1
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Yang H, Ho MB, Lundahl MN, Mosquera MA, Broderick WE, Broderick JB, Hoffman BM. ENDOR Spectroscopy Reveals the "Free" 5'-Deoxyadenosyl Radical in a Radical SAM Enzyme Active Site Actually is Chaperoned by Close Interaction with the Methionine-Bound [4Fe-4S] 2+ Cluster. J Am Chem Soc 2024; 146:3710-3720. [PMID: 38308759 DOI: 10.1021/jacs.3c09428] [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: 02/05/2024]
Abstract
1/2H and 13C hyperfine coupling constants to 5'-deoxyadenosyl (5'-dAdo•) radical trapped within the active site of the radical S-adenosyl-l-methionine (SAM) enzyme, pyruvate formate lyase-activating enzyme (PFL-AE), both in the absence of substrate and the presence of a reactive peptide-model of the PFL substrate, are completely characteristic of a classical organic free radical whose unpaired electron is localized in the 2pπ orbital of the sp2 C5'-carbon (J. Am. Chem. Soc. 2019, 141, 12139-12146). However, prior electron-nuclear double resonance (ENDOR) measurements had indicated that this 5'-dAdo• free radical is never truly "free": tight van der Waals contact with its target partners and active-site residues guide it in carrying out the exquisitely precise, regioselective reactions that are hallmarks of RS enzymes. Here, our understanding of how the active site chaperones 5'-dAdo• is extended through the finding that this apparently unexceptional organic free radical has an anomalous g-tensor and exhibits significant 57Fe, 13C, 15N, and 2H hyperfine couplings to the adjacent, isotopically labeled, methionine-bound [4Fe-4S]2+ cluster cogenerated with 5'-dAdo• during homolytic cleavage of cluster-bound SAM. The origin of the 57Fe couplings through nonbonded radical-cluster contact is illuminated by a formal exchange-coupling model and broken symmetry-density functional theory computations. Incorporation of ENDOR-derived distances from C5'(dAdo•) to labeled-methionine as structural constraints yields a model for active-site positioning of 5'-dAdo• with a short, nonbonded C5'-Fe distance (∼3 Å). This distance involves substantial motion of 5'-dAdo• toward the unique Fe of the [4Fe-4S]2+ cluster upon S-C(5') bond-cleavage, plausibly an initial step toward formation of the Fe-C5' bond of the organometallic complex, Ω, the central intermediate in catalysis by radical-SAM enzymes.
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Affiliation(s)
- Hao Yang
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Madeline B Ho
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Maike N Lundahl
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States
| | - Martín A Mosquera
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States
| | - William E Broderick
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States
| | - Joan B Broderick
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States
| | - Brian M Hoffman
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
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2
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Lachowicz J, Lee J, Sagatova A, Jew K, Grove TL. The new epoch of structural insights into radical SAM enzymology. Curr Opin Struct Biol 2023; 83:102720. [PMID: 37862762 DOI: 10.1016/j.sbi.2023.102720] [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: 07/13/2023] [Revised: 09/21/2023] [Accepted: 09/22/2023] [Indexed: 10/22/2023]
Abstract
The Radical SAM (RS) superfamily of enzymes catalyzes a wide array of enzymatic reactions. The majority of these enzymes employ an electron from a reduced [4Fe-4S]+1 cluster to facilitate the reductive cleavage of S-adenosyl-l-methionine, thereby producing a highly reactive 5'-deoxyadenosyl radical (5'-dA⋅) and l-methionine. Typically, RS enzymes use this 5'-dA⋅ to extract a hydrogen atom from the target substrate, starting the cascade of an expansive and impressive variety of chemical transformations. While a great deal of understanding has been gleaned for 5'-dA⋅ formation, because of the chemical diversity within this superfamily, the subsequent chemical transformations have only been fully elucidated in a few examples. In addition, with the advent of new sequencing technology, the size of this family now surpasses 700,000 members, with the number of uncharacterized enzymes and domains also rapidly expanding. In this review, we outline the history of RS enzyme characterization in what we term "epochs" based on advances in technology designed for stably producing these enzymes in an active state. We propose that the state of the field has entered the fourth epoch, which we argue should commence with a protein structure initiative focused solely on RS enzymes to properly tackle this unique superfamily and uncover more novel chemical transformations that likely exist.
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Affiliation(s)
- Jake Lachowicz
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - James Lee
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Alia Sagatova
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Kristen Jew
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Tyler L Grove
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
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3
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Broderick JB, Broderick WE, Hoffman BM. Radical SAM enzymes: Nature's choice for radical reactions. FEBS Lett 2023; 597:92-101. [PMID: 36251330 PMCID: PMC9894703 DOI: 10.1002/1873-3468.14519] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Accepted: 10/05/2022] [Indexed: 02/04/2023]
Abstract
Enzymes that use a [4Fe-4S]1+ cluster plus S-adenosyl-l-methionine (SAM) to initiate radical reactions (radical SAM) form the largest enzyme superfamily, with over half a million members across the tree of life. This review summarizes recent work revealing the radical SAM reaction pathway, which ultimately liberates the 5'-deoxyadenosyl (5'-dAdo•) radical to perform extremely diverse, highly regio- and stereo-specific, transformations. Most surprising was the discovery of an organometallic intermediate Ω exhibiting an Fe-C5'-adenosyl bond. Ω liberates 5'-dAdo• through homolysis of the Fe-C5' bond, in analogy to Co-C5' bond homolysis in B12 , previously viewed as biology's paradigmatic radical generator. The 5'-dAdo• has been trapped and characterized in radical SAM enzymes via a recently discovered photoreactivity of the [4Fe-4S]+ /SAM complex, and has been confirmed as a catalytically active intermediate in enzyme catalysis. The regioselective SAM S-C bond cleavage to produce 5'-dAdo• originates in the Jahn-Teller effect. The simplicity of SAM as a radical precursor, and the exquisite control of 5'-dAdo• reactivity in radical SAM enzymes, may be why radical SAM enzymes pervade the tree of life, while B12 enzymes are only a few.
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Affiliation(s)
- Joan B. Broderick
- Department of Chemistry & Biochemistry, 103 CBB, Montana State University, Bozeman, MT 59717
| | - William E. Broderick
- Department of Chemistry & Biochemistry, 103 CBB, Montana State University, Bozeman, MT 59717
| | - Brian M. Hoffman
- Department of Chemistry, 2145 Sheridan Rd, Northwestern University, Evanston, IL. 60208
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4
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Dill Z, Li B, Bridwell-Rabb J. Purification and structural elucidation of a cobalamin-dependent radical SAM enzyme. Methods Enzymol 2022; 669:91-116. [PMID: 35644182 DOI: 10.1016/bs.mie.2021.12.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
The cobalamin (Cbl)-dependent radical S-adenosylmethionine (SAM) enzymes use a [4Fe-4S] cluster, SAM, and Cbl to carry out remarkable catalytic feats in a large number of biosynthetic pathways. However, despite the abundance of annotated Cbl-dependent radical SAM enzymes, relatively few molecular details exist regarding how these enzymes function. Traditionally, challenges associated with purifying and reconstituting Cbl-dependent radical SAM enzymes have hindered biochemical studies aimed at elucidating the structures and mechanisms of these enzymes. Herein, we describe a bottom-up approach that was used to crystallize OxsB, learn about the overall architecture of a Cbl-dependent radical SAM enzyme, and facilitate mechanistic studies. We report lessons learned from the crystallization of different states of OxsB, including the apo-, selenomethionine (SeMet)-labeled, and fully reconstituted form of OxsB that has a [4Fe-4S] cluster, SAM, and Cbl bound. Further, we suggest that, when appropriate, this bottom-up method can be used to facilitate studies on enzymes in this class for which there are challenges associated with purifying and reconstituting the active enzyme.
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Affiliation(s)
- Zerick Dill
- Department of Chemistry, University of Michigan, Ann Arbor, MI, United States; Program in Chemical Biology, University of Michigan, Ann Arbor, MI, United States
| | - Bin Li
- Department of Chemistry, University of Michigan, Ann Arbor, MI, United States
| | - Jennifer Bridwell-Rabb
- Department of Chemistry, University of Michigan, Ann Arbor, MI, United States; Program in Chemical Biology, University of Michigan, Ann Arbor, MI, United States.
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5
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Zhang J, Hou X, Chen Z, Ko Y, Ruszczycky MW, Chen Y, Zhou J, Liu HW. Dioxane Bridge Formation during the Biosynthesis of Spectinomycin Involves a Twitch Radical S-Adenosyl Methionine Dehydrogenase That May Have Evolved from an Epimerase. J Am Chem Soc 2022; 144:9910-9919. [PMID: 35622017 DOI: 10.1021/jacs.2c02676] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Spectinomycin is a dioxane-bridged, tricyclic aminoglycoside produced by Streptomyces spectabilis ATCC 27741. While the spe biosynthetic gene cluster for spectinomycin has been reported, the chemistry underlying construction of the dioxane ring is unknown. The twitch radical SAM enzyme SpeY from the spe cluster is shown here to catalyze dehydrogenation of the C2' alcohol of (2'R,3'S)-tetrahydrospectinomycin to yield (3'S)-dihydrospectinomycin as a likely biosynthetic intermediate. This reaction is radical-mediated and initiated via H atom abstraction from C2' of the substrate by the 5'-deoxyadenosyl radical equivalent generated upon reductive cleavage of SAM. Crystallographic analysis of the ternary Michaelis complex places serine-183 adjacent to C2' of the bound substrate opposite C5' of SAM. Mutation of this residue to cysteine converts SpeY to the corresponding C2' epimerase mirroring the opposite phenomenon observed in the homologous twitch radical SAM epimerase HygY from the hygromycin B biosynthetic pathway. Phylogenetic analysis suggests a relatively recent evolutionary branching of putative twitch radical SAM epimerases bearing homologous cysteine residues to generate the SpeY clade of enzymes.
