glycine with (S)- and (R)-alanine showed excellent binding of (R)-alanine over unstable binding of (S)-alanine. Radical stabilization calculations indicate that a higher radical stability of the glycyl radical might not be the sole origin of the evolutionary development of GREs. QM/MM-derived radical formation kinetics further demonstrate feasible activation barriers for both peptide and C-terminus activation, demonstrating why the crystalized model peptide system is an excellent inhibitory system for natural activation. This new evidence supports the theory that GREs converged on glycyl radical formation due to the better conformational accessibility of the glycine radical loop, rather than the highest radical stability of the formed peptide radicals.
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Affiliation(s)
- Marko Hanževački
- Department of Chemical and Environmental Engineering, University of Nottingham, Nottingham NG7 2RD, U.K
| | - Anna K Croft
- Department of Chemical and Environmental Engineering, University of Nottingham, Nottingham NG7 2RD, U.K
| | - Christof M Jäger
- Department of Chemical and Environmental Engineering, University of Nottingham, Nottingham NG7 2RD, U.K
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15
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Fu B, Nazemi A, Levin BJ, Yang Z, Kulik HJ, Balskus EP. Mechanistic Studies of a Skatole-Forming Glycyl Radical Enzyme Suggest Reaction Initiation via Hydrogen Atom Transfer. J Am Chem Soc 2022; 144:11110-11119. [PMID: 35704859 PMCID: PMC9248008 DOI: 10.1021/jacs.1c13580] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
Gut microbial decarboxylation
of amino acid-derived arylacetates
is a chemically challenging enzymatic transformation which generates
small molecules that impact host physiology. The glycyl radical enzyme
(GRE) indoleacetate decarboxylase from Olsenella uli (Ou IAD) performs the non-oxidative radical decarboxylation
of indole-3-acetate (I3A) to yield skatole, a disease-associated metabolite
produced in the guts of swine and ruminants. Despite the importance
of IAD, our understanding of its mechanism is limited. Here, we characterize
the mechanism of Ou IAD, evaluating previously proposed
hypotheses of: (1) a Kolbe-type decarboxylation reaction involving
an initial 1-e– oxidation of the carboxylate of
I3A or (2) a hydrogen atom abstraction from the α-carbon of
I3A to generate an initial carbon-centered radical. Site-directed
mutagenesis, kinetic isotope effect experiments, analysis of reactions
performed in D2O, and computational modeling are consistent
with a mechanism involving initial hydrogen atom transfer. This finding
expands the types of radical mechanisms employed by GRE decarboxylases
and non-oxidative decarboxylases, more broadly. Elucidating the mechanism
of IAD decarboxylation enhances our understanding of radical enzymes
and may inform downstream efforts to modulate this disease-associated
metabolism.
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Affiliation(s)
- Beverly Fu
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, United States
| | - Azadeh Nazemi
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Benjamin J Levin
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, United States
| | - Zhongyue Yang
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Heather J Kulik
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Emily P Balskus
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, United States.,Howard Hughes Medical Institute, Harvard University, Cambridge, Massachusetts 02138, United States
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16
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Levitz TS, Andree GA, Jonnalagadda R, Dawson CD, Bjork RE, Drennan CL. A rapid and sensitive assay for quantifying the activity of both aerobic and anaerobic ribonucleotide reductases acting upon any or all substrates. PLoS One 2022; 17:e0269572. [PMID: 35675376 PMCID: PMC9176816 DOI: 10.1371/journal.pone.0269572] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Accepted: 05/23/2022] [Indexed: 01/21/2023] Open
Abstract
Ribonucleotide reductases (RNRs) use radical-based chemistry to catalyze the conversion of all four ribonucleotides to deoxyribonucleotides. The ubiquitous nature of RNRs necessitates multiple RNR classes that differ from each other in terms of the phosphorylation state of the ribonucleotide substrates, oxygen tolerance, and the nature of both the metallocofactor employed and the reducing systems. Although these differences allow RNRs to produce deoxyribonucleotides needed for DNA biosynthesis under a wide range of environmental conditions, they also present a challenge for establishment of a universal activity assay. Additionally, many current RNR assays are limited in that they only follow the conversion of one ribonucleotide substrate at a time, but in the cell, all four ribonucleotides are actively being converted into deoxyribonucleotide products as dictated by the cellular concentrations of allosteric specificity effectors. Here, we present a liquid chromatography with tandem mass spectrometry (LC-MS/MS)-based assay that can determine the activity of both aerobic and anaerobic RNRs on any combination of substrates using any combination of allosteric effectors. We demonstrate that this assay generates activity data similar to past published results with the canonical Escherichia coli aerobic class Ia RNR. We also show that this assay can be used for an anaerobic class III RNR that employs formate as the reductant, i.e. Streptococcus thermophilus RNR. We further show that this class III RNR is allosterically regulated by dATP and ATP. Lastly, we present activity data for the simultaneous reduction of all four ribonucleotide substrates by the E. coli class Ia RNR under various combinations of allosteric specificity effectors. This validated LC-MS/MS assay is higher throughput and more versatile than the historically established radioactive activity and coupled RNR activity assays as well as a number of the published HPLC-based assays. The presented assay will allow for the study of a wide range of RNR enzymes under a wide range of conditions, facilitating the study of previously uncharacterized RNRs.
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Affiliation(s)
- Talya S. Levitz
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, United States of America
| | - Gisele A. Andree
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, United States of America
| | - Rohan Jonnalagadda
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, United States of America
| | - Christopher D. Dawson
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, United States of America
| | - Rebekah E. Bjork
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA, United States of America
| | - Catherine L. Drennan
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, United States of America,Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, United States of America,Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA, United States of America,Center for Environmental Health Sciences, Massachusetts Institute of Technology, Cambridge, MA, United States of America,* E-mail:
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17
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Yan L, Liu Y. Mechanistic Insights into the Anaerobic Degradation of Globally Abundant Dihydroxypropanesulfonate Catalyzed by the DHPS-Sulfolyase (HpsG). J Chem Inf Model 2022; 62:2880-2888. [PMID: 35583151 DOI: 10.1021/acs.jcim.2c00174] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
2(S)-Dihydroxypropanesulfonate (DHPS) is the main abundant organosulfonate in the biosphere generated by the microbial degradation of the abundant organosulfur species 6-deoxy-6-sulfo-d-glucopyranose (sulfoquinovose, SQ). Massive amounts of DHPS can also be produced by the highly abundant oceanic diatoms. The quantity of degradation DHPS is so large that it has become an important part of the earth's sulfur. The recently characterized O2-sensitive glycyl radical enzyme DHPS-sulfolyase HpsG in anaerobic bacteria was found to be capable of cleaving the C-S bond of DHPS under anaerobic conditions. However, the detailed degradation mechanism is still unclear. Here, on the basis of the crystal structure of HpsG, we constructed the computational model and performed QM/MM calculations to illuminate the anaerobic degradation mechanism of DHPS. Our calculations revealed that the degradation reaction follows an unusual radical-dependent mechanism that does not require a conserved Glu464 to deprotonate the C2 hydroxyl of substrate to promote the C-S cleavage; instead, after the first hydrogen abstraction triggered by the thiyl radical (Cys462), the C-S bond in 2(S)-dihydroxypropanesulfonate can directly collapse. Thus, conserved Glu464 mainly plays a role in stabilizing the substrate and reaction intermediate by forming a hydrogen bond. After the release of the sulfonic acid group from the protein environment, the deprotonated Glu464 spontaneously accepts a proton from the C2 hydroxyl of the substrate radical. Our findings clarified an unusual C-S cleavage mechanism involved in the DHPS degradation reaction catalyzed by GREs.
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Affiliation(s)
- Lijuan Yan
- School of Chemistry and Chemical Engineering, Shandong University, Jinan, Shandong 250100, China
| | - Yongjun Liu
- School of Chemistry and Chemical Engineering, Shandong University, Jinan, Shandong 250100, China
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18
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Abstract
Some oxidoreductase enzymes use redox-active tyrosine, tryptophan, cysteine, and/or glycine residues as one-electron, high-potential redox (radical) cofactors. Amino-acid radical cofactors typically perform one of four tasks-they work in concert with a metallocofactor to carry out a multielectron redox process, serve as storage sites for oxidizing equivalents, activate the substrate molecules, or move oxidizing equivalents over long distances. It is challenging to experimentally resolve the thermodynamic and kinetic redox properties of a single-amino-acid residue. The inherently reactive and highly oxidizing properties of amino-acid radicals increase the experimental barriers further still. This review describes a family of stable and well-structured model proteins that was made specifically to study tyrosine and tryptophan oxidation-reduction. The so-called α3X model protein system was combined with very-high-potential protein film voltammetry, transient absorption spectroscopy, and theoretical methods to gain a comprehensive description of the thermodynamic and kinetic properties of protein tyrosine and tryptophan radicals.
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Affiliation(s)
- Cecilia Tommos
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas, USA;
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19
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Deng WH, Lu Y, Liao RZ. Revealing the Mechanism of Isethionate Sulfite-Lyase by QM/MM Calculations. J Chem Inf Model 2021; 61:5871-5882. [PMID: 34806370 DOI: 10.1021/acs.jcim.1c00978] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Isethionate sulfite-lyase (IseG) is a recently characterized glycyl radical enzyme (GRE) that catalyzes radical-mediated C-S bond cleavage of isethionate to produce acetaldehyde and sulfite. Herein, we use quantum mechanical/molecular mechanical (QM/MM) calculations to investigate the detailed catalytic reaction mechanism of IseG. Our calculations indicate that a previously proposed direct 1,2-elimination mechanism is disfavored. Instead, we suggest a new 1,2-migration mechanism for this enzymatic reaction: a key stepwise 1,2-SO3- radical migration occurs after the catalytically active cysteinyl radical grabs a hydrogen atom from isethionate, followed by hydrogen atom transfer from cysteine to a 1-hydroxylethane-1-sulfonate radical intermediate. Finally, the elimination of sulfite from 1-hydroxylethane-1-sulfonate to result in the final product is likely to occur outside the enzyme. Glu468 in the active site is found to help orient the substrate rather than grabbing a proton from the hydroxyl group of the substrate. Our findings help reveal the mechanisms of radical-mediated C-S bond cleavage of organosulfonates catalyzed by GREs and expand the understanding of radical-based enzymatic catalysis.
