1
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Benjdia A, Berteau O. B 12-dependent radical SAM enzymes: Ever expanding structural and mechanistic diversity. Curr Opin Struct Biol 2023; 83:102725. [PMID: 37931378 DOI: 10.1016/j.sbi.2023.102725] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Revised: 09/26/2023] [Accepted: 10/03/2023] [Indexed: 11/08/2023]
Abstract
In the last decade, B12-dependent radical SAM enzymes have emerged as central biocatalysts in the biosynthesis of a myriad of natural products. Notably, these enzymes have been shown to catalyze carbon-carbon bond formation on unactivated carbon atoms leading to unusual methylations. Recently, structural studies have revealed unprecedented insights into the complex chemistry catalyzed by these enzymes. In this review, we cover recent advances in our understanding of B12-dependent radical SAM enzymes from a mechanistic and structural perspective. We discuss the unanticipated diversity of these enzymes which suggests evolutionary links between various biosynthetic and metabolic pathways from antibiotic to RiPP and methane biosynthesis.
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Affiliation(s)
- Alhosna Benjdia
- Université Paris-Saclay, INRAE, AgroParisTech, Micalis Institute, ChemSyBio, 78350, Jouy-en-Josas, France.
| | - Olivier Berteau
- Université Paris-Saclay, INRAE, AgroParisTech, Micalis Institute, ChemSyBio, 78350, Jouy-en-Josas, France.
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2
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Lee YH, Yeh YC, Fan PH, Zhong A, Ruszczycky MW, Liu HW. Changing Fates of the Substrate Radicals Generated in the Active Sites of the B 12-Dependent Radical SAM Enzymes OxsB and AlsB. J Am Chem Soc 2023; 145:3656-3664. [PMID: 36719327 PMCID: PMC9940012 DOI: 10.1021/jacs.2c12953] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
OxsB is a B12-dependent radical SAM enzyme that catalyzes the oxidative ring contraction of 2'-deoxyadenosine 5'-phosphate to the dehydrogenated, oxetane containing precursor of oxetanocin A phosphate. AlsB is a homologue of OxsB that participates in a similar reaction during the biosynthesis of albucidin. Herein, OxsB and AlsB are shown to also catalyze radical mediated, stereoselective C2'-methylation of 2'-deoxyadenosine monophosphate. This reaction proceeds with inversion of configuration such that the resulting product also possesses a C2' hydrogen atom available for abstraction. However, in contrast to methylation, subsequent rounds of catalysis result in C-C dehydrogenation of the newly added methyl group to yield a 2'-methylidene followed by radical addition of a 5'-deoxyadenosyl moiety to produce a heterodimer. These observations expand the scope of reactions catalyzed by B12-dependent radical SAM enzymes and emphasize the susceptibility of radical intermediates to bifurcation along different reaction pathways even within the highly organized active site of an enzyme.
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Affiliation(s)
- Yu-Hsuan Lee
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
| | - Yu-Cheng Yeh
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
| | - Po-Hsun Fan
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
| | - Aoshu Zhong
- Division of Chemical Biology & Medicinal Chemistry, College of Pharmacy, 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
| | - 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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3
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Ju KS, Nair SK. Convergent and divergent biosynthetic strategies towards phosphonic acid natural products. Curr Opin Chem Biol 2022; 71:102214. [PMID: 36202046 PMCID: PMC9722595 DOI: 10.1016/j.cbpa.2022.102214] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2022] [Revised: 08/31/2022] [Accepted: 09/05/2022] [Indexed: 01/27/2023]
Abstract
The phosphonate class of natural products have received significant interests in the post-genomic era due to the relative ease with which their biosynthetic genes may be identified and the resultant final products be characterized. Recent large-scale studies of the elucidation and distributions of phosphonate pathways have provided a robust landscape for deciphering the underlying biosynthetic logic. A recurrent theme in phosphonate biosynthetic pathways is the interweaving of enzymatic reactions across different routes, which enables diversification to elaborate chemically novel scaffolds. Here, we provide a few vignettes of how Nature has utilized both convergent and divergent biosynthetic strategies to compile pathways for production of novel phosphonates. These examples illustrate how common intermediates may either be generated or intercepted to diversify chemical scaffolds and provides a starting point for both biotechnological and synthetic biological applications towards new phosphonates by similar combinatorial approaches.