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Affiliation(s)
- Jiawei Zhang
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
| | - Xueli Hou
- Shaanxi Key Laboratory of Natural Products & Chemical Biology, College of Chemistry & Pharmacy, Northwest A&F University, Yangling 712100, Shaanxi, China.,State Key Laboratory of Bioorganic and Natural Products Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China
| | - Zhang Chen
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
| | - Yeonjin Ko
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
| | - Mark W Ruszczycky
- Division of Chemical Biology & Medicinal Chemistry, College of Pharmacy, University of Texas at Austin, Austin, Texas 78712, United States
| | - Yutian Chen
- Division of Chemical Biology & Medicinal Chemistry, College of Pharmacy, University of Texas at Austin, Austin, Texas 78712, United States
| | - Jiahai Zhou
- State Key Laboratory of Bioorganic and Natural Products Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China.,CAS Key Laboratory of Quantitative Engineering Biology, Shenzhen Institute of Synthetic Biology, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
| | - Hung-Wen Liu
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States.,Division of Chemical Biology & Medicinal Chemistry, College of Pharmacy, University of Texas at Austin, Austin, Texas 78712, United States
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6
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Lundahl MN, Sarksian R, Yang H, Jodts RJ, Pagnier A, Smith DF, Mosquera MA, van der Donk WA, Hoffman BM, Broderick WE, Broderick JB. Mechanism of Radical S-Adenosyl-l-methionine Adenosylation: Radical Intermediates and the Catalytic Competence of the 5'-Deoxyadenosyl Radical. J Am Chem Soc 2022; 144:5087-5098. [PMID: 35258967 PMCID: PMC9524473 DOI: 10.1021/jacs.1c13706] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Radical S-adenosyl-l-methionine (SAM) enzymes employ a [4Fe-4S] cluster and SAM to initiate diverse radical reactions via either H-atom abstraction or substrate adenosylation. Here we use freeze-quench techniques together with electron paramagnetic resonance (EPR) spectroscopy to provide snapshots of the reaction pathway in an adenosylation reaction catalyzed by the radical SAM enzyme pyruvate formate-lyase activating enzyme on a peptide substrate containing a dehydroalanine residue in place of the target glycine. The reaction proceeds via the initial formation of the organometallic intermediate Ω, as evidenced by the characteristic EPR signal with g∥ = 2.035 and g⊥ = 2.004 observed when the reaction is freeze-quenched at 500 ms. Thermal annealing of frozen Ω converts it into a second paramagnetic species centered at giso = 2.004; this second species was generated directly using freeze-quench at intermediate times (∼8 s) and unequivocally identified via isotopic labeling and EPR spectroscopy as the tertiary peptide radical resulting from adenosylation of the peptide substrate. An additional paramagnetic species observed in samples quenched at intermediate times was revealed through thermal annealing while frozen and spectral subtraction as the SAM-derived 5'-deoxyadenosyl radical (5'-dAdo•). The time course of the 5'-dAdo• and tertiary peptide radical EPR signals reveals that the former generates the latter. These results thus support a mechanism in which Ω liberates 5'-dAdo• by Fe-C5' bond homolysis, and the 5'-dAdo• attacks the dehydroalanine residue of the peptide substrate to form the adenosylated peptide radical species. The results thus provide a picture of a catalytically competent 5'-dAdo• intermediate trapped just prior to reaction with the substrate.
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Affiliation(s)
- Maike N. Lundahl
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States
| | - Raymond Sarksian
- Department of Chemistry and Howard Hughes Medical Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Hao Yang
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Richard J. Jodts
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Adrien Pagnier
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States
| | - Donald F. Smith
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States
| | - Martín A. Mosquera
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States
| | - Wilfred A. van der Donk
- Department of Chemistry and Howard Hughes Medical Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Brian M. Hoffman
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - William E. Broderick
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States
| | - Joan B. Broderick
- Corresponding Author: Joan B. Broderick – Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States;
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7
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Lee YH, Hou X, Chen R, Feng J, Liu X, Ruszczycky MW, Gao JM, Wang B, Zhou J, Liu HW. Radical S-Adenosyl Methionine Enzyme BlsE Catalyzes a Radical-Mediated 1,2-Diol Dehydration during the Biosynthesis of Blasticidin S. J Am Chem Soc 2022; 144:4478-4486. [PMID: 35238201 DOI: 10.1021/jacs.1c12010] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The biosynthesis of blasticidin S has drawn attention due to the participation of the radical S-adenosyl methionine (SAM) enzyme BlsE. The original assignment of BlsE as a radical-mediated, redox-neutral decarboxylase is unusual because this reaction appears to serve no biosynthetic purpose and would need to be reversed by a subsequent carboxylation step. Furthermore, with the exception of BlsE, all other radical SAM decarboxylases reported to date are oxidative in nature. Careful analysis of the BlsE reaction, however, demonstrates that BlsE is not a decarboxylase but instead a lyase that catalyzes the dehydration of cytosylglucuronic acid (CGA) to form cytosyl-4'-keto-3'-deoxy-d-glucuronic acid, which can rapidly decarboxylate nonenzymatically in vitro. Analysis of substrate isotopologs, fluorinated analogues, as well as computational models based on X-ray crystal structures of the BlsE·SAM (2.09 Å) and BlsE·SAM·CGA (2.62 Å) complexes suggests that BlsE catalysis likely proceeds via direct elimination of water from the CGA C4' α-hydroxyalkyl radical as opposed to 1,2-migration of the C3'-hydroxyl prior to dehydration. Biosynthetic and mechanistic implications of the revised assignment of BlsE are discussed.
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Affiliation(s)
- Yu-Hsuan Lee
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
| | - Xueli Hou
- Shaanxi Key Laboratory of Natural Products & Chemical Biology, College of Chemistry & Pharmacy, Northwest A&F University, Yangling 712100, Shaanxi China.,State Key Laboratory of Bioorganic and Natural Products Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China
| | - Ridao Chen
- Division of Chemical Biology & Medicinal Chemistry, College of Pharmacy, University of Texas at Austin, Austin, Texas 78712, United States.,State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100050, China
| | - Jianqiang Feng
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Xiao Liu
- Division of Chemical Biology & Medicinal Chemistry, College of Pharmacy, University of Texas at Austin, Austin, Texas 78712, United States.,School of Chinese Materia Medica, Beijing University of Chinese Medicine, Beijing 100029, China
| | - Mark W Ruszczycky
- Division of Chemical Biology & Medicinal Chemistry, College of Pharmacy, University of Texas at Austin, Austin, Texas 78712, United States
| | - Jin-Ming Gao
- Shaanxi Key Laboratory of Natural Products & Chemical Biology, College of Chemistry & Pharmacy, Northwest A&F University, Yangling 712100, Shaanxi China
| | - Binju Wang
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Jiahai Zhou
- State Key Laboratory of Bioorganic and Natural Products Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China.,CAS Key Laboratory of Quantitative Engineering Biology, Shenzhen Institute of Synthetic Biology, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
| | - Hung-Wen Liu
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States.,Division of Chemical Biology & Medicinal Chemistry, College of Pharmacy, University of Texas at Austin, Austin, Texas 78712, United States
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8
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Besandre RA, Chen Z, Davis I, Zhang J, Ruszczycky MW, Liu A, Liu HW. HygY Is a Twitch Radical SAM Epimerase with Latent Dehydrogenase Activity Revealed upon Mutation of a Single Cysteine Residue. J Am Chem Soc 2021; 143:15152-15158. [PMID: 34491039 DOI: 10.1021/jacs.1c05727] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
HygY is a SPASM/twitch radical SAM enzyme hypothesized to catalyze the C2'-epimerization of galacamine during the biosynthesis of hygromycin B. This activity is confirmed via biochemical and structural analysis of the derivatized reaction products using chemically synthesized deuterated substrate, high-resolution mass spectrometry and 1H NMR. Electron paramagnetic resonance spectroscopy of the reduced enzyme is consistent with ligation of two [Fe4S4] clusters characteristic of the twitch radical SAM subgroup. HygY catalyzed epimerization proceeds with incorporation of a single solvent Hydron into the talamine product facilitated by the catalytic cysteine-183 residue. Mutation of this cysteine to alanine converts HygY from a C2'-epimerase to an C2'-dehydrogenase with comparable activity. The SPASM/twitch radical SAM enzymes often serve as anaerobic oxidases making the redox-neutral epimerases in this class rather interesting. The discovery of latent dehydrogenase activity in a twitch epimerase may therefore offer new insights into the mechanistic features that distinguish oxidative versus redox-neutral SPASM/twitch enzymes and lead to the evolution of new enzyme activities.