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Affiliation(s)
- Wen-Hao Deng
- Key Laboratory of Material Chemistry for Energy Conversion and Storage, Ministry of Education, Hubei Key Laboratory of Bioinorganic Chemistry and Materia Medica, Hubei Key Laboratory of Materials Chemistry and Service Failure, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan 430074, P. R. China
| | - You Lu
- Scientific Computing Department, UKRI STFC Daresbury Laboratory, Sci-Tech Daresbury, Warrington WA4 4AD, United Kingdom
| | - Rong-Zhen Liao
- Key Laboratory of Material Chemistry for Energy Conversion and Storage, Ministry of Education, Hubei Key Laboratory of Bioinorganic Chemistry and Materia Medica, Hubei Key Laboratory of Materials Chemistry and Service Failure, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan 430074, P. R. China
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20
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Burrichter AG, Dörr S, Bergmann P, Haiß S, Keller A, Fournier C, Franchini P, Isono E, Schleheck D. Bacterial microcompartments for isethionate desulfonation in the taurine-degrading human-gut bacterium Bilophila wadsworthia. BMC Microbiol 2021; 21:340. [PMID: 34903181 PMCID: PMC8667426 DOI: 10.1186/s12866-021-02386-w] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Accepted: 11/08/2021] [Indexed: 11/15/2022] Open
Abstract
Background Bilophila wadsworthia, a strictly anaerobic, sulfite-reducing bacterium and common member of the human gut microbiota, has been associated with diseases such as appendicitis and colitis. It is specialized on organosulfonate respiration for energy conservation, i.e., utilization of dietary and host-derived organosulfonates, such as taurine (2-aminoethansulfonate), as sulfite donors for sulfite respiration, producing hydrogen sulfide (H2S), an important intestinal metabolite that may have beneficial as well as detrimental effects on the colonic environment. Its taurine desulfonation pathway involves the glycyl radical enzyme (GRE) isethionate sulfite-lyase (IslAB), which cleaves isethionate (2-hydroxyethanesulfonate) into acetaldehyde and sulfite. Results We demonstrate that taurine metabolism in B. wadsworthia 3.1.6 involves bacterial microcompartments (BMCs). First, we confirmed taurine-inducible production of BMCs by proteomic, transcriptomic and ultra-thin sectioning and electron-microscopical analyses. Then, we isolated BMCs from taurine-grown cells by density-gradient ultracentrifugation and analyzed their composition by proteomics as well as by enzyme assays, which suggested that the GRE IslAB and acetaldehyde dehydrogenase are located inside of the BMCs. Finally, we are discussing the recycling of cofactors in the IslAB-BMCs and a potential shuttling of electrons across the BMC shell by a potential iron-sulfur (FeS) cluster-containing shell protein identified by sequence analysis. Conclusions We characterized a novel subclass of BMCs and broadened the spectrum of reactions known to take place enclosed in BMCs, which is of biotechnological interest. We also provided more details on the energy metabolism of the opportunistic pathobiont B. wadsworthia and on microbial H2S production in the human gut. Supplementary Information The online version contains supplementary material available at 10.1186/s12866-021-02386-w.
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Affiliation(s)
- Anna G Burrichter
- Department of Biology, University of Konstanz, Konstanz, Germany. .,Konstanz Research School Chemical Biology, University of Konstanz, Konstanz, Germany. .,Max von Pettenkofer Institute of Hygiene and Medical Microbiology, Faculty of Medicine, LMU Munich, Munich, Germany.
| | - Stefanie Dörr
- Department of Biology, University of Konstanz, Konstanz, Germany
| | - Paavo Bergmann
- Electron Microscopy Centre, Department of Biology, University of Konstanz, Konstanz, Germany
| | - Sebastian Haiß
- Department of Biology, University of Konstanz, Konstanz, Germany
| | - Anja Keller
- Department of Biology, University of Konstanz, Konstanz, Germany.,Konstanz Research School Chemical Biology, University of Konstanz, Konstanz, Germany
| | | | - Paolo Franchini
- Department of Biology, University of Konstanz, Konstanz, Germany
| | - Erika Isono
- Department of Biology, University of Konstanz, Konstanz, Germany
| | - David Schleheck
- Department of Biology, University of Konstanz, Konstanz, Germany. .,Konstanz Research School Chemical Biology, University of Konstanz, Konstanz, Germany.
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21
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Bathe U, Leong BJ, McCarty DR, Henry CS, Abraham PE, Wilson MA, Hanson AD. The Moderately (D)efficient Enzyme: Catalysis-Related Damage In Vivo and Its Repair. Biochemistry 2021; 60:3555-3565. [PMID: 34729986 DOI: 10.1021/acs.biochem.1c00613] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Enzymes have in vivo life spans. Analysis of life spans, i.e., lifetime totals of catalytic turnovers, suggests that nonsurvivable collateral chemical damage from the very reactions that enzymes catalyze is a common but underdiagnosed cause of enzyme death. Analysis also implies that many enzymes are moderately deficient in that their active-site regions are not naturally as hardened against such collateral damage as they could be, leaving room for improvement by rational design or directed evolution. Enzyme life span might also be improved by engineering systems that repair otherwise fatal active-site damage, of which a handful are known and more are inferred to exist. Unfortunately, the data needed to design and execute such improvements are lacking: there are too few measurements of in vivo life span, and existing information about the extent, nature, and mechanisms of active-site damage and repair during normal enzyme operation is too scarce, anecdotal, and speculative to act on. Fortunately, advances in proteomics, metabolomics, cheminformatics, comparative genomics, and structural biochemistry now empower a systematic, data-driven approach for identifying, predicting, and validating instances of active-site damage and its repair. These capabilities would be practically useful in enzyme redesign and improvement of in-use stability and could change our thinking about which enzymes die young in vivo, and why.
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Affiliation(s)
- Ulschan Bathe
- Horticultural Sciences Department, University of Florida, Gainesville, Florida 32611, United States
| | - Bryan J Leong
- Horticultural Sciences Department, University of Florida, Gainesville, Florida 32611, United States
| | - Donald R McCarty
- Horticultural Sciences Department, University of Florida, Gainesville, Florida 32611, United States
| | - Christopher S Henry
- Computing, Environment, and Life Sciences Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Paul E Abraham
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, United States
| | - Mark A Wilson
- Department of Biochemistry and Redox Biology Center, University of Nebraska, Lincoln, Nebraska 68588, United States
| | - Andrew D Hanson
- Horticultural Sciences Department, University of Florida, Gainesville, Florida 32611, United States
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22
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Rescuing activity of oxygen-damaged pyruvate formate-lyase by a spare part protein. J Biol Chem 2021; 297:101423. [PMID: 34801558 PMCID: PMC8683613 DOI: 10.1016/j.jbc.2021.101423] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2021] [Revised: 11/09/2021] [Accepted: 11/12/2021] [Indexed: 11/21/2022] Open
Abstract
Pyruvate formate-lyase (PFL) is a glycyl radical enzyme (GRE) that converts pyruvate and coenzyme A into acetyl-CoA and formate in a reaction that is crucial to the primary metabolism of many anaerobic bacteria. The glycyl radical cofactor, which is posttranslationally installed by a radical S-adenosyl-L-methionine (SAM) activase, is a simple and effective catalyst, but is also susceptible to oxidative damage in microaerobic environments. Such damage occurs at the glycyl radical cofactor, resulting in cleaved PFL (cPFL). Bacteria have evolved a spare part protein termed YfiD that can be used to repair cPFL. Previously, we obtained a structure of YfiD by NMR spectroscopy and found that the N-terminus of YfiD was disordered and that the C-terminus of YfiD duplicates the structure of the C-terminus of PFL, including a β-strand that is not removed by the oxygen-induced cleavage. We also showed that cPFL is highly susceptible to proteolysis, suggesting that YfiD rescue of cPFL competes with protein degradation. Here, we probe the mechanism by which YfiD can bind and restore activity to cPFL through enzymatic and spectroscopic studies. Our data show that the disordered N-terminal region of YfiD is important for YfiD glycyl radical installation but not for catalysis, and that the duplicate β-strand does not need to be cleaved from cPFL for YfiD to bind. In fact, truncation of this PFL region prevents YfiD rescue. Collectively our data suggest the molecular mechanisms by which YfiD activation is precluded both when PFL is not damaged and when it is highly damaged.
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23
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McLean JT, Benny A, Nolan MD, Swinand G, Scanlan EM. Cysteinyl radicals in chemical synthesis and in nature. Chem Soc Rev 2021; 50:10857-10894. [PMID: 34397045 DOI: 10.1039/d1cs00254f] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Nature harnesses the unique properties of cysteinyl radical intermediates for a diverse range of essential biological transformations including DNA biosynthesis and repair, metabolism, and biological photochemistry. In parallel, the synthetic accessibility and redox chemistry of cysteinyl radicals renders them versatile reactive intermediates for use in a vast array of synthetic applications such as lipidation, glycosylation and fluorescent labelling of proteins, peptide macrocyclization and stapling, desulfurisation of peptides and proteins, and development of novel therapeutics. This review provides the reader with an overview of the role of cysteinyl radical intermediates in both chemical synthesis and biological systems, with a critical focus on mechanistic details. Direct insights from biological systems, where applied to chemical synthesis, are highlighted and potential avenues from nature which are yet to be explored synthetically are presented.