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Affiliation(s)
- Kou-San Ju
- Department of Microbiology, The Ohio State University, Columbus OH 43210,Division of Medicinal Chemistry and Pharmacognosy, The Ohio State University, Columbus OH 43210,Infectious Diseases Institute. The Ohio State University, Columbus OH 43210,Corresponding authors: Kou-San Ju () and Satish K. Nair ()
| | - Satish K. Nair
- Department of Biochemistry, University of Illinois, Urbana, IL 61801,Center for Biophysics and Quantitative Biology, University of Illinois, Urbana, IL 61801,Carl Woese Institute for Genomic Biology. University of Illinois, Urbana, IL 61801,Corresponding authors: Kou-San Ju () and Satish K. Nair ()
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4
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Cobalamin Riboswitches Are Broadly Sensitive to Corrinoid Cofactors to Enable an Efficient Gene Regulatory Strategy. mBio 2022; 13:e0112122. [PMID: 35993747 PMCID: PMC9600662 DOI: 10.1128/mbio.01121-22] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
In bacteria, many essential metabolic processes are controlled by riboswitches, gene regulatory RNAs that directly bind and detect metabolites. Highly specific effector binding enables riboswitches to respond to a single biologically relevant metabolite. Cobalamin riboswitches are a potential exception because over a dozen chemically similar but functionally distinct cobalamin variants (corrinoid cofactors) exist in nature. Here, we measured cobalamin riboswitch activity in vivo using a Bacillus subtilis fluorescent reporter system and found, among 38 tested riboswitches, a subset responded to corrinoids promiscuously, while others were semiselective. Analyses of chimeric riboswitches and structural models indicate, unlike other riboswitch classes, cobalamin riboswitches indirectly differentiate among corrinoids by sensing differences in their structural conformation. This regulatory strategy aligns riboswitch-corrinoid specificity with cellular corrinoid requirements in a B. subtilis model. Thus, bacteria can employ broadly sensitive riboswitches to cope with the chemical diversity of essential metabolites. IMPORTANCE Some bacterial mRNAs contain a region called a riboswitch which controls gene expression by binding to a metabolite in the cell. Typically, riboswitches sense and respond to a limited range of cellular metabolites, often just one type. In this work, we found the cobalamin (vitamin B12) riboswitch class is an exception, capable of sensing and responding to multiple variants of B12-collectively called corrinoids. We found cobalamin riboswitches vary in corrinoid specificity with some riboswitches responding to each of the corrinoids we tested, while others responding only to a subset of corrinoids. Our results suggest the latter class of riboswitches sense intrinsic conformational differences among corrinoids in order to support the corrinoid-specific needs of the cell. These findings provide insight into how bacteria sense and respond to an exceptionally diverse, often essential set of enzyme cofactors.
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5
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Bridwell-Rabb J, Li B, Drennan CL. Cobalamin-Dependent Radical S-Adenosylmethionine Enzymes: Capitalizing on Old Motifs for New Functions. ACS BIO & MED CHEM AU 2022; 2:173-186. [PMID: 35726326 PMCID: PMC9204698 DOI: 10.1021/acsbiomedchemau.1c00051] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Revised: 01/08/2022] [Accepted: 01/10/2022] [Indexed: 01/21/2023]
Abstract
The members of the radical S-adenosylmethionine (SAM) enzyme superfamily are responsible for catalyzing a diverse set of reactions in a multitude of biosynthetic pathways. Many members of this superfamily accomplish their transformations using the catalytic power of a 5'-deoxyadenosyl radical (5'-dAdo•), but there are also enzymes within this superfamily that bind auxiliary cofactors and extend the catalytic repertoire of SAM. In particular, the cobalamin (Cbl)-dependent class synergistically uses Cbl to facilitate challenging methylation and radical rearrangement reactions. Despite identification of this class by Sofia et al. 20 years ago, the low sequence identity between members has led to difficulty in predicting function of uncharacterized members, pinpointing catalytic residues, and elucidating reaction mechanisms. Here, we capitalize on the three recent structures of Cbl-dependent radical SAM enzymes that use common cofactors to facilitate ring contraction as well as radical-based and non-radical-based methylation reactions. With these three structures as a framework, we describe how the Cbl-dependent radical SAM enzymes repurpose the traditional SAM- and Cbl-binding motifs to form an active site where both Cbl and SAM can participate in catalysis. In addition, we describe how, in some cases, the classic SAM- and Cbl-binding motifs support the diverse functionality of this enzyme class, and finally, we define new motifs that are characteristic of Cbl-dependent radical SAM enzymes.
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Affiliation(s)
- Jennifer Bridwell-Rabb
- Department
of Chemistry, University of Michigan, 930 N University Avenue, Ann Arbor, Michigan 48109, United States,
| | - Bin Li
- Department
of Chemistry, University of Michigan, 930 N University Avenue, Ann Arbor, Michigan 48109, United States
| | - Catherine L. Drennan
- Department
of Chemistry, Massachusetts Institute of
Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States,Department
of Biology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States,Howard
Hughes Medical Institute, Massachusetts
Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
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6
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Characterization of the cobalamin-dependent radical S-adenosyl-l-methionine enzyme C-methyltransferase Fom3 in fosfomycin biosynthesis. Methods Enzymol 2022; 669:45-70. [PMID: 35644180 DOI: 10.1016/bs.mie.2021.11.025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Fosfomycin is a clinically used broad-spectrum antibiotic that has the structure of an oxirane ring with a phosphonic acid substituent and a methyl substituent. In nature, fosfomycin is produced by Streptomyces spp. and Pseudomonas sp., but biosynthesis of fosfomycin significantly differs between the two bacteria, especially in the incorporation mechanism of the methyl group. It has been proposed that the cobalamin-dependent radical S-adenosyl-l-methionine (SAM) enzyme Fom3 is responsible for the methyl-transfer reaction in Streptomyces fosfomycin biosynthesis. In this chapter, we describe the experimental methods to characterize Fom3. We performed the methylation reaction with the purified recombinant Fom3, revealing that Fom3 recognizes a cytidylylated 2-hydroxyethylphosphonate as a substrate and catalyzes stereoselective methylation of the sp3 carbon at the C2 position to afford cytidylylated (S)-2-hydroxypropylphosphonate