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Affiliation(s)
- Ronald A Besandre
- Department of Chemistry, University of Texas at Austin, Austin, TX 78712, United States
| | - Zhang Chen
- Department of Chemistry, University of Texas at Austin, Austin, TX 78712, United States
| | - Ian Davis
- Department of Chemistry, University of Texas at San Antonio, San Antonio, TX 78249, United States
| | - Jiawei Zhang
- Department of Chemistry, University of Texas at Austin, Austin, TX 78712, United States
| | - Mark Walter Ruszczycky
- Division of Chemical Biology and Medicinal Chemistry, College of Pharmacy, University of Texas at Austin, Austin, TX 78712, United States
| | - Aimin Liu
- Department of Chemistry, University of Texas at San Antonio, San Antonio, TX 78249, United States
| | - Hung-Wen Liu
- Department of Chemistry, University of Texas at Austin, Austin, TX 78712, United States.,Division of Chemical Biology and Medicinal Chemistry, College of Pharmacy, University of Texas at Austin, Austin, TX 78712, United States
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9
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10
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Sayler R, Stich TA, Joshi S, Cooper N, Shaw JT, Begley TP, Tantillo DJ, Britt RD. Trapping and Electron Paramagnetic Resonance Characterization of the 5'dAdo • Radical in a Radical S-Adenosyl Methionine Enzyme Reaction with a Non-Native Substrate. ACS CENTRAL SCIENCE 2019; 5:1777-1785. [PMID: 31807679 PMCID: PMC6891858 DOI: 10.1021/acscentsci.9b00706] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Indexed: 05/03/2023]
Abstract
S-Adenosyl methionine (SAM) is employed as a [4Fe-4S]-bound cofactor in the superfamily of radical SAM (rSAM) enzymes, in which one-electron reduction of the [4Fe-4S]-SAM moiety leads to homolytic cleavage of the S-adenosyl methionine to generate the 5'-deoxyadenosyl radical (5'dAdo•), a potent H-atom abstractor. HydG, a member of this rSAM family, uses the 5'dAdo• radical to lyse its substrate, tyrosine, producing CO and CN that bind to a unique Fe site of a second HydG Fe-S cluster, ultimately producing a mononuclear organometallic Fe-l-cysteine-(CO)2CN complex as an intermediate in the bioassembly of the catalytic H-cluster of [Fe-Fe] hydrogenase. Here we report the use of non-native tyrosine substrate analogues to further probe the initial radical chemistry of HydG. One such non-native substrate is 4-hydroxy phenyl propanoic acid (HPPA) which lacks the amino group of tyrosine, replacing the CαH-NH2 with a CH2 at the C2 position. Electron paramagnetic resonance (EPR) studies show the generation of a strong and relatively stable radical in the HydG reaction with natural abundance and 13C2-HPPA, with appreciable spin density localized at C2. These results led us to try parallel experiments with the more oxidized non-native substrate coumaric acid, which has a C2=C3 alkene substitution relative to HPPA's single bond. Interestingly, the HydG reaction with the cis-p-coumaric acid isomer led to the trapping of a new radical EPR signal, and EPR studies using cis-p-coumaric acid along with isotopically labeled SAM reveal that we have for the first time trapped and characterized the 5'dAdo• radical in an actual rSAM enzyme reaction, here by using this specific non-native substrate cis-p-coumaric acid. Density functional theory energetics calculations show that the cis-p-coumaric acid has approximately the same C-H bond dissociation free energy as 5'dAdo•, providing a possible explanation for our ability to trap an appreciable fraction of 5'dAdo• in this specific rSAM reaction. The radical's EPR line shape and its changes with SAM isotopic substitution are nearly identical to those of a 5'dAdo• radical recently generated by cryophotolysis of a prereduced [4Fe-4S]-SAM center in another rSAM enzyme, pyruvate formate-lyase activating enzyme, further supporting our assignment that we have indeed trapped and characterized the 5'dAdo• radical in a radical SAM enzymatic reaction by appropriate tuning of the relative radical free energies via the judicious selection of a non-native substrate.
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Affiliation(s)
- Richard
I. Sayler
- Department
of Chemistry, University of California,
Davis, Davis, California 95616, United States
| | - Troy A. Stich
- Department
of Chemistry, University of California,
Davis, Davis, California 95616, United States
| | - Sumedh Joshi
- Department
of Chemistry, Texas A&M University, College Station, Texas 77842, United States
| | - Nicole Cooper
- Department
of Chemistry, University of California,
Davis, Davis, California 95616, United States
| | - Jared T. Shaw
- Department
of Chemistry, University of California,
Davis, Davis, California 95616, United States
| | - Tadhg P. Begley
- Department
of Chemistry, Texas A&M University, College Station, Texas 77842, United States
| | - Dean J. Tantillo
- Department
of Chemistry, University of California,
Davis, Davis, California 95616, United States
| | - R. David Britt
- Department
of Chemistry, University of California,
Davis, Davis, California 95616, United States
- E-mail: . Phone: (530) 752
6377
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11
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Radical SAM enzymes: surprises along the path to understanding mechanism. J Biol Inorg Chem 2019; 24:769-776. [DOI: 10.1007/s00775-019-01706-w] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Accepted: 08/16/2019] [Indexed: 10/26/2022]
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12
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Bridwell-Rabb J, Grell TAJ, Drennan CL. A Rich Man, Poor Man Story of S-Adenosylmethionine and Cobalamin Revisited. Annu Rev Biochem 2019; 87:555-584. [PMID: 29925255 DOI: 10.1146/annurev-biochem-062917-012500] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
S-adenosylmethionine (AdoMet) has been referred to as both "a poor man's adenosylcobalamin (AdoCbl)" and "a rich man's AdoCbl," but today, with the ever-increasing number of functions attributed to each cofactor, both appear equally rich and surprising. The recent characterization of an organometallic species in an AdoMet radical enzyme suggests that the line that differentiates them in nature will be constantly challenged. Here, we compare and contrast AdoMet and cobalamin (Cbl) and consider why Cbl-dependent AdoMet radical enzymes require two cofactors that are so similar in their reactivity. We further carry out structural comparisons employing the recently determined crystal structure of oxetanocin-A biosynthetic enzyme OxsB, the first three-dimensional structural data on a Cbl-dependent AdoMet radical enzyme. We find that the structural motifs responsible for housing the AdoMet radical machinery are largely conserved, whereas the motifs responsible for binding additional cofactors are much more varied.
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Affiliation(s)
- Jennifer Bridwell-Rabb
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA; , .,Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.,Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.,Present address: Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Tsehai A J Grell
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Catherine L Drennan
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA; , .,Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.,Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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13
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Ruszczycky MW, Zhong A, Liu HW. Following the electrons: peculiarities in the catalytic cycles of radical SAM enzymes. Nat Prod Rep 2019; 35:615-621. [PMID: 29485151 DOI: 10.1039/c7np00058h] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Radical SAM enzymes use S-adenosyl-l-methionine as an oxidant to initiate radical-mediated transformations that would otherwise not be possible with Lewis acid/base chemistry alone. These reactions are either redox neutral or oxidative leading to certain expectations regarding the role of SAM as either a reusable cofactor or the ultimate electron acceptor during each turnover. However, these expectations are frequently not realized resulting in fundamental questions regarding the redox handling and movement of electrons associated with these biological catalysts. Herein we provide a focused perspective on several of these questions and associated hypotheses with an emphasis on recently discovered radical SAM enzymes.
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Affiliation(s)
- Mark W Ruszczycky
- Division of Chemical Biology & Medicinal Chemistry, College of Pharmacy, University of Texas at Austin, USA.
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14
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Mandalapu D, Ji X, Zhang Q. Reductive Cleavage of Sulfoxide and Sulfone by Two Radical S-Adenosyl-l-methionine Enzymes. Biochemistry 2018; 58:36-39. [DOI: 10.1021/acs.biochem.8b00844] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
| | - Xinjian Ji
- Department of Chemistry, Fudan University, Shanghai 200433, China
| | - Qi Zhang
- Department of Chemistry, Fudan University, Shanghai 200433, China
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15
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Gagnon DM, Stich TA, Mehta AP, Abdelwahed SH, Begley TP, Britt RD. An Aminoimidazole Radical Intermediate in the Anaerobic Biosynthesis of the 5,6-Dimethylbenzimidazole Ligand to Vitamin B12. J Am Chem Soc 2018; 140:12798-12807. [PMID: 30208703 DOI: 10.1021/jacs.8b05686] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Organisms that perform the de novo biosynthesis of cobalamin (vitamin B12) do so via unique pathways depending on the presence of oxygen in the environment. The anaerobic biosynthesis pathway of 5,6-dimethylbenzimidazole, the so-called "lower ligand" to the cobalt center, has been recently identified. This process begins with the conversion of 5-aminoimidazole ribotide (AIR) to 5-hydroxybenzimidazole (HBI) by the radical S-adenosyl-l-methionine (SAM) enzyme BzaF, also known as HBI synthase. In this work we report the characterization of a radical intermediate in the reaction of BzaF using electron paramagnetic resonance spectroscopy. Using various isotopologues of AIR, we extracted hyperfine parameters for a number of nuclei, allowing us to propose plausible chemical compositions and structures for this intermediate. Specifically, we find that an aminoimidazole radical is formed in close proximity to a fragment of the ribose ring. These findings induce the revision of past proposed mechanisms and illustrate the ability of radical SAM enzymes to tightly control the radical chemistry that they engender.