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Affiliation(s)
- Joshua T McLean
- Trinity Biomedical Sciences Institute, Trinity College Dublin, The University of Dublin, 152-160 Pearse St., Dublin, D02 R590, Ireland.
| | - Alby Benny
- Trinity Biomedical Sciences Institute, Trinity College Dublin, The University of Dublin, 152-160 Pearse St., Dublin, D02 R590, Ireland.
| | - Mark D Nolan
- Trinity Biomedical Sciences Institute, Trinity College Dublin, The University of Dublin, 152-160 Pearse St., Dublin, D02 R590, Ireland.
| | - Glenna Swinand
- Trinity Biomedical Sciences Institute, Trinity College Dublin, The University of Dublin, 152-160 Pearse St., Dublin, D02 R590, Ireland.
| | - Eoin M Scanlan
- Trinity Biomedical Sciences Institute, Trinity College Dublin, The University of Dublin, 152-160 Pearse St., Dublin, D02 R590, Ireland.
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24
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Abstract
Radicals in biology, once thought to all be bad actors, are now known to play a central role in many enzymatic reactions. Of the known radical-based enzymes, ribonucleotide reductases (RNRs) are pre-eminent as they are essential in the biology of all organisms by providing the building blocks and controlling the fidelity of DNA replication and repair. Intense examination of RNRs has led to the development of new tools and a guiding framework for the study of radicals in biology, pointing the way to future frontiers in radical enzymology.
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Affiliation(s)
- JoAnne Stubbe
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 20139 USA
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 20139 USA
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138 USA
| | - Daniel G. Nocera
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138 USA
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25
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Schneiker A, Góbi S, Joshi PR, Bazsó G, Lee YP, Tarczay G. Non-energetic, Low-Temperature Formation of C α-Glycyl Radical, a Potential Interstellar Precursor of Natural Amino Acids. J Phys Chem Lett 2021; 12:6744-6751. [PMID: 34264091 DOI: 10.1021/acs.jpclett.1c01306] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The reaction of H atoms with glycine was investigated at 3.1 K in para-H2, a quantum-solid host. The reaction was followed by IR spectroscopy, with the spectral analysis aided by quantum chemical computations. Comparison of the experimental IR spectrum with computed anharmonic frequencies and intensities proved that, regardless of the reactant glycine conformation, Cα-glycyl radical is formed in an H-atom-abstraction process with great selectivity. The product of the second H-atom abstraction, iminoacetic acid, was also observed in a smaller amount. The Cα-glycyl radical is sensitive to UV light and decomposes to iminoacetic acid and H atom upon 280 nm radiation. Since the reactive radical center is located on the Cα-atom, it is suggested that natural α-amino acids can be formed from glycine via the Cα-glycyl radical by non-energetic mechanisms in the solid phase of the interstellar medium.
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Affiliation(s)
- Anita Schneiker
- MTA-ELTE Lendület Laboratory Astrochemistry Research Group, Institute of Chemistry, ELTE Eötvös Loránd University, H-1518 Budapest, Hungary
- Laboratory of Molecular Spectroscopy, Institute of Chemistry, ELTE Eötvös Loránd University, H-1518 Budapest, Hungary
| | - Sándor Góbi
- MTA-ELTE Lendület Laboratory Astrochemistry Research Group, Institute of Chemistry, ELTE Eötvös Loránd University, H-1518 Budapest, Hungary
| | - Prasad Ramesh Joshi
- Department of Applied Chemistry and Institute of Molecular Science, National Yang Ming Chiao Tung University, Hsinchu 300093, Taiwan
| | - Gábor Bazsó
- Wigner Research Centre for Physics, P. O. Box 49, H-1525 Budapest, Hungary
| | - Yuan-Pern Lee
- Department of Applied Chemistry and Institute of Molecular Science, National Yang Ming Chiao Tung University, Hsinchu 300093, Taiwan
- Center for Emergent Functional Matter Science, National Chiao Tung University, Hsinchu 300093, Taiwan
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 106319, Taiwan
| | - György Tarczay
- MTA-ELTE Lendület Laboratory Astrochemistry Research Group, Institute of Chemistry, ELTE Eötvös Loránd University, H-1518 Budapest, Hungary
- Laboratory of Molecular Spectroscopy, Institute of Chemistry, ELTE Eötvös Loránd University, H-1518 Budapest, Hungary
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26
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Discovery and mining of enzymes from the human gut microbiome. Trends Biotechnol 2021; 40:240-254. [PMID: 34304905 DOI: 10.1016/j.tibtech.2021.06.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Revised: 06/24/2021] [Accepted: 06/25/2021] [Indexed: 12/19/2022]
Abstract
Advances in technological and bioinformatics approaches have led to the generation of a plethora of human gut metagenomic datasets. Metabolomics has also provided substantial data regarding the small metabolites produced and modified by the microbiota. Comparatively, the microbial enzymes mediating the transformation of metabolites have not been intensively investigated. Here, we discuss the recent efforts and technologies used for discovering and mining enzymes from the human gut microbiota. The wealth of knowledge on metabolites, reactions, genome sequences, and structures of proteins, may drive the development of strategies for enzyme mining. Ongoing efforts to annotate gut microbiota enzymes will explain catalytic mechanisms that may guide the clinical applications of the gut microbiome for diagnostic and therapeutic purposes.
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27
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Yang Z, Kulik HJ. Protein Dynamics and Substrate Protonation States Mediate the Catalytic Action of trans-4-Hydroxy-l-Proline Dehydratase. J Phys Chem B 2021; 125:7774-7784. [PMID: 34236200 DOI: 10.1021/acs.jpcb.1c05320] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The enzyme trans-4-hydroxy-l-proline (Hyp) dehydratase (HypD) is among the most abundant glycyl radical enzymes (GREs) in the healthy human gut microbiome and is considered a promising antibiotic target for the prominent antibiotic-resistant pathogen Clostridium difficile. Although an enzymatic mechanism has been proposed, the role of the greater HypD protein environment in mediating radical reactivity is not well understood. To fill this gap in understanding, we investigate HypD across multiple time- and length-scales using electronic structure modeling and classical molecular dynamics. We observe that the Hyp substrate protonation state significantly alters both its enzyme-free reactivity and its dynamics within the enzyme active site. Accurate coupled-cluster modeling suggests the deprotonated form of Hyp to be the most reactive protonation state for C5-Hpro-S activation. In the protein environment, hydrophobic interactions modulate the positioning of the Cys434 radical to enhance the reactivity of C5-Hpro-S abstraction. Long-time dynamics reveal that changing Hyp protonation states triggers the switching of a Leu643-gated water tunnel, a functional feature that has not yet been observed for members of the GRE superfamily.
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Affiliation(s)
- Zhongyue Yang
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Heather J Kulik
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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28
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Lu Q, Wei Y, Lin L, Liu J, Duan Y, Li Y, Zhai W, Liu Y, Ang EL, Zhao H, Yuchi Z, Zhang Y. The Glycyl Radical Enzyme Arylacetate Decarboxylase from Olsenella scatoligenes. ACS Catal 2021. [DOI: 10.1021/acscatal.1c01253] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Qiang Lu
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency, Collaborative Innovation Center of Chemical Science and Engineering, School of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072, China
- Frontiers Science Center for Synthetic Biology (Ministry of Education), Tianjin University, Tianjin 300072, China
| | - Yifeng Wei
- Singapore Institute of Food and Biotechnology Innovation, Agency for Science, Technology and Research (A*STAR), Singapore 138669, Singapore
| | - Lianyun Lin
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency, Collaborative Innovation Center of Chemical Science and Engineering, School of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072, China
| | - Jiayi Liu
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency, Collaborative Innovation Center of Chemical Science and Engineering, School of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072, China
| | - Yongxu Duan
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency, Collaborative Innovation Center of Chemical Science and Engineering, School of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072, China
| | - Yaxin Li
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency, Collaborative Innovation Center of Chemical Science and Engineering, School of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072, China
| | - Weixiang Zhai
- Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnostics, School of Pharmacy, Tianjin Medical University, Tianjin 300070, China
| | - Yangping Liu
- Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnostics, School of Pharmacy, Tianjin Medical University, Tianjin 300070, China
| | - Ee Lui Ang
- Singapore Institute of Food and Biotechnology Innovation, Agency for Science, Technology and Research (A*STAR), Singapore 138669, Singapore
| | - Huimin Zhao
- Singapore Institute of Food and Biotechnology Innovation, Agency for Science, Technology and Research (A*STAR), Singapore 138669, Singapore
- Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana−Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, United States
| | - Zhiguang Yuchi
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency, Collaborative Innovation Center of Chemical Science and Engineering, School of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072, China
| | - Yan Zhang
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency, Collaborative Innovation Center of Chemical Science and Engineering, School of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072, China
- Frontiers Science Center for Synthetic Biology (Ministry of Education), Tianjin University, Tianjin 300072, China
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29
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Abstract
Sulfonates include diverse natural products and anthropogenic chemicals and are widespread in the environment. Many bacteria can degrade sulfonates and obtain sulfur, carbon, and energy for growth, playing important roles in the biogeochemical sulfur cycle. Cleavage of the inert sulfonate C-S bond involves a variety of enzymes, cofactors, and oxygen-dependent and oxygen-independent catalytic mechanisms. Sulfonate degradation by strictly anaerobic bacteria was recently found to involve C-S bond cleavage through O2-sensitive free radical chemistry, catalyzed by glycyl radical enzymes (GREs). The associated discoveries of new enzymes and metabolic pathways for sulfonate metabolism in diverse anaerobic bacteria have enriched our understanding of sulfonate chemistry in the anaerobic biosphere. An anaerobic environment of particular interest is the human gut microbiome, where sulfonate degradation by sulfate- and sulfite-reducing bacteria (SSRB) produces H2S, a process linked to certain chronic diseases and conditions.