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Affiliation(s)
- Derek M Gagnon
- Department of Chemistry , University of California , Davis , California 95616 , United States
| | - Troy A Stich
- Department of Chemistry , University of California , Davis , California 95616 , United States
| | - Angad P Mehta
- Department of Chemistry , Texas A&M University , College Station , Texas 77843 , United States
| | - Sameh H Abdelwahed
- Department of Chemistry , Texas A&M University , College Station , Texas 77843 , United States
| | - Tadhg P Begley
- Department of Chemistry , Texas A&M University , College Station , Texas 77843 , United States
| | - R David Britt
- Department of Chemistry , University of California , Davis , California 95616 , United States
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16
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Jungen S, Chen P. Alkyl Radical Generation by an Intramolecular Homolytic Substitution Reaction between Iron(II) and Trialkylsulfonium Groups. Chemistry 2018; 24:11008-11020. [PMID: 29768681 DOI: 10.1002/chem.201801952] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2018] [Revised: 05/15/2018] [Indexed: 11/08/2022]
Abstract
Intramolecular, homolytic substitution reactions between iron(II) species and various trialkylsulfonium groups were directly observed in the gas phase upon collision-induced dissociation. In spite of the notoriously low reduction potential of trialkylsulfonium species and the mismatched oxidation potential of iron(II), the reactions proceed at moderate collision energies, forming an alkyl radical as well as a thioether coordinated to the iron. In contrast to classical homolytic substitutions, the attacking radical is a "metalloradical", namely iron(II) that is oxidized to iron(III) during the reaction. With this process we demonstrate that the conceptually analogous, putative radical generation step in radical S-adenosyl methionine (SAM) enzymes is possible and plausible. Further, we show that this kind of reaction only occurs in constrained systems with a defined geometry. Combining experimental measurements with DFT studies and NBO analyses allowed us to gain insights into the reactivity and transition states of these systems. Based on our findings, we challenge the notion of a collinear transition state in the radical generation step of radical SAM enzymes and propose it to be bent instead.
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Affiliation(s)
- Stefan Jungen
- Laboratorium für Organische Chemie, Eidgenössische Technische Hochschule (ETH), Zürich, Switzerland
| | - Peter Chen
- Laboratorium für Organische Chemie, Eidgenössische Technische Hochschule (ETH), Zürich, Switzerland
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17
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A B 12-dependent radical SAM enzyme involved in oxetanocin A biosynthesis. Nature 2017; 544:322-326. [PMID: 28346939 PMCID: PMC5398914 DOI: 10.1038/nature21689] [Citation(s) in RCA: 73] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Accepted: 02/03/2017] [Indexed: 11/22/2022]
Abstract
Oxetanocin-A (OXT-A, 1) is a potent antitumor, antiviral, and
antibacterial compound. Biosynthesis of OXT-A has been linked to a
plasmid-borne, Bacillus megaterium gene cluster that contains
four genes, oxsA, oxsB, oxrA,
and oxrB. Here, we show that the oxsA and
oxsB genes are both required for the production of OXT-A.
Biochemical analysis of the encoded proteins, a cobalamin (Cbl)-dependent
S-adenosylmethionine (AdoMet) radical enzyme, OxsB, and an
HD-domain phosphohydrolase, OxsA, revealed that OXT-A is derived from
2′-deoxyadenosine phosphate in an OxsB-catalyzed ring contraction
reaction initiated by H-atom abstraction from C2′. Hence, OxsB
represents the first biochemically characterized non-methylating Cbl-dependent
AdoMet radical enzyme. X-ray analysis of OxsB reveals the fold of a
Cbl-dependent AdoMet radical enzyme for which there are an estimated 7000
members. Overall, this work provides a framework for understanding the interplay
of AdoMet and Cbl cofactors and expands the catalytic repertoire of
Cbl-dependent AdoMet radical enzymes.
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18
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Vitamin B 12 in the spotlight again. Curr Opin Chem Biol 2017; 37:63-70. [PMID: 28167430 DOI: 10.1016/j.cbpa.2017.01.013] [Citation(s) in RCA: 78] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Revised: 01/07/2017] [Accepted: 01/17/2017] [Indexed: 11/21/2022]
Abstract
The ability of cobalamin to coordinate different upper axial ligands gives rise to a diversity of reactivity. Traditionally, adenosylcobalamin is associated with radical-based rearrangements, and methylcobalamin with methyl cation transfers. Recently, however, a new role for adenosylcobalamin has been discovered as a light sensor, and a methylcobalamin-dependent enzyme has been identified that is suggested to transfer a methyl anion. Additionally, recent studies have provided a wealth of new information about a third class of cobalamin-dependent enzymes that do not appear to use an upper ligand. They function in reductive dehalogenations and epoxide reduction reactions. Finally, mechanistic details are beginning to emerge about the cobalamin-dependent S-adenosylmethionine radical enzyme superfamily for which the role of cobalamin has been largely enigmatic.
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19
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Characterization of Radical S-adenosylmethionine Enzymes and Intermediates in their Reactions by Continuous Wave and Pulse Electron Paramagnetic Resonance Spectroscopies. FUTURE DIRECTIONS IN METALLOPROTEIN AND METALLOENZYME RESEARCH 2017. [DOI: 10.1007/978-3-319-59100-1_6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
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20
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Heidinger L, Kneuttinger AC, Kashiwazaki G, Weber S, Carell T, Schleicher E. Direct observation of a deoxyadenosyl radical in an active enzyme environment. FEBS Lett 2016; 590:4489-4494. [PMID: 27878994 DOI: 10.1002/1873-3468.12498] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2016] [Revised: 11/16/2016] [Accepted: 11/17/2016] [Indexed: 11/11/2022]
Abstract
5'-deoxyadenosyl radicals have been proposed as the first common intermediate in the molecular reaction mechanism of the family of radical S-adenosyl-l-methionine (SAM) enzymes. However, this radical species has not yet been directly observed in a catalytically active enzyme environment. In a reduced and SAM-containing C140A mutant of the spore photoproduct lyase from Geobacillus thermodenitrificans, a mutant with altered catalytic activity, we were able to identify an organic radical with pronounced hyperfine structure using electron paramagnetic resonance spectroscopy. Guided by quantum-chemical computations at the density functional theory level of theory, this radical could be tentatively assigned to a deoxyadenosyl radical, which provides first experimental evidence for this intermediate in the reaction mechanism of radical SAM enzymes.
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Affiliation(s)
- Lorenz Heidinger
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Germany
| | - Andrea C Kneuttinger
- Department für Chemie, Ludwig-Maximilians-Universität München, Germany.,Institute of Biophysics and Physical Biochemistry, University of Regensburg, Germany
| | - Gengo Kashiwazaki
- Department für Chemie, Ludwig-Maximilians-Universität München, Germany
| | - Stefan Weber
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Germany
| | - Thomas Carell
- Department für Chemie, Ludwig-Maximilians-Universität München, Germany
| | - Erik Schleicher
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Germany
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21
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Horitani M, Shisler K, Broderick WE, Hutcheson RU, Duschene KS, Marts AR, Hoffman BM, Broderick JB. Radical SAM catalysis via an organometallic intermediate with an Fe-[5'-C]-deoxyadenosyl bond. Science 2016; 352:822-5. [PMID: 27174986 DOI: 10.1126/science.aaf5327] [Citation(s) in RCA: 103] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Accepted: 03/29/2016] [Indexed: 11/02/2022]
Abstract
Radical S-adenosylmethionine (SAM) enzymes use a [4Fe-4S] cluster to cleave SAM to initiate diverse radical reactions. These reactions are thought to involve the 5'-deoxyadenosyl radical intermediate, which has not yet been detected. We used rapid freeze-quenching to trap a catalytically competent intermediate in the reaction catalyzed by the radical SAM enzyme pyruvate formate-lyase activating enzyme. Characterization of the intermediate by electron paramagnetic resonance and (13)C, (57)Fe electron nuclear double-resonance spectroscopies reveals that it contains an organometallic center in which the 5' carbon of a SAM-derived deoxyadenosyl moiety forms a bond with the unique iron site of the [4Fe-4S] cluster. Discovery of this intermediate extends the list of enzymatic bioorganometallic centers to the radical SAM enzymes, the largest enzyme superfamily known, and reveals intriguing parallels to B12 radical enzymes.
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Affiliation(s)
- Masaki Horitani
- Department of Chemistry, Northwestern University, Evanston, IL 60208, USA
| | - Krista Shisler
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717, USA
| | - William E Broderick
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717, USA
| | - Rachel U Hutcheson
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717, USA
| | - Kaitlin S Duschene
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717, USA
| | - Amy R Marts
- Department of Chemistry, Northwestern University, Evanston, IL 60208, USA
| | - Brian M Hoffman
- Department of Chemistry, Northwestern University, Evanston, IL 60208, USA.
| | - Joan B Broderick
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717, USA.
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22
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Affiliation(s)
- Jennifer Bridwell-Rabb
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
| | - Catherine L Drennan
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
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23
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Horitani M, Byer AS, Shisler KA, Chandra T, Broderick JB, Hoffman BM. Why Nature Uses Radical SAM Enzymes so Widely: Electron Nuclear Double Resonance Studies of Lysine 2,3-Aminomutase Show the 5'-dAdo• "Free Radical" Is Never Free. J Am Chem Soc 2015; 137:7111-21. [PMID: 25923449 PMCID: PMC4612528 DOI: 10.1021/jacs.5b00498] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Lysine 2,3-aminomutase (LAM) is a radical S-adenosyl-L-methionine (SAM) enzyme and, like other members of this superfamily, LAM utilizes radical-generating machinery comprising SAM anchored to the unique Fe of a [4Fe-4S] cluster via a classical five-membered N,O chelate ring. Catalysis is initiated by reductive cleavage of the SAM S-C5' bond, which creates the highly reactive 5'-deoxyadenosyl radical (5'-dAdo•), the same radical generated by homolytic Co-C bond cleavage in B12 radical enzymes. The SAM surrogate S-3',4'-anhydroadenosyl-L-methionine (anSAM) can replace SAM as a cofactor in the isomerization of L-α-lysine to L-β-lysine by LAM, via the stable allylic anhydroadenosyl radical (anAdo•). Here electron nuclear double resonance (ENDOR) spectroscopy of the anAdo• radical in the presence of (13)C, (2)H, and (15)N-labeled lysine completes the picture of how the active site of LAM from Clostridium subterminale SB4 "tames" the 5'-dAdo• radical, preventing it from carrying out harmful side reactions: this "free radical" in LAM is never free. The low steric demands of the radical-generating [4Fe-4S]/SAM construct allow the substrate target to bind adjacent to the S-C5' bond, thereby enabling the 5'-dAdo• radical created by cleavage of this bond to react with its partners by undergoing small motions, ∼0.6 Å toward the target and ∼1.5 Å overall, that are controlled by tight van der Waals contact with its partners. We suggest that the accessibility to substrate and ready control of the reactive C5' radical, with "van der Waals control" of small motions throughout the catalytic cycle, is common within the radical SAM enzyme superfamily and is a major reason why these enzymes are the preferred means of initiating radical reactions in nature.
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Affiliation(s)
- Masaki Horitani
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Amanda S. Byer
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States
| | - Krista A. Shisler
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States
| | - Tilak Chandra
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States
| | - Joan B. Broderick
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States
| | - Brian M. Hoffman
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
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24
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Affiliation(s)
- Perry Allen Frey
- From the Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706
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25
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Iannazzo L, Laisné G, Fonvielle M, Braud E, Herbeuval JP, Arthur M, Etheve-Quelquejeu M. Synthesis of 3′-Fluoro-tRNA Analogues for Exploring Non-ribosomal Peptide Synthesis in Bacteria. Chembiochem 2015; 16:477-86. [DOI: 10.1002/cbic.201402523] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2014] [Indexed: 11/08/2022]
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26
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Lerner E, Orevi T, Ben Ishay E, Amir D, Haas E. Kinetics of fast changing intramolecular distance distributions obtained by combined analysis of FRET efficiency kinetics and time-resolved FRET equilibrium measurements. Biophys J 2014; 106:667-76. [PMID: 24507607 DOI: 10.1016/j.bpj.2013.11.4500] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2013] [Revised: 10/13/2013] [Accepted: 11/05/2013] [Indexed: 10/25/2022] Open
Abstract
Detailed studies of the mechanisms of macromolecular conformational transitions such as protein folding are enhanced by analysis of changes of distributions for intramolecular distances during the transitions. Time-resolved Förster resonance energy transfer (FRET) measurements yield such data, but the more readily available kinetics of mean FRET efficiency changes cannot be analyzed in terms of changes in distances because of the sixth-power dependence on the mean distance. To enhance the information obtained from mean FRET efficiency kinetics, we combined the analyses of FRET efficiency kinetics and equilibrium trFRET experiments. The joint analysis enabled determination of transient distance distributions along the folding reaction both in cases where a two-state transition is valid and in some cases consisting of a three-state scenario. The procedure and its limits were tested by simulations. Experimental data obtained from stopped-flow measurements of the refolding of Escherichia coli adenylate kinase were analyzed. The distance distributions between three double-labeled mutants, in the collapsed transient state, were determined and compared to those obtained experimentally using the double-kinetics technique. The proposed method effectively provides information on distance distributions of kinetically accessed intermediates of fast conformational transitions induced by common relaxation methods.
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Affiliation(s)
- E Lerner
- The Mina and Everard Goodman Faculty of Life Sciences, Bar Ilan University, Ramat Gan, Israel 52900
| | - T Orevi
- The Mina and Everard Goodman Faculty of Life Sciences, Bar Ilan University, Ramat Gan, Israel 52900
| | - E Ben Ishay
- The Mina and Everard Goodman Faculty of Life Sciences, Bar Ilan University, Ramat Gan, Israel 52900
| | - D Amir
- The Mina and Everard Goodman Faculty of Life Sciences, Bar Ilan University, Ramat Gan, Israel 52900
| | - E Haas
- The Mina and Everard Goodman Faculty of Life Sciences, Bar Ilan University, Ramat Gan, Israel 52900.
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27
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Stich TA, Myers WK, Britt RD. Paramagnetic intermediates generated by radical S-adenosylmethionine (SAM) enzymes. Acc Chem Res 2014; 47:2235-43. [PMID: 24991701 PMCID: PMC4139163 DOI: 10.1021/ar400235n] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
A [4Fe-4S](+) cluster reduces a bound S-adenosylmethionine (SAM) molecule, cleaving it into methionine and a 5'-deoxyadenosyl radical (5'-dA(•)). This step initiates the varied chemistry catalyzed by each of the so-called radical SAM enzymes. The strongly oxidizing 5'-dA(•) is quenched by abstracting a H-atom from a target species. In some cases, this species is an exogenous molecule of substrate, for example, L-tyrosine in the [FeFe] hydrogenase maturase, HydG. In other cases, the target is a proteinaceous residue as in all the glycyl radical forming enzymes. The generation of this initial radical species and the subsequent chemistry involving downstream radical intermediates is meticulously controlled by the enzyme so as to prevent unwanted reactions. But the manner in which this control is exerted is unknown. Electron paramagnetic resonance (EPR) spectroscopy has proven to be a valuable tool used to gain insight into these mechanisms. In this Account, we summarize efforts to trap such radical intermediates in radical SAM enzymes and highlight four examples in which EPR spectroscopic results have shed significant light on the corresponding mechanism. For lysine 2,3-aminomutase, nearly each possible intermediate, from an analogue of the initial 5'-dA(•) to the product radical L-β-lysine, has been explored. A paramagnetic intermediate observed in biotin synthase is shown to involve an auxiliary [FeS] cluster whose bridging sulfide is a co-substrate for the final step in the biosynthesis of vitamin B7. In HydG, the L-tyrosine substrate is converted in unprecedented fashion to a 4-oxidobenzyl radical on the way to generating CO and CN(-) ligands for the [FeFe] cluster of hydrogenase. And finally, EPR has confirmed a mechanistic proposal for the antibiotic resistance protein Cfr, which methylates the unactivated sp(2)-hybridized C8-carbon of an adenosine base of 23S ribosomal RNA. These four systems provide just a brief survey of the ever-growing set of radical SAM enzymes. The diverse chemistries catalyzed by these enzymes make them an intriguing target for continuing study, and EPR spectroscopy, in particular, seems ideally placed to contribute to our understanding.