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Affiliation(s)
- Yifeng Wei
- Singapore Institute of Food and Biotechnology Innovation, Agency for Science, Technology and Research (A*STAR), Singapore 138669
| | - Yan Zhang
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency, Collaborative Innovation Center of Chemical Science and Engineering, School of Pharmaceutical Science and Technology; and Frontiers Science Center for Synthetic Biology (Ministry of Education), Tianjin University, Tianjin 300072, China;
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30
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Yee EF, Oldemeyer S, Böhm E, Ganguly A, York DM, Kottke T, Crane BR. Peripheral Methionine Residues Impact Flavin Photoreduction and Protonation in an Engineered LOV Domain Light Sensor. Biochemistry 2021; 60:1148-1164. [PMID: 33787242 DOI: 10.1021/acs.biochem.1c00064] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Proton-coupled electron transfer reactions play critical roles in many aspects of sensory phototransduction. In the case of flavoprotein light sensors, reductive quenching of flavin excited states initiates chemical and conformational changes that ultimately transmit light signals to downstream targets. These reactions generally require neighboring aromatic residues and proton-donating side chains for rapid and coordinated electron and proton transfer to flavin. Although photoreduction of flavoproteins can produce either the anionic (ASQ) or neutral semiquinone (NSQ), the factors that favor one over the other are not well understood. Here we employ a biologically active variant of the light-oxygen-voltage (LOV) domain protein VVD devoid of the adduct-forming Cys residue (VVD-III) to probe the mechanism of flavin photoreduction and protonation. A series of isosteric and conservative residue replacements studied by rate measurements, fluorescence quantum yields, FTIR difference spectroscopy, and molecular dynamics simulations indicate that tyrosine residues facilitate charge recombination reactions that limit sustained flavin reduction, whereas methionine residues facilitate radical propagation and quenching and also gate solvent access for flavin protonation. Replacement of a single surface Met residue with Leu favors formation of the ASQ over the NSQ and desensitizes photoreduction to oxidants. In contrast, increasing site hydrophilicity by Gln substitution promotes rapid NSQ formation and weakens the influence of the redox environment. Overall, the photoreactivity of VVD-III can be understood in terms of redundant electron donors, internal hole quenching, and coupled proton transfer reactions that all depend upon protein conformation, dynamics, and solvent penetration.
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Affiliation(s)
- Estella F Yee
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States
| | - Sabine Oldemeyer
- Physical and Biophysical Chemistry, Department of Chemistry, Bielefeld University, 33615 Bielefeld, Germany
| | - Elena Böhm
- Physical and Biophysical Chemistry, Department of Chemistry, Bielefeld University, 33615 Bielefeld, Germany
| | - Abir Ganguly
- Laboratory for Biomolecular Simulation Research, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854-8076, United States.,Institute for Quantitative Biomedicine, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854-8076, United States
| | - Darrin M York
- Laboratory for Biomolecular Simulation Research, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854-8076, United States.,Institute for Quantitative Biomedicine, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854-8076, United States.,Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, United States
| | - Tilman Kottke
- Physical and Biophysical Chemistry, Department of Chemistry, Bielefeld University, 33615 Bielefeld, Germany
| | - Brian R Crane
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States
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31
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Dawson CD, Irwin SM, Backman LRF, Le C, Wang JX, Vennelakanti V, Yang Z, Kulik HJ, Drennan CL, Balskus EP. Molecular basis of C-S bond cleavage in the glycyl radical enzyme isethionate sulfite-lyase. Cell Chem Biol 2021; 28:1333-1346.e7. [PMID: 33773110 PMCID: PMC8473560 DOI: 10.1016/j.chembiol.2021.03.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Revised: 02/04/2021] [Accepted: 03/03/2021] [Indexed: 01/07/2023]
Abstract
Desulfonation of isethionate by the bacterial glycyl radical enzyme (GRE) isethionate sulfite-lyase (IslA) generates sulfite, a substrate for respiration that in turn produces the disease-associated metabolite hydrogen sulfide. Here, we present a 2.7 Å resolution X-ray structure of wild-type IslA from Bilophila wadsworthia with isethionate bound. In comparison with other GREs, alternate positioning of the active site β strands allows for distinct residue positions to contribute to substrate binding. These structural differences, combined with sequence variations, create a highly tailored active site for the binding of the negatively charged isethionate substrate. Through the kinetic analysis of 14 IslA variants and computational analyses, we probe the mechanism by which radical chemistry is used for C-S bond cleavage. This work further elucidates the structural basis of chemistry within the GRE superfamily and will inform structure-based inhibitor design of IsIA and thus of microbial hydrogen sulfide production.
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Affiliation(s)
- Christopher D Dawson
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Stephania M Irwin
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA
| | - Lindsey R F Backman
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Chip Le
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA
| | - Jennifer X Wang
- Harvard Center for Mass Spectrometry, Faculty of Arts and Sciences Division of Science, Harvard University, 52 Oxford Street, Cambridge, MA 02138, USA
| | - Vyshnavi Vennelakanti
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Zhongyue Yang
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Heather J Kulik
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
| | - Catherine L Drennan
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
| | - Emily P Balskus
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA; Broad Institute, Cambridge, MA 02139, USA.
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32
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Computing Proton-Coupled Redox Potentials of Fluorotyrosines in a Protein Environment. J Phys Chem B 2020; 125:128-136. [PMID: 33378205 DOI: 10.1021/acs.jpcb.0c09974] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The oxidation of tyrosine to form the neutral tyrosine radical via proton-coupled electron transfer is essential for a wide range of biological processes. The precise measurement of the proton-coupled redox potentials of tyrosine (Y) in complex protein environments is challenging mainly because of the highly oxidizing and reactive nature of the radical state. Herein, a computational strategy is presented for predicting proton-coupled redox potentials in a protein environment. In this strategy, both the reduced Y-OH and oxidized Y-O• forms of tyrosine are sampled with molecular dynamics using a molecular mechanical force field. For a large number of conformations, a quantum mechanical/molecular mechanical (QM/MM) electrostatic embedding scheme is used to compute the free-energy differences between the reduced and oxidized forms, including the zero-point energy and entropic contributions as well as the impact of the protein electrostatic environment. This strategy is applied to a series of fluorinated tyrosine derivatives embedded in a de novo α-helical protein denoted as α3Y. The force fields for both the reduced and oxidized forms of these noncanonical fluorinated tyrosine residues are parameterized for general use. The calculated relative proton-coupled redox potentials agree with experimentally measured values with a mean unsigned error of 24 mV. Analysis of the simulations illustrates that hydrogen-bonding interactions between tyrosine and water increase the redox potentials by ∼100-250 mV, with significant variations because of the fluctuating protein environment. This QM/MM approach enables the calculation of proton-coupled redox potentials of tyrosine and other residues such as tryptophan in a variety of protein systems.
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33
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Bollenbach M, Ortega M, Orman M, Drennan CL, Balskus EP. Discovery of a Cyclic Choline Analog That Inhibits Anaerobic Choline Metabolism by Human Gut Bacteria. ACS Med Chem Lett 2020; 11:1980-1985. [PMID: 33062182 DOI: 10.1021/acsmedchemlett.0c00005] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2020] [Accepted: 03/25/2020] [Indexed: 12/24/2022] Open
Abstract
The anaerobic conversion of choline to trimethylamine (TMA) by the human gut microbiota has been linked to multiple human diseases. The potential impact of this microbial metabolic activity on host health has inspired multiple efforts to identify small molecule inhibitors. Here, we use information about the structure and mechanism of the bacterial enzyme choline TMA-lyase (CutC) to develop a cyclic choline analog that inhibits the conversion of choline to TMA in bacterial whole cells and in a complex gut microbial community. In vitro biochemical assays and a crystal structure suggest that this analog is a competitive, mechanism-based inhibitor. This work demonstrates the utility of structure-based design to access inhibitors of radical enzymes from the human gut microbiota.
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Affiliation(s)
- Maud Bollenbach
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States
| | | | - Marina Orman
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States
| | | | - Emily P. Balskus
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States
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34
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Stewart KL, Stewart AM, Bobik TA. Prokaryotic Organelles: Bacterial Microcompartments in E. coli and Salmonella. EcoSal Plus 2020; 9:10.1128/ecosalplus.ESP-0025-2019. [PMID: 33030141 PMCID: PMC7552817 DOI: 10.1128/ecosalplus.esp-0025-2019] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Indexed: 02/07/2023]
Abstract
Bacterial microcompartments (MCPs) are proteinaceous organelles consisting of a metabolic pathway encapsulated within a selectively permeable protein shell. Hundreds of species of bacteria produce MCPs of at least nine different types, and MCP metabolism is associated with enteric pathogenesis, cancer, and heart disease. This review focuses chiefly on the four types of catabolic MCPs (metabolosomes) found in Escherichia coli and Salmonella: the propanediol utilization (pdu), ethanolamine utilization (eut), choline utilization (cut), and glycyl radical propanediol (grp) MCPs. Although the great majority of work done on catabolic MCPs has been carried out with Salmonella and E. coli, research outside the group is mentioned where necessary for a comprehensive understanding. Salient characteristics found across MCPs are discussed, including enzymatic reactions and shell composition, with particular attention paid to key differences between classes of MCPs. We also highlight relevant research on the dynamic processes of MCP assembly, protein targeting, and the mechanisms that underlie selective permeability. Lastly, we discuss emerging biotechnology applications based on MCP principles and point out challenges, unanswered questions, and future directions.