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Affiliation(s)
- Troy A. Stich
- Department of Chemistry, University of California, One Shields
Avenue, Davis, California 95616, United States
| | - William K. Myers
- Department of Chemistry, University of California, One Shields
Avenue, Davis, California 95616, United States
| | - R. David Britt
- Department of Chemistry, University of California, One Shields
Avenue, Davis, California 95616, United States
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28
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Broderick JB, Duffus B, Duschene KS, Shepard EM. Radical S-adenosylmethionine enzymes. Chem Rev 2014; 114:4229-317. [PMID: 24476342 PMCID: PMC4002137 DOI: 10.1021/cr4004709] [Citation(s) in RCA: 584] [Impact Index Per Article: 58.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2013] [Indexed: 12/22/2022]
Affiliation(s)
- Joan B. Broderick
- Department of Chemistry and
Biochemistry, Montana State University, Bozeman, Montana 59717, United States
| | - Benjamin
R. Duffus
- Department of Chemistry and
Biochemistry, Montana State University, Bozeman, Montana 59717, United States
| | - Kaitlin S. Duschene
- Department of Chemistry and
Biochemistry, Montana State University, Bozeman, Montana 59717, United States
| | - Eric M. Shepard
- Department of Chemistry and
Biochemistry, Montana State University, Bozeman, Montana 59717, United States
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29
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Frey PA. Travels with carbon-centered radicals. 5'-deoxyadenosine and 5'-deoxyadenosine-5'-yl in radical enzymology. Acc Chem Res 2014; 47:540-9. [PMID: 24308628 DOI: 10.1021/ar400194k] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
As a graduate student under Professor R. H. Abeles, I began my journey with 5'-deoxyadenosine, studying the coenzyme B12 (adenosylcobalamin)-dependent dioldehydrase (DDH). I proved that suicide inactivation of dioldehydrase by glycolaldehyde proceeded with irreversible cleavage of adenosylcobalamin to 5'-deoxyadenosine. I further showed that suicide inactivation by [2-(3)H]glycolaldehyde produced 5'-deoxy[(3)H]adenosine, the first demonstration of hydrogen transfer to adenosyl-C5' of adenosylcobalamin. The tritium kinetic isotope effect (T)k was 15, which correlated well with the measurement (D)k = 12 for transformation of [1-(2)H]propane-1,2-diol to [2-(2)H]propionaldehyde by DDH. After establishing my own research program, I returned to the glycolaldehyde inactivation of DDH, showing by EPR that suicide inactivation produced glycolaldehyde-2-yl. In retrospect, suicide inactivation involved scission of adenosylcobalamin to 5'-deoxyadenosine-5'-yl, which abstracted a hydrogen from glycolaldehyde. Captodative-stabilized glycolaldehyde-2-yl could not react further, leading to suicide inactivation. In 1986, my colleagues and I took up the problem of the mechanism by which lysine 2,3-aminomutase (LAM) catalyzes S-adenosylmethionine (SAM) and pyridoxal-5'-phosphate (PLP)-dependent interconversion of l-lysine and l-β-lysine. Because the reaction followed the pattern of adenosylcobalamin-dependent rearrangements, I postulated that SAM might be an evolutionary predecessor to adenosylcobalamin. Testing this hypothesis, we traced hydrogen transfer from lysine through the adenosyl-C5' of SAM to β-lysine. Thus, the 5'-deoxyadenosyl of SAM mediated hydrogen transfer by LAM exactly as in adenosylcobalamin mediated hydrogen transfer in B12-dependent isomerizations. The mechanism postulated that SAM cleaves to form 5'-deoxyadenosine-5'-yl followed by abstraction of C3(H) from PLP-α-lysine aldimine to form PLP-α-lysine-3-yl. PLP-α-lysine-3-yl isomerizes to pyridoxal-β-lysine-2-yl, and a hydrogen abstraction from 5'-deoxyadenosine regenerates 5'-deoxyadenosine-5'-yl and releases β-lysine. Of four radicals in the postulated mechanism, three have been characterized by EPR spectroscopy as kinetically competent intermediates. The analysis of the role of iron allowed researchers to elucidate the mechanism by which SAM is cleaved to 5'-deoxyadenosine-5'-yl. LAM contains one [4Fe-4S] cluster ligated by three cysteine residues. As shown by ENDOR spectroscopy and X-ray crystallography, the fourth ligand to the cluster is SAM, through the methionyl carboxylate and amino groups. Inner sphere electron transfer within the [4Fe-4S](1+)-SAM complex leads to [4Fe-4S](2+)-Met and 5'-deoxyadenosine-5'-yl. The iron-binding motif in LAM, CxxxCxxC, found by other groups in four other SAM-dependent enzymes, is the founding motif for the radical SAM superfamily. These enzymes number in the tens of thousands and are responsible for highly diverse and chemically difficult transformations in the biosphere. Available information supports the hypothesis that this superfamily provides the chemical context from which the much more structurally complex adenosylcobalamin evolved.
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Affiliation(s)
- Perry A. Frey
- University of Wisconsin—Madison, 1710 University Avenue, Madison, Wisconsin 53726, United States
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30
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Buckel W, Friedrich P, Golding BT. Wasserstoffbrücken führen das kurzlebige 5′-Desoxyadenosylradikal zum Tatort. Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201205299] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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31
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Hutcheson RU, Broderick JB. Radical SAM enzymes in methylation and methylthiolation. Metallomics 2012; 4:1149-54. [PMID: 22992596 DOI: 10.1039/c2mt20136d] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Radical S-adenosyl-l-methionine (SAM) enzymes are a large and diverse superfamily with functions ranging from enzyme activation through a single H atom abstraction to complex organic and metal cofactor synthesis involving a series of steps. Though these enzymes carry out a variety of functions, they share common structural and mechanistic characteristics. All of them contain a site-differentiated [4Fe-4S] cluster, ligated by a CX(3)CX(2)C or similar motif, which binds SAM at the unique iron. The [4Fe-4S](1+) state of the cluster reductively cleaves SAM to produce a 5'-deoxyadenosyl radical, which serves to initiate the diverse reactions catalyzed by these enzymes. Recent highlights in the understanding of radical SAM enzymes will be presented, with a particular emphasis on enzymes catalyzing methylation and methythiolation reactions.
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Affiliation(s)
- Rachel U Hutcheson
- Department of Chemistry and Biochemistry and the Astrobiology Biogeocatalysis Research Center, Montana State University, Bozeman, MT 59717, USA
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Buckel W, Friedrich P, Golding BT. Hydrogen bonds guide the short-lived 5'-deoxyadenosyl radical to the place of action. Angew Chem Int Ed Engl 2012; 51:9974-6. [PMID: 22945861 DOI: 10.1002/anie.201205299] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2012] [Indexed: 11/08/2022]
Affiliation(s)
- Wolfgang Buckel
- Laboratorium für Mikrobiologie, Fachbereich Biologie, Philipps-Universität, 35032 Marburg, Germany.
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Bandarian V. Radical SAM enzymes involved in the biosynthesis of purine-based natural products. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2012; 1824:1245-53. [PMID: 22902275 DOI: 10.1016/j.bbapap.2012.07.014] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2011] [Revised: 07/21/2012] [Accepted: 07/26/2012] [Indexed: 12/19/2022]
Abstract
The radical S-adenosyl-l-methionine (SAM) superfamily is a widely distributed group of iron-sulfur containing proteins that exploit the reactivity of the high energy intermediate, 5'-deoxyadenosyl radical, which is produced by the reductive cleavage of SAM, to carry-out complex radical-mediated transformations. The reactions catalyzed by radical SAM enzymes range from simple group migrations to complex reactions in protein and RNA modification. This review will highlight three radical SAM enzymes that catalyze reactions involving modified guanosines in the biosynthesis pathways of the hypermodified tRNA base wybutosine; secondary metabolites of 7-deazapurine structure, including the hypermodified tRNA base queuosine; and the redox cofactor F(420). This article is part of a Special Issue entitled: Radical SAM enzymes and Radical Enzymology.
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Affiliation(s)
- Vahe Bandarian
- University of Arizona, Department of Chemistry and Biochemistry, 1041 E. Lowell St., Tucson, AZ 85721‐0088, USA.
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Conrad KS, Brunold TC. Spectroscopic and computational studies of glutathionylcobalamin: nature of Co-S bonding and comparison to Co-C bonding in coenzyme B12. Inorg Chem 2011; 50:8755-66. [PMID: 21859072 DOI: 10.1021/ic200428r] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Glutathionylcobalamin (GSCbl) is a unique, biologically relevant cobalamin featuring an axial Co-S bond that distinguishes it from the enzymatically active forms of vitamin B(12), which possess axial Co-C bonds. GSCbl has been proposed to serve as an intermediate in cobalamin processing and, more recently, as a therapeutic for neurological disorders associated with oxidative stress. In this study, GSCbl and its close relative cysteinylcobalamin (CysCbl) were investigated using electronic absorption, circular dichroism, magnetic circular dichroism, and resonance Raman spectroscopies. The spectroscopic data were analyzed in the framework of density functional theory (DFT) and time-dependent DFT computations to generate experimentally validated electronic structure descriptions. Although the change in the upper axial ligand from an alkyl to a thiol group represents a major perturbation in terms of the size, basicity, and polarizability of the coordinating atom, our spectroscopic and computational results reveal striking similarities in electronic structure between methylcobalamin (MeCbl) and GSCbl, especially with regard to the σ donation from the alkyl/thiol ligand and the extent of mixing between the cobalt 3d and the ligand frontier orbitals. A detailed comparison of Co-C and Co-S bonding in MeCbl and GSCbl, respectively, is presented, and the implications of our results with respect to the proposed biological roles of GSCbl are discussed.
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Affiliation(s)
- Karen S Conrad
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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Challand MR, Driesener RC, Roach PL. Radical S-adenosylmethionine enzymes: mechanism, control and function. Nat Prod Rep 2011; 28:1696-721. [PMID: 21779595 DOI: 10.1039/c1np00036e] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Martin R Challand
- School of Cellular and Molecular Medicine, Medical Sciences Building, University of Bristol, University Walk, Bristol BS81TD, USA
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Vey JL, Drennan CL. Structural insights into radical generation by the radical SAM superfamily. Chem Rev 2011; 111:2487-506. [PMID: 21370834 PMCID: PMC5930932 DOI: 10.1021/cr9002616] [Citation(s) in RCA: 183] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Jessica L Vey
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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Wu B, Szymański W, Heberling MM, Feringa BL, Janssen DB. Aminomutases: mechanistic diversity, biotechnological applications and future perspectives. Trends Biotechnol 2011; 29:352-62. [PMID: 21477876 DOI: 10.1016/j.tibtech.2011.02.005] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2011] [Revised: 02/22/2011] [Accepted: 02/23/2011] [Indexed: 11/26/2022]
Abstract
Aminomutases carry out the chemically challenging exchange of a hydrogen atom and an amine substituent present on neighboring carbon atoms. In recent years, aminomutases have been intensively investigated for their biophysical, structural and mechanistic characteristics. The reactions catalyzed by these enzymes have considerable potential for biotechnological applications. Here, we present an overview of this diverse group of enzymes, with a focus on enzymatic mechanisms and recent developments in their use in applied biocatalysis.
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Affiliation(s)
- Bian Wu
- Department of Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
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Frey PA, Reed GH. Pyridoxal-5'-phosphate as the catalyst for radical isomerization in reactions of PLP-dependent aminomutases. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2011; 1814:1548-57. [PMID: 21435400 DOI: 10.1016/j.bbapap.2011.03.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2010] [Revised: 03/08/2011] [Accepted: 03/09/2011] [Indexed: 10/18/2022]
Abstract
PLP catalyzes the 1,2 shifts of amino groups in free radical-intermediates at the active sites of amino acid aminomutases. Free radical forms of the substrates are created upon H atom abstractions carried out by the 5'-deoxyadenosyl radical. In most of these enzymes, the 5'-deoxyadenosyl radical is generated by an iron-sulfur cluster-mediated reductive cleavage of S-adenosyl-(S)-methionine. However, in lysine 5,6-aminomutase and ornithine 4,5-aminomutase, the radical is generated by homolytic cleavage of the cobalt-carbon bond of adenosylcobalamin. The imine linkages in the initial radical forms of the external aldimines undergo radical addition to form azacyclopropylcarbinyl radicals as central intermediates in the catalytic cycles. In the case of lysine 2,3-aminomutase, the multistep catalytic mechanism is corroborated by direct spectroscopic observation and characterization of a product radical trapped during steady-state turnover. Analogues of the substrate-related radical having substituents adjacent to the radical center to stabilize the unpaired electron are also observed and characterized spectroscopically. A functional allylic analogue of the 5'-deoxyadenosyl radical is observed spectroscopically. A high-resolution crystal structure fully supports the mechanistic proposals. Evidence for a similar free radical mediated amino group transfer in the adenosylcobalamin-dependent lysine 5,6-aminomutase is provided by spectroscopic detection and characterization of radicals generated from the 4-thia analogues of the lysine substrates. This article is part of a Special Issue entitled: Pyridoxal Phospate Enzymology.
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Affiliation(s)
- Perry A Frey
- Department of Biochemistry, University of Wisconsin-Madison, 1710 University Avenue, Madison, WI 53726, USA.
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Ruzicka FJ, Frey PA. Kinetic and spectroscopic evidence of negative cooperativity in the action of lysine 2,3-aminomutase. J Phys Chem B 2010; 114:16118-24. [PMID: 20608698 DOI: 10.1021/jp103856m] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Lysine 2,3-aminomutase (LAM) catalyzes the interconversion of L-lysine and L-β-lysine, a component of a number of antibiotics. The reaction requires the cofactors S-adenosyl-L-methionine (SAM), pyridoxal-5'-phosphate (PLP), and a [4Fe-4S] cluster. LAM is a founding member of the radical SAM superfamily of enzymes. LAM is highly specific for L-lysine and will not accept most other amino acids as substrates. L-alanine and L-2-aminobutyrate at 0.2 M react as substrates for LAM at, respectively, 5 × 10(-6) and 8 × 10(-5) times the rate with saturating L-lysine. Saturating ethylamine accelerates the L-alanine reaction 70-fold, and saturating methylamine accelerates the L-2-aminobutyrate reaction 47-fold. The primary amines binding at the active site of LAM with L-alanine or L-2-aminobutyrate simulate L-lysine. The steady-state kinetics of the reaction of L-alanine + ethylamine displays negative cooperativity with respect to L-alanine. The second-order rate constant for production of β-alanine in the reaction of L-alanine and saturating ethylamine is 0.040 M(-1) s(-1), which is 2 × 10(-5) times the value of k(cat)/K(m) for the reaction of L-lysine. When L-lysine is at a concentration 1/16th of K(m), the lysyl-free radical intermediate is hardly detectable by EPR; however, the addition of L-alanine at high concentration (0.2 M) enhances free radical formation, and the addition of ethylamine further enhances radical formation. These facts complement the kinetic observations and support negative cooperativity in the reaction of L-alanine as a substrate for LAM. Present results and independent evidence support negative cooperativity in the reaction of L-lysine as well.
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Affiliation(s)
- Frank J Ruzicka
- Department of Biochemistry, University of Wisconsin-Madison, 1710 University Avenue, Madison, Wisconsin 53726, USA
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40
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Ruszczycky MW, Choi SH, Liu HW. Stoichiometry of the redox neutral deamination and oxidative dehydrogenation reactions catalyzed by the radical SAM enzyme DesII. J Am Chem Soc 2010; 132:2359-69. [PMID: 20121093 DOI: 10.1021/ja909451a] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
DesII from Streptomyces venezuelae is a radical SAM (S-adenosyl-l-methionine) enzyme that catalyzes the deamination of TDP-4-amino-4,6-dideoxy-d-glucose to form TDP-3-keto-4,6-dideoxy-d-glucose in the biosynthesis of TDP-d-desosamine. DesII also catalyzes the dehydrogenation of the nonphysiological substrate TDP-D-quinovose to TDP-3-keto-6-deoxy-d-glucose. These properties prompted an investigation of how DesII handles SAM in the redox neutral deamination versus the oxidative dehydrogenation reactions. This work was facilitated by the development of an enzymatic synthesis of TDP-4-amino-4,6-dideoxy-d-glucose that couples a transamination equilibrium to the thermodynamically favorable oxidation of formate. In this study, DesII is found to consume SAM versus TDP-sugar with stoichiometries of 0.96 +/- 0.05 and 1.01 +/- 0.05 in the deamination and dehydrogenation reactions, respectively, using Na(2)S(2)O(4) as the reductant. Importantly, no significant change in stoichiometry is observed when the flavodoxin/flavodoxin NADP(+) oxidoreductase/NADPH reducing system is used in place of Na(2)S(2)O(4). Moreover, there is no evidence of an uncoupled or abortive process in the deamination reaction, as indicated by the observation that dehydrogenation can take place in the absence of an external source of reductant whereas deamination cannot. Mechanistic and biochemical implications of these results are discussed.
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Affiliation(s)
- Mark W Ruszczycky
- Division of Medicinal Chemistry, College of Pharmacy, and Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas 78712, USA
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41
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Brindley AA, Zajicek R, Warren MJ, Ferguson SJ, Rigby SE. NirJ, a radical SAM family member of thed1heme biogenesis cluster. FEBS Lett 2010; 584:2461-6. [DOI: 10.1016/j.febslet.2010.04.053] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2009] [Revised: 04/16/2010] [Accepted: 04/19/2010] [Indexed: 11/28/2022]
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42
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Maity AN, Hsieh CP, Huang MH, Chen YH, Tang KH, Behshad E, Frey PA, Ke SC. Evidence for Conformational Movement and Radical Mechanism in the Reaction of 4-Thia-l-lysine with Lysine 5,6-Aminomutase. J Phys Chem B 2009; 113:12161-3. [DOI: 10.1021/jp905357a] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Amarendra N. Maity
- Physics Department, National Dong Hwa University, Hualien, Taiwan 974-01, Department of Biochemistry, University of Wisconsin—Madison, Madison, Wisconsin 53726
| | - Chih-Pin Hsieh
- Physics Department, National Dong Hwa University, Hualien, Taiwan 974-01, Department of Biochemistry, University of Wisconsin—Madison, Madison, Wisconsin 53726
| | - Ming-Hui Huang
- Physics Department, National Dong Hwa University, Hualien, Taiwan 974-01, Department of Biochemistry, University of Wisconsin—Madison, Madison, Wisconsin 53726
| | - Yung-Han Chen
- Physics Department, National Dong Hwa University, Hualien, Taiwan 974-01, Department of Biochemistry, University of Wisconsin—Madison, Madison, Wisconsin 53726
| | - Kuo-Hsiang Tang
- Physics Department, National Dong Hwa University, Hualien, Taiwan 974-01, Department of Biochemistry, University of Wisconsin—Madison, Madison, Wisconsin 53726
| | - Elham Behshad
- Physics Department, National Dong Hwa University, Hualien, Taiwan 974-01, Department of Biochemistry, University of Wisconsin—Madison, Madison, Wisconsin 53726
| | - Perry A. Frey
- Physics Department, National Dong Hwa University, Hualien, Taiwan 974-01, Department of Biochemistry, University of Wisconsin—Madison, Madison, Wisconsin 53726
| | - Shyue-Chu Ke
- Physics Department, National Dong Hwa University, Hualien, Taiwan 974-01, Department of Biochemistry, University of Wisconsin—Madison, Madison, Wisconsin 53726
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43
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Product inhibition in the radical S-adenosylmethionine family. FEBS Lett 2009; 583:1358-62. [PMID: 19328201 DOI: 10.1016/j.febslet.2009.03.044] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2009] [Revised: 03/20/2009] [Accepted: 03/22/2009] [Indexed: 11/22/2022]
Abstract
Members of the radical S-adenosylmethionine (AdoMet) superfamily reductively cleave AdoMet to generate the highly reactive 5'-deoxyadenosyl radical (DOA()) which initiates biological transformations by abstraction of a hydrogen atom. We demonstrate that three members of the family: biotin synthase (BioB), lipoyl synthase (LipA) and tyrosine lyase (ThiH) are inhibited in vitro by a combination of the products 5'-deoxyadenosine (DOA) and methionine. These results suggest the observed inhibition is a common feature of the radical AdoMet proteins that form DOA and methionine as products. Addition of 5'-methylthioadenosine/S-adenosylhomocysteine nucleosidase (MTAN) to BioB, LipA or ThiH activity assays removed the product inhibition by catalysing the hydrolysis of DOA and gave an increase in activity.