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Affiliation(s)
- Katie L. Stewart
- The Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA, USA 50011
| | - Andrew M. Stewart
- The Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA, USA 50011
| | - Thomas A. Bobik
- The Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA, USA 50011
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35
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Chow WY, Norman BP, Roberts NB, Ranganath LR, Teutloff C, Bittl R, Duer MJ, Gallagher JA, Oschkinat H. Pigmentierungschemie und radikalbasierter Kollagenabbau bei Alkaptonurie und Arthrose. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202000618] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Wing Ying Chow
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, im Forschungsverbund Berlin e.V. (FMP) Campus Berlin-Buch, Robert-Rössle-Straße 10 13125 Berlin Deutschland
| | - Brendan P. Norman
- Department of Musculoskeletal Biology Institute of Ageing & Chronic Disease William Henry Duncan Building University of Liverpool Liverpool L7 8TX Vereinigtes Königreich
| | - Norman B. Roberts
- Departments of Clinical Biochemistry and Metabolic Medicine Royal Liverpool and Broadgreen University Hospitals Trust Liverpool L7 8XP Vereinigtes Königreich
| | - Lakshminarayan R. Ranganath
- Department of Musculoskeletal Biology Institute of Ageing & Chronic Disease William Henry Duncan Building University of Liverpool Liverpool L7 8TX Vereinigtes Königreich
- Departments of Clinical Biochemistry and Metabolic Medicine Royal Liverpool and Broadgreen University Hospitals Trust Liverpool L7 8XP Vereinigtes Königreich
| | - Christian Teutloff
- Freie Universität Berlin Fachbereich Physik, Berlin Joint EPR Lab Arnimallee 14 14195 Berlin Deutschland
| | - Robert Bittl
- Freie Universität Berlin Fachbereich Physik, Berlin Joint EPR Lab Arnimallee 14 14195 Berlin Deutschland
| | - Melinda J. Duer
- Department of Chemistry University of Cambridge Lensfield Road Cambridge CB2 1EW Vereinigtes Königreich
| | - James A. Gallagher
- Department of Musculoskeletal Biology Institute of Ageing & Chronic Disease William Henry Duncan Building University of Liverpool Liverpool L7 8TX Vereinigtes Königreich
| | - Hartmut Oschkinat
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, im Forschungsverbund Berlin e.V. (FMP) Campus Berlin-Buch, Robert-Rössle-Straße 10 13125 Berlin Deutschland
- Freie Universität Berlin Fachbereich Biologie, Chemie und Pharmazie Takustraße 3 14195 Berlin Deutschland
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36
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Chow WY, Norman BP, Roberts NB, Ranganath LR, Teutloff C, Bittl R, Duer MJ, Gallagher JA, Oschkinat H. Pigmentation Chemistry and Radical-Based Collagen Degradation in Alkaptonuria and Osteoarthritic Cartilage. Angew Chem Int Ed Engl 2020; 59:11937-11942. [PMID: 32219972 PMCID: PMC7383862 DOI: 10.1002/anie.202000618] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Indexed: 12/12/2022]
Abstract
Alkaptonuria (AKU) is a rare disease characterized by high levels of homogentisic acid (HGA); patients suffer from tissue ochronosis: dark brown pigmentation, especially of joint cartilage, leading to severe early osteoarthropathy. No molecular mechanism links elevated HGA to ochronosis; the pigment's chemical identity is still not known, nor how it induces joint cartilage degradation. Here we give key insight on HGA-derived pigment composition and collagen disruption in AKU cartilage. Synthetic pigment and pigmented human cartilage tissue both showed hydroquinone-resembling NMR signals. EPR spectroscopy showed that the synthetic pigment contains radicals. Moreover, we observed intrastrand disruption of collagen triple helix in pigmented AKU human cartilage, and in cartilage from patients with osteoarthritis. We propose that collagen degradation can occur via transient glycyl radicals, the formation of which is enhanced in AKU due to the redox environment generated by pigmentation.
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Affiliation(s)
- Wing Ying Chow
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, im Forschungsverbund Berlin e.V. (FMP)Campus Berlin-Buch, Robert-Rössle-Str. 1013125BerlinGermany
| | - Brendan P. Norman
- Department of Musculoskeletal BiologyInstitute of Ageing & Chronic DiseaseWilliam Henry Duncan BuildingUniversity of LiverpoolLiverpoolL7 8TXUK
| | - Norman B. Roberts
- Departments of Clinical Biochemistry and Metabolic MedicineRoyal Liverpool and Broadgreen University Hospitals TrustLiverpoolL7 8XPUK
| | - Lakshminarayan R. Ranganath
- Department of Musculoskeletal BiologyInstitute of Ageing & Chronic DiseaseWilliam Henry Duncan BuildingUniversity of LiverpoolLiverpoolL7 8TXUK
- Departments of Clinical Biochemistry and Metabolic MedicineRoyal Liverpool and Broadgreen University Hospitals TrustLiverpoolL7 8XPUK
| | - Christian Teutloff
- Freie Universität BerlinFachbereich Physik, Berlin Joint EPR LabArnimallee 1414195BerlinGermany
| | - Robert Bittl
- Freie Universität BerlinFachbereich Physik, Berlin Joint EPR LabArnimallee 1414195BerlinGermany
| | - Melinda J. Duer
- Department of ChemistryUniversity of CambridgeLensfield RoadCambridgeCB2 1EWUK
| | - James A. Gallagher
- Department of Musculoskeletal BiologyInstitute of Ageing & Chronic DiseaseWilliam Henry Duncan BuildingUniversity of LiverpoolLiverpoolL7 8TXUK
| | - Hartmut Oschkinat
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, im Forschungsverbund Berlin e.V. (FMP)Campus Berlin-Buch, Robert-Rössle-Str. 1013125BerlinGermany
- Freie Universität BerlinFachbereich Biologie, Chemie und PharmazieTakustraße 314195BerlinGermany
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37
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Two radical-dependent mechanisms for anaerobic degradation of the globally abundant organosulfur compound dihydroxypropanesulfonate. Proc Natl Acad Sci U S A 2020; 117:15599-15608. [PMID: 32571930 DOI: 10.1073/pnas.2003434117] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
2(S)-dihydroxypropanesulfonate (DHPS) is a microbial degradation product of 6-deoxy-6-sulfo-d-glucopyranose (sulfoquinovose), a component of plant sulfolipid with an estimated annual production of 1010 tons. DHPS is also at millimolar levels in highly abundant marine phytoplankton. Its degradation and sulfur recycling by microbes, thus, play important roles in the biogeochemical sulfur cycle. However, DHPS degradative pathways in the anaerobic biosphere are not well understood. Here, we report the discovery and characterization of two O2-sensitive glycyl radical enzymes that use distinct mechanisms for DHPS degradation. DHPS-sulfolyase (HpsG) in sulfate- and sulfite-reducing bacteria catalyzes C-S cleavage to release sulfite for use as a terminal electron acceptor in respiration, producing H2S. DHPS-dehydratase (HpfG), in fermenting bacteria, catalyzes C-O cleavage to generate 3-sulfopropionaldehyde, subsequently reduced by the NADH-dependent sulfopropionaldehyde reductase (HpfD). Both enzymes are present in bacteria from diverse environments including human gut, suggesting the contribution of enzymatic radical chemistry to sulfur flux in various anaerobic niches.
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38
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Backman LRF, Huang YY, Andorfer MC, Gold B, Raines RT, Balskus EP, Drennan CL. Molecular basis for catabolism of the abundant metabolite trans-4-hydroxy-L-proline by a microbial glycyl radical enzyme. eLife 2020; 9:e51420. [PMID: 32180548 PMCID: PMC7077986 DOI: 10.7554/elife.51420] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Accepted: 02/19/2020] [Indexed: 02/04/2023] Open
Abstract
The glycyl radical enzyme (GRE) superfamily utilizes a glycyl radical cofactor to catalyze difficult chemical reactions in a variety of anaerobic microbial metabolic pathways. Recently, a GRE, trans-4-hydroxy-L-proline (Hyp) dehydratase (HypD), was discovered that catalyzes the dehydration of Hyp to (S)-Δ1-pyrroline-5-carboxylic acid (P5C). This enzyme is abundant in the human gut microbiome and also present in prominent bacterial pathogens. However, we lack an understanding of how HypD performs its unusual chemistry. Here, we have solved the crystal structure of HypD from the pathogen Clostridioides difficile with Hyp bound in the active site. Biochemical studies have led to the identification of key catalytic residues and have provided insight into the radical mechanism of Hyp dehydration.