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44
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Control of radical chemistry in the AdoMet radical enzymes. Curr Opin Chem Biol 2009; 13:74-83. [PMID: 19269883 DOI: 10.1016/j.cbpa.2009.01.022] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2008] [Accepted: 01/30/2009] [Indexed: 11/20/2022]
Abstract
The radical AdoMet superfamily comprises a diverse set of >2800 enzymes that utilize iron-sulfur clusters and S-adenosylmethionine (SAM or AdoMet) to initiate a diverse set of radical-mediated reactions. The intricate control these enzymes exercise over the radical transformations they catalyze is an amazing feat of elegance and sophistication in biochemistry. This review focuses on the accumulating evidence for how these enzymes control this remarkable chemistry, including controlling the reactivity between the iron-sulfur cluster and AdoMet, and controlling the subsequent radical transformations.
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45
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Pierik AJ, Graf T, Pemberton L, Golding BT, Rétey J. But-3-ene-1,2-diol: A Mechanism-Based Active Site Inhibitor for Coenzyme B12-Dependent Glycerol Dehydratase. Chembiochem 2008; 9:2268-75. [DOI: 10.1002/cbic.200800213] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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46
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Yokoyama K, Ohmori D, Kudo F, Eguchi T. Mechanistic Study on the Reaction of a Radical SAM Dehydrogenase BtrN by Electron Paramagnetic Resonance Spectroscopy. Biochemistry 2008; 47:8950-60. [DOI: 10.1021/bi800509x] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Kenichi Yokoyama
- Department of Chemistry and Department of Chemistry and Materials Science, Tokyo Institute of Technology, O-okayama, Meguro-ku, Tokyo 152-8551, Japan, and Department of Chemistry, Juntendo University, Inba, Chiba 270-1695, Japan
| | - Daijiro Ohmori
- Department of Chemistry and Department of Chemistry and Materials Science, Tokyo Institute of Technology, O-okayama, Meguro-ku, Tokyo 152-8551, Japan, and Department of Chemistry, Juntendo University, Inba, Chiba 270-1695, Japan
| | - Fumitaka Kudo
- Department of Chemistry and Department of Chemistry and Materials Science, Tokyo Institute of Technology, O-okayama, Meguro-ku, Tokyo 152-8551, Japan, and Department of Chemistry, Juntendo University, Inba, Chiba 270-1695, Japan
| | - Tadashi Eguchi
- Department of Chemistry and Department of Chemistry and Materials Science, Tokyo Institute of Technology, O-okayama, Meguro-ku, Tokyo 152-8551, Japan, and Department of Chemistry, Juntendo University, Inba, Chiba 270-1695, Japan
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Kim J, Darley DJ, Buckel W, Pierik AJ. An allylic ketyl radical intermediate in clostridial amino-acid fermentation. Nature 2008; 452:239-42. [PMID: 18337824 DOI: 10.1038/nature06637] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2007] [Accepted: 01/10/2008] [Indexed: 11/09/2022]
Abstract
The human pathogenic bacterium Clostridium difficile thrives by the fermentation of l-leucine to ammonia, CO(2), 3-methylbutanoate and 4-methylpentanoate under anaerobic conditions. The reductive branch to 4-methylpentanoate proceeds by means of the dehydration of (R)-2-hydroxy-4-methylpentanoyl-CoA to 4-methylpent-2-enoyl-CoA, which is chemically the most demanding step. Ketyl radicals have been proposed to mediate this reaction catalysed by an iron-sulphur-cluster-containing dehydratase, which requires activation by ATP-dependent electron transfer from a second iron-sulphur protein functionally similar to the iron protein of nitrogenase. Here we identify a kinetically competent product-related allylic ketyl radical bound to the enzyme by electron paramagnetic resonance spectroscopy employing isotope-labelled (R)-2-hydroxy-4-methylpentanoyl-CoA species. We also found that the enzyme generated the stabilized pentadienoyl ketyl radical from the substrate analogue 2-hydroxypent-4-enoyl-CoA, supporting the proposed mechanism. Our results imply that also other 2-hydroxyacyl-CoA dehydratases and the related benzoyl-CoA reductases-present in anaerobically living bacteria-employ ketyl radical intermediates. The absence of radical generators such as coenzyme B12, S-adenosylmethionine or oxygen makes these enzymes unprecedented in biochemistry.
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Affiliation(s)
- Jihoe Kim
- Laboratorium für Mikrobiologie, Fachbereich Biologie, Philipps-Universität, D35032 Marburg, Germany
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48
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Abstract
The radical S-adenosylmethionine (SAM) superfamily currently comprises more than 2800 proteins with the amino acid sequence motif CxxxCxxC unaccompanied by a fourth conserved cysteine. The charcteristic three-cysteine motif nucleates a [4Fe-4S] cluster, which binds SAM as a ligand to the unique Fe not ligated to a cysteine residue. The members participate in more than 40 distinct biochemical transformations, and most members have not been biochemically characterized. A handful of the members of this superfamily have been purified and at least partially characterized. Significant mechanistic and structural information is available for lysine 2,3-aminomutase, pyruvate formate-lyase, coproporphyrinogen III oxidase, and MoaA required for molybdopterin biosynthesis. Biochemical information is available for spore photoproduct lyase, anaerobic ribonucleotide reductase activation subunit, lipoyl synthase, and MiaB involved in methylthiolation of isopentenyladenine-37 in tRNA. The radical SAM enzymes biochemically characterized to date have in common the cleavage of the [4Fe-4S](1 +) -SAM complex to [4Fe-4S](2 +)-Met and the 5' -deoxyadenosyl radical, which abstracts a hydrogen atom from the substrate to initiate a radical mechanism.
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Affiliation(s)
- Perry A Frey
- Department of Biochemistry, University of Madison, Wisconin-Madison, Wisconsin 53726, USA.
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49
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Wang SC, Frey PA. Binding energy in the one-electron reductive cleavage of S-adenosylmethionine in lysine 2,3-aminomutase, a radical SAM enzyme. Biochemistry 2007; 46:12889-95. [PMID: 17944492 DOI: 10.1021/bi701745h] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The common step in the actions of members of the radical SAM superfamily of enzymes is the one-electron reductive cleavage of S-adenosyl-l-methionine (SAM) into methionine and the 5'-deoxyadenosyl radical. The source of the electron is the [4Fe-4S]1+ cluster characterizing the radical SAM superfamily, to which SAM is directly ligated through its methionyl carboxylate and amino groups. The energetics of the reductive cleavage of SAM is an outstanding question in the actions of radical SAM enzymes. The energetics is here reported for the action of lysine 2,3-aminomutase (LAM), which catalyzes the interconversion of l-lysine and l-beta-lysine. From earlier work, the reduction potential of the [4Fe-4S]2+/1+ cluster in LAM is -0.43 V with SAM bound to the cluster (Hinckley, G. T., and Frey, P. A. (2006) Biochemistry 45, 3219-3225), 1.4 V higher than the reported value for trialkylsulfonium ions in solution. The midpoint reduction potential upon binding l-lysine has been estimated to be -0.6 V from the values of midpoint potentials measured with SAM bound to the cluster and l-alanine in place of l-lysine, with S-adenosyl-l-homocysteine (SAH) bound to the cluster in the presence of l-lysine, and with SAH bound to the cluster in the presence of l-alanine or of l-alanine and ethylamine in place of l-lysine. The reduction potential for SAM has been estimated to be -0.99 V from the measured value for S-3',4'-anhydroadenosyl-l-methionine. The reduction potential for the [4Fe-4S] cluster is lowered 0.17 V by the binding of lysine to LAM, and the binding of SAM to the [4Fe-4S] cluster in LAM elevates its reduction potential by 0.81 V. Thus, the binding of l-lysine to LAM contributes 4 kcal mol-1, and the binding of SAM to the [4Fe-4S] cluster in LAM contributes 19 kcal mol-1 toward lowering the barrier for reductive cleavage of SAM from 32 kcal mol-1 in solution to 9 kcal mol-1 at the active site of LAM.
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Affiliation(s)
- Susan C Wang
- Department of Biochemistry, University of Wisconsin-Madison, 1710 University Avenue, Madison, Wisconsin 53726, USA
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50
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McGinley CM, Jacquot C, van der Donk WA. Synthesis of 7-thiaarachidonic acid as a mechanistic probe of prostaglandin H synthase-2. Bioorg Med Chem Lett 2007; 17:4049-52. [PMID: 17485208 PMCID: PMC2040112 DOI: 10.1016/j.bmcl.2007.04.073] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2007] [Revised: 04/20/2007] [Accepted: 04/23/2007] [Indexed: 11/16/2022]
Abstract
The mechanism by which prostaglandin synthase converts arachidonic acid to prostaglandin G(2), creating five new chiral centers in the process, is still incompletely understood. The first radical intermediate has been characterized by EPR spectroscopy but subsequent proposed intermediates have not succumbed to detection. We report the synthesis of 7-thiaarachidonic acid designed to stabilize one of the proposed radical intermediates, which may allow its detection.
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Affiliation(s)
- Chris M McGinley
- Roger Adams Laboratory, Department of Chemistry, University of Illinois, 600 S. Mathews Avenue, Urbana, IL 61801, USA
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