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Affiliation(s)
- Lindsey RF Backman
- Department of Chemistry, Massachusetts Institute of TechnologyCambridgeUnited States
| | - Yolanda Y Huang
- Department of Chemistry and Chemical Biology, Harvard UniversityCambridgeUnited States
| | - Mary C Andorfer
- Department of Biology, Massachusetts Institute of TechnologyCambridgeUnited States
| | - Brian Gold
- Department of Chemistry, Massachusetts Institute of TechnologyCambridgeUnited States
| | - Ronald T Raines
- Department of Chemistry, Massachusetts Institute of TechnologyCambridgeUnited States
| | - Emily P Balskus
- Department of Chemistry and Chemical Biology, Harvard UniversityCambridgeUnited States
| | - Catherine L Drennan
- Department of Chemistry, Massachusetts Institute of TechnologyCambridgeUnited States
- Department of Biology, Massachusetts Institute of TechnologyCambridgeUnited States
- Howard Hughes Medical Institute, Massachusetts Institute of TechnologyCambridgeUnited States
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39
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Fu B, Balskus EP. Discovery of CC bond-forming and bond-breaking radical enzymes: enabling transformations for metabolic engineering. Curr Opin Biotechnol 2020; 65:94-101. [PMID: 32171888 PMCID: PMC7670169 DOI: 10.1016/j.copbio.2020.02.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2019] [Revised: 02/03/2020] [Accepted: 02/04/2020] [Indexed: 11/23/2022]
Abstract
Radical enzymes catalyze difficult C—C bond-forming and bond-breaking transformations. Radical enzymes catalyzing unprecedented reactions continue to be discovered. The products of radical enzymes are often of high value. Understanding mechanisms of radical enzymes will aid metabolic engineering efforts.
Radical enzymes catalyze some of the most chemically challenging C—C bond-forming and bond-breaking reactions. Advances in DNA sequencing have accelerated the discovery of radical enzymes from microbes, including radical S-adenosylmethionine (rSAM) enzymes, glycyl radical enzymes (GREs), and diiron enzymes. These enzymes catalyze various reactions that yield products of industrial relevance (e.g. aromatics, hydrocarbons, and natural product derivatives), making their incorporation into engineered metabolic pathways enticing. Elucidating the mechanisms of radical enzymes that cleave and construct C—C bonds will enable further enzyme discovery and engineering efforts.
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Affiliation(s)
- Beverly Fu
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford St., Cambridge, MA 02138, United States
| | - Emily P Balskus
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford St., Cambridge, MA 02138, United States.
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40
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Rodrigues AV, Tantillo DJ, Mukhopadhyay A, Keasling JD, Beller HR. Insight into the Mechanism of Phenylacetate Decarboxylase (PhdB), a Toluene-Producing Glycyl Radical Enzyme. Chembiochem 2020; 21:663-671. [PMID: 31512343 PMCID: PMC7079210 DOI: 10.1002/cbic.201900560] [Citation(s) in RCA: 12] [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: 09/10/2019] [Indexed: 01/14/2023]
Abstract
We recently reported the discovery of phenylacetate decarboxylase (PhdB), representing one of only ten glycyl-radical-enzyme reaction types known, and a promising biotechnological tool for first-time biochemical synthesis of toluene from renewable resources. Here, we used experimental and computational data to evaluate the plausibility of three candidate PhdB mechanisms, involving either attack at the phenylacetate methylene carbon or carboxyl group [via H-atom abstraction from COOH or single-electron oxidation of COO- (Kolbe-type decarboxylation)]. In vitro experimental data included assays with F-labeled phenylacetate, kinetic studies, and tests with site-directed PhdB mutants; computational data involved estimation of reaction energetics using density functional theory (DFT). The DFT results indicated that all three mechanisms are thermodynamically challenging (beyond the range of many known enzymes in terms of endergonicity or activation energy barrier), reflecting the formidable demands on PhdB for catalysis of this reaction. Evidence that PhdB was able to bind α,α-difluorophenylacetate but was unable to catalyze its decarboxylation supported the enzyme's abstraction of a methylene H atom. Diminished activity of H327A and Y691F mutants was consistent with proposed proton donor roles for His327 and Tyr691. Collectively, these and other data most strongly support PhdB attack at the methylene carbon.
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Affiliation(s)
- Andria V. Rodrigues
- Joint BioEnergy Institute (JBEI)5885 Hollis StreetEmeryvilleCA94608USA
- Biological Systems and EngineeringLawrence Berkeley National Laboratory1 Cyclotron RoadBerkeleyCA94720USA
| | - Dean J. Tantillo
- Department of ChemistryUniversity of California1 Shields AvenueDavisCA95616USA
| | - Aindrila Mukhopadhyay
- Joint BioEnergy Institute (JBEI)5885 Hollis StreetEmeryvilleCA94608USA
- Biological Systems and EngineeringLawrence Berkeley National Laboratory1 Cyclotron RoadBerkeleyCA94720USA
| | - Jay D. Keasling
- Joint BioEnergy Institute (JBEI)5885 Hollis StreetEmeryvilleCA94608USA
- Biological Systems and EngineeringLawrence Berkeley National Laboratory1 Cyclotron RoadBerkeleyCA94720USA
- Department of BioengineeringUniversity of California306 Stanley HallBerkeleyCA94720USA
- Department of Chemical and Biomolecular EngineeringUniversity of California201 Gilman HallBerkeleyCA94720USA
- Novo Nordisk Foundation Center for BiosustainabilityTechnical University of DenmarkBuilding 220, Kemitorvet2800Kgs. LyngbyDenmark
| | - Harry R. Beller
- Joint BioEnergy Institute (JBEI)5885 Hollis StreetEmeryvilleCA94608USA
- Biological Systems and EngineeringLawrence Berkeley National Laboratory1 Cyclotron RoadBerkeleyCA94720USA
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41
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Yee DA, Kakule TB, Cheng W, Chen M, Chong CTY, Hai Y, Hang LF, Hung YS, Liu N, Ohashi M, Okorafor IC, Song Y, Tang M, Zhang Z, Tang Y. Genome Mining of Alkaloidal Terpenoids from a Hybrid Terpene and Nonribosomal Peptide Biosynthetic Pathway. J Am Chem Soc 2020; 142:710-714. [PMID: 31885262 DOI: 10.1021/jacs.9b13046] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Biosynthetic pathways containing multiple core enzymes have potential to produce structurally complex natural products. Here we mined a fungal gene cluster that contains two predicted terpene cyclases (TCs) and a nonribosomal peptide synthetase (NRPS). We showed the flv pathway produces flavunoidine 1, an alkaloidal terpenoid. The core of 1 is a tetracyclic, cage-like, and oxygenated sesquiterpene that is connected to dimethylcadaverine via a C-N bond and is acylated with 5,5-dimethyl-l-pipecolate. The roles of all flv enzymes are established on the basis of metabolite analysis from heterologous expression.
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Affiliation(s)
| | | | - Wei Cheng
- State Key Laboratory of Natural and Biomimetic Drugs , Peking University , Beijing 100191 , China
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42
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Greene BL, Stubbe J, Nocera DG. Selenocysteine Substitution in a Class I Ribonucleotide Reductase. Biochemistry 2019; 58:5074-5084. [PMID: 31774661 DOI: 10.1021/acs.biochem.9b00973] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Ribonucleotide reductases (RNRs) employ a complex radical-based mechanism during nucleotide reduction involving multiple active site cysteines that both activate the substrate and reduce it. Using an engineered allo-tRNA, we substituted two active site cysteines with distinct function in the class Ia RNR of Escherichia coli for selenocysteine (U) via amber codon suppression, with efficiency and selectivity enabling biochemical and biophysical studies. Examination of the interactions of the C439U α2 mutant protein with nucleotide substrates and the cognate β2 subunit demonstrates that the endogenous Y122• of β2 is reduced under turnover conditions, presumably through radical transfer to form a transient U439• species. This putative U439• species is formed in a kinetically competent fashion but is incapable of initiating nucleotide reduction via 3'-H abstraction. An analogous C225U α2 protein is also capable of radical transfer from Y122•, but the radical-based substrate chemistry partitions between turnover and stalled reduction akin to the reactivity of mechanism-based inhibitors of RNR. The results collectively demonstrate the essential role of cysteine redox chemistry in the class I RNRs and establish a new tool for investigating thiyl radical reactivity in biology.
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Affiliation(s)
- Brandon L Greene
- Department of Chemistry and Biochemistry , University of California, Santa Barbara , Santa Barbara , California 93106 , United States
| | | | - Daniel G Nocera
- Department of Chemistry and Chemical Biology , Harvard University , Cambridge , Massachusetts 02138 , United States
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43
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Schöneich C. Thiyl Radical Reactions in the Chemical Degradation of Pharmaceutical Proteins. Molecules 2019; 24:E4357. [PMID: 31795282 PMCID: PMC6930596 DOI: 10.3390/molecules24234357] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Revised: 11/16/2019] [Accepted: 11/18/2019] [Indexed: 01/01/2023] Open
Abstract
Free radical pathways play a major role in the degradation of protein pharmaceuticals. Inspired by biochemical reactions carried out by thiyl radicals in various enzymatic processes, this review focuses on the role of thiyl radicals in pharmaceutical protein degradation through hydrogen atom transfer, electron transfer, and addition reactions. These processes can lead to the epimerization of amino acids, as well as the formation of various cleavage products and cross-links. Examples are presented for human insulin, human and mouse growth hormone, and monoclonal antibodies.
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Affiliation(s)
- Christian Schöneich
- Department of Pharmaceutical Chemistry, University of Kansas, 2093 Constant Avenue, Lawrence, KS 66047, USA
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44
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Ravcheev DA, Moussu L, Smajic S, Thiele I. Comparative Genomic Analysis Reveals Novel Microcompartment-Associated Metabolic Pathways in the Human Gut Microbiome. Front Genet 2019; 10:636. [PMID: 31333721 PMCID: PMC6620236 DOI: 10.3389/fgene.2019.00636] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2019] [Accepted: 06/18/2019] [Indexed: 12/16/2022] Open
Abstract
Bacterial microcompartments are self-assembling subcellular structures surrounded by a semipermeable protein shell and found only in bacteria, but not archaea or eukaryotes. The general functions of the bacterial microcompartments are to concentrate enzymes, metabolites, and cofactors for multistep pathways; maintain the cofactor ratio; protect the cell from toxic metabolic intermediates; and protect the encapsulated pathway from unwanted side reactions. The bacterial microcompartments were suggested to play a significant role in organisms of the human gut microbiome, especially for various pathogens. Here, we used a comparative genomics approach to analyze the bacterial microcompartments in 646 individual genomes of organisms commonly found in the human gut microbiome. The bacterial microcompartments were found in 150 (23.2%) analyzed genomes. These microcompartments include previously known ones for the utilization of ethanolamine, 1,2-propanediol, choline, and fucose/rhamnose. Moreover, we reconstructed two novel pathways associated with the bacterial microcompartments. These pathways are catabolic pathways for the utilization of 1-amino-2-propanol/1-amino-2-propanone and xanthine. Remarkably, the xanthine utilization pathway does not demonstrate similarity to previously known microcompartment-associated pathways. Thus, we describe a novel type of bacterial microcompartment.
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Affiliation(s)
- Dmitry A Ravcheev
- School of Medicine, National University of Ireland, Galway, University Road, Galway, Ireland.,Luxembourg Centre for Systems Biomedicine, University of Luxembourg, Esch-sur-Alzette, Luxembourg
| | - Lubin Moussu
- Luxembourg Centre for Systems Biomedicine, University of Luxembourg, Esch-sur-Alzette, Luxembourg
| | - Semra Smajic
- Luxembourg Centre for Systems Biomedicine, University of Luxembourg, Esch-sur-Alzette, Luxembourg
| | - Ines Thiele
- School of Medicine, National University of Ireland, Galway, University Road, Galway, Ireland.,Luxembourg Centre for Systems Biomedicine, University of Luxembourg, Esch-sur-Alzette, Luxembourg.,Discipline of Microbiology, School of Natural Sciences, National University of Ireland, Galway, University Road, Galway, Ireland
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45
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Bowman SEJ, Backman LRF, Bjork RE, Andorfer MC, Yori S, Caruso A, Stultz CM, Drennan CL. Solution structure and biochemical characterization of a spare part protein that restores activity to an oxygen-damaged glycyl radical enzyme. J Biol Inorg Chem 2019; 24:817-829. [PMID: 31250200 DOI: 10.1007/s00775-019-01681-2] [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: 04/30/2019] [Accepted: 06/21/2019] [Indexed: 10/26/2022]
Abstract
Glycyl radical enzymes (GREs) utilize a glycyl radical cofactor to carry out a diverse array of chemically challenging enzymatic reactions in anaerobic bacteria. Although the glycyl radical is a powerful catalyst, it is also oxygen sensitive such that oxygen exposure causes cleavage of the GRE at the site of the radical. This oxygen sensitivity presents a challenge to facultative anaerobes dwelling in areas prone to oxygen exposure. Once GREs are irreversibly oxygen damaged, cells either need to make new GREs or somehow repair the damaged one. One particular GRE, pyruvate formate lyase (PFL), can be repaired through the binding of a 14.3 kDa protein, termed YfiD, which is constitutively expressed in E. coli. Herein, we have solved a solution structure of this 'spare part' protein using nuclear magnetic resonance spectroscopy. These data, coupled with data from circular dichroism, indicate that YfiD has an inherently flexible N-terminal region (residues 1-60) that is followed by a C-terminal region (residues 72-127) that has high similarity to the glycyl radical domain of PFL. Reconstitution of PFL activity requires that YfiD binds within the core of the PFL barrel fold; however, modeling suggests that oxygen-damaged, i.e. cleaved, PFL cannot fully accommodate YfiD. We further report that a PFL variant that mimics the oxygen-damaged enzyme is highly susceptible to proteolysis, yielding additionally truncated forms of PFL. One such PFL variant of ~ 77 kDa makes an ideal scaffold for the accommodation of YfiD. A molecular model for the rescue of PFL activity by YfiD is presented.
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Affiliation(s)
- Sarah E J Bowman
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Building 68-680, Cambridge, MA, 02139, USA.,Department of Chemistry, Massachusetts Institute of Technology, Building 68-680, Cambridge, MA, 02139, USA.,Hauptman-Woodward Medical Research Institute, Buffalo, NY, 14203, USA
| | - Lindsey R F Backman
- Department of Chemistry, Massachusetts Institute of Technology, Building 68-680, Cambridge, MA, 02139, USA.,MIT Summer Research Program (MSRP), Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Rebekah E Bjork
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Building 68-680, Cambridge, MA, 02139, USA
| | - Mary C Andorfer
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Building 68-680, Cambridge, MA, 02139, USA.,Department of Biology, Massachusetts Institute of Technology, Building 68-680, Cambridge, MA, 02139, USA
| | - Santiago Yori
- MIT Summer Research Program (MSRP), Massachusetts Institute of Technology, Cambridge, MA, 02139, USA.,Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, CA, 94720, USA
| | - Alessio Caruso
- MIT Summer Research Program (MSRP), Massachusetts Institute of Technology, Cambridge, MA, 02139, USA.,Department of Chemistry, Princeton University, Princeton, NJ, 08544, USA
| | - Collin M Stultz
- Electrical Engineering and Computer Science and Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA, 02319, USA.,Division of Cardiovascular Medicine, Massachusetts General Hospital, Boston, MA, 02114, USA
| | - Catherine L Drennan
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Building 68-680, Cambridge, MA, 02139, USA. .,Department of Chemistry, Massachusetts Institute of Technology, Building 68-680, Cambridge, MA, 02139, USA. .,Department of Biology, Massachusetts Institute of Technology, Building 68-680, Cambridge, MA, 02139, USA. .,Center for Environmental Health, Massachusetts Institute of Technology, Building 68-680, Cambridge, MA, 02139, USA.
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46
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Walsh CT. Biologically generated carbon dioxide: nature's versatile chemical strategies for carboxy lyases. Nat Prod Rep 2019; 37:100-135. [PMID: 31074473 DOI: 10.1039/c9np00015a] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Covering: up to 2019Metabolic production of CO2 is natural product chemistry on a mammoth scale. Just counting humans, among all other respiring organisms, the seven billion people on the planet exhale about 3 billion tons of CO2 per year. Essentially all of the biogenic CO2 arises by action of discrete families of decarboxylases. The mechanistic routes to CO2 release from carboxylic acid metabolites vary with the electronic demands and structures of specific substrates and illustrate the breadth of chemistry employed for C-COO (C-C bond) disconnections. Most commonly decarboxylated are α-keto acid and β-keto acid substrates, the former requiring thiamin-PP as cofactor, the latter typically cofactor-free. The extensive decarboxylation of amino acids, e.g. to neurotransmitter amines, is synonymous with the coenzyme form of vitamin B6, pyridoxal-phosphate, although covalent N-terminal pyruvamide residues serve in some amino acid decarboxylases. All told, five B vitamins (B1, B2, B3, B6, B7), ATP, S-adenosylmethionine, manganese and zinc ions are pressed into service for specific decarboxylase catalyses. There are additional cofactor-independent decarboxylases that operate by distinct chemical routes. Finally, while most decarboxylases use heterolytic ionic mechanisms, a small number of decarboxylases carry out radical pathways.
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47
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Hanževački M, Čondić-Jurkić K, Banhatti RD, Smith AS, Smith DM. The Influence of Chemical Change on Protein Dynamics: A Case Study with Pyruvate Formate-Lyase. Chemistry 2019; 25:8741-8753. [PMID: 30901109 DOI: 10.1002/chem.201900663] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Indexed: 12/15/2022]
Abstract
Pyruvate formate-lyase (PFL) catalyzes the reversible conversion of pyruvate and coenzyme A (CoA) into formate and acetyl-CoA in two half-reactions. For the second half-reaction to take place, the S-H group of CoA must enter the active site of the enzyme to retrieve a protein-bound acetyl group. However, CoA is bound at the protein surface, whereas the active site is buried in the protein interior, some 20-30 Å away. The PFL system was therefore subjected to a series of extensive molecular dynamics simulations (in the μs range) and a host of advanced analysis procedures. Models representing PFL before and after the first half-reaction were used to examine the possible effect of enzyme acetylation. All simulated structures were found to be relatively stable compared to the initial crystal structure. Although the adenine portion of CoA remained predominantly bound at the protein surface, the binding of the S-H group was significantly more labile. A potential entry channel for CoA, which would allow the S-H group to reach the active site, was identified and characterized. The channel was found to be associated with accentuated fluctuations and a higher probability of being in an open state in acetylated systems. This result suggests that the acetylation of the enzyme assumes a prominent functional role, whereby the formation of the acyl intermediate serves to initiate a subtle signaling cascade that influences the protein dynamics and facilitates the entry of the second substrate.
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Affiliation(s)
- Marko Hanževački
- Division of Physical Chemistry, Ruđer Bošković Institute, Bijenička 54, Zagreb, Croatia.,PULS Group, Institute for Theoretical Physics, FAU Erlangen-Nürnberg, Staudtstraße 7, Erlangen, Germany
| | - Karmen Čondić-Jurkić
- Division of Physical Chemistry, Ruđer Bošković Institute, Bijenička 54, Zagreb, Croatia
| | - Radha Dilip Banhatti
- Division of Physical Chemistry, Ruđer Bošković Institute, Bijenička 54, Zagreb, Croatia
| | - Ana-Sunčana Smith
- Division of Physical Chemistry, Ruđer Bošković Institute, Bijenička 54, Zagreb, Croatia.,PULS Group, Institute for Theoretical Physics, FAU Erlangen-Nürnberg, Staudtstraße 7, Erlangen, Germany
| | - David M Smith
- Division of Physical Chemistry, Ruđer Bošković Institute, Bijenička 54, Zagreb, Croatia
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48
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Buckel W. Enzymatic Reactions Involving Ketyls: From a Chemical Curiosity to a General Biochemical Mechanism. Biochemistry 2019; 58:5221-5233. [PMID: 30995029 DOI: 10.1021/acs.biochem.9b00171] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Ketyls are radical anions with nucleophilic properties. Ketyls obtained by enzymatic one-electron reduction of thioesters were proposed as intermediates for the dehydration of (R)-2-hydroxyacyl-CoA to (E)-2-enoyl-CoA. This concept was extended to the Birch-like reduction of benzoyl-CoA to 1,5-cyclohexadienecarboxyl-CoA. Nature uses two methods to achieve the therefore required low reduction potentials of less than -600 mV, either by an ATP-driven electron transfer similar to that catalyzed by the iron protein of nitrogenase or by electron bifurcation. Ketyls formed by thiyl radical-initiated oxidation of alcohols followed by deprotonation are involved in coenzyme B12-independent diol dehydratases, other glycyl radical enzymes mediating key reactions in the degradations of choline, taurine, and 4-hydroxyproline, and all three classes of ribonucleotide reductases. A special case is the dehydration of 4-hydroxybutyryl-CoA to crotonyl-CoA, which most likely proceeds via an oxidation to an allylic ketyl but requires neither a strong reductant nor an external radical generator.
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Affiliation(s)
- Wolfgang Buckel
- Fachbereich Biologie , Philipps-Universität , 35032 Marburg , Germany
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49
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Xing M, Wei Y, Zhou Y, Zhang J, Lin L, Hu Y, Hua G, N Nanjaraj Urs A, Liu D, Wang F, Guo C, Tong Y, Li M, Liu Y, Ang EL, Zhao H, Yuchi Z, Zhang Y. Radical-mediated C-S bond cleavage in C2 sulfonate degradation by anaerobic bacteria. Nat Commun 2019; 10:1609. [PMID: 30962433 PMCID: PMC6453916 DOI: 10.1038/s41467-019-09618-8] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2019] [Accepted: 03/21/2019] [Indexed: 12/18/2022] Open
Abstract
Bacterial degradation of organosulfonates plays an important role in sulfur recycling, and has been extensively studied. However, this process in anaerobic bacteria especially gut bacteria is little known despite of its potential significant impact on human health with the production of toxic H2S. Here, we describe the structural and biochemical characterization of an oxygen-sensitive enzyme that catalyzes the radical-mediated C-S bond cleavage of isethionate to form sulfite and acetaldehyde. We demonstrate its involvement in pathways that enables C2 sulfonates to be used as terminal electron acceptors for anaerobic respiration in sulfate- and sulfite-reducing bacteria. Furthermore, it plays a key role in converting bile salt-derived taurine into H2S in the disease-associated gut bacterium Bilophila wadsworthia. The enzymes and transporters in these anaerobic pathways expand our understanding of microbial sulfur metabolism, and help deciphering the complex web of microbial pathways involved in the transformation of sulfur compounds in the gut. The C2 sulfonates taurine and isethionate are also present in the anaerobic mammalian gut, where they are converted into toxic H2S by sulfate and sulfite-reducing bacteria. Here the authors characterise the O2-sensitive enzyme IseG that catalyzes the C-S bond cleavage of isethionate and show that IseG also plays a key role in converting taurine into H2S in Bilophila wadsworthia.
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Affiliation(s)
- Meining Xing
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency, Collaborative Innovation Center of Chemical Science and Engineering, School of Pharmaceutical Science and Technology, Tianjin University, 300072, Tianjin, China
| | - Yifeng Wei
- Metabolic Engineering Research Laboratory, Institute of Chemical and Engineering Sciences, Agency for Science, Technology and Research (A*STAR), Singapore, 138669, Singapore
| | - Yan Zhou
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency, Collaborative Innovation Center of Chemical Science and Engineering, School of Pharmaceutical Science and Technology, Tianjin University, 300072, Tianjin, China
| | - Jun Zhang
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency, Collaborative Innovation Center of Chemical Science and Engineering, School of Pharmaceutical Science and Technology, Tianjin University, 300072, Tianjin, China
| | - Lianyun Lin
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency, Collaborative Innovation Center of Chemical Science and Engineering, School of Pharmaceutical Science and Technology, Tianjin University, 300072, Tianjin, China
| | - Yiling Hu
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency, Collaborative Innovation Center of Chemical Science and Engineering, School of Pharmaceutical Science and Technology, Tianjin University, 300072, Tianjin, China
| | - Gaoqun Hua
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency, Collaborative Innovation Center of Chemical Science and Engineering, School of Pharmaceutical Science and Technology, Tianjin University, 300072, Tianjin, China
| | - Ankanahalli N Nanjaraj Urs
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency, Collaborative Innovation Center of Chemical Science and Engineering, School of Pharmaceutical Science and Technology, Tianjin University, 300072, Tianjin, China
| | - Dazhi Liu
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency, Collaborative Innovation Center of Chemical Science and Engineering, School of Pharmaceutical Science and Technology, Tianjin University, 300072, Tianjin, China
| | - Feifei Wang
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency, Collaborative Innovation Center of Chemical Science and Engineering, School of Pharmaceutical Science and Technology, Tianjin University, 300072, Tianjin, China
| | - Cuixia Guo
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency, Collaborative Innovation Center of Chemical Science and Engineering, School of Pharmaceutical Science and Technology, Tianjin University, 300072, Tianjin, China
| | - Yang Tong
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency, Collaborative Innovation Center of Chemical Science and Engineering, School of Pharmaceutical Science and Technology, Tianjin University, 300072, Tianjin, China
| | - Mengya Li
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency, Collaborative Innovation Center of Chemical Science and Engineering, School of Pharmaceutical Science and Technology, Tianjin University, 300072, Tianjin, China
| | - Yanhong Liu
- Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, 100190, China
| | - Ee Lui Ang
- Metabolic Engineering Research Laboratory, Institute of Chemical and Engineering Sciences, Agency for Science, Technology and Research (A*STAR), Singapore, 138669, Singapore
| | - Huimin Zhao
- Metabolic Engineering Research Laboratory, Institute of Chemical and Engineering Sciences, Agency for Science, Technology and Research (A*STAR), Singapore, 138669, Singapore. .,Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, IL, 61801, USA.
| | - Zhiguang Yuchi
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency, Collaborative Innovation Center of Chemical Science and Engineering, School of Pharmaceutical Science and Technology, Tianjin University, 300072, Tianjin, China.
| | - Yan Zhang
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency, Collaborative Innovation Center of Chemical Science and Engineering, School of Pharmaceutical Science and Technology, Tianjin University, 300072, Tianjin, China.
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50
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A glycyl radical enzyme enables hydrogen sulfide production by the human intestinal bacterium Bilophila wadsworthia. Proc Natl Acad Sci U S A 2019; 116:3171-3176. [PMID: 30718429 PMCID: PMC6386719 DOI: 10.1073/pnas.1815661116] [Citation(s) in RCA: 97] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
This paper describes a pathway for anaerobic bacterial metabolism of taurine (2-aminoethanesulfonate), an abundant substrate in the human intestinal microbiota, by the intestinal bacterium and opportunistic pathogen, Bilophila wadsworthia. This metabolism converts taurine to the toxic metabolite hydrogen sulfide (H2S), an activity associated with inflammatory bowel disease and colorectal cancer. A critical enzyme in this pathway is isethionate sulfite-lyase, a member of the glycyl radical enzyme family. This enzyme catalyzes a novel, radical-based C-S bond-cleavage reaction to convert isethionate (2-hydroxyethanesulfonate) to sulfite and acetaldehyde. This discovery improves our understanding of H2S production in the human body and may also offer new approaches for controlling intestinal H2S production and B. wadsworthia infections. Hydrogen sulfide (H2S) production in the intestinal microbiota has many contributions to human health and disease. An important source of H2S in the human gut is anaerobic respiration of sulfite released from the abundant dietary and host-derived organic sulfonate substrate in the gut, taurine (2-aminoethanesulfonate). However, the enzymes that allow intestinal bacteria to access sulfite from taurine have not yet been identified. Here we decipher the complete taurine desulfonation pathway in Bilophila wadsworthia 3.1.6 using differential proteomics, in vitro reconstruction with heterologously produced enzymes, and identification of critical intermediates. An initial deamination of taurine to sulfoacetaldehyde by a known taurine:pyruvate aminotransferase is followed, unexpectedly, by reduction of sulfoacetaldehyde to isethionate (2-hydroxyethanesulfonate) by an NADH-dependent reductase. Isethionate is then cleaved to sulfite and acetaldehyde by a previously uncharacterized glycyl radical enzyme (GRE), isethionate sulfite-lyase (IslA). The acetaldehyde produced is oxidized to acetyl-CoA by a dehydrogenase, and the sulfite is reduced to H2S by dissimilatory sulfite reductase. This unique GRE is also found in Desulfovibrio desulfuricans DSM642 and Desulfovibrio alaskensis G20, which use isethionate but not taurine; corresponding knockout mutants of D. alaskensis G20 did not grow with isethionate as the terminal electron acceptor. In conclusion, the novel radical-based C-S bond-cleavage reaction catalyzed by IslA diversifies the known repertoire of GRE superfamily enzymes and enables the energy metabolism of B. wadsworthia. This GRE is widely distributed in gut bacterial genomes and may represent a novel target for control of intestinal H2S production.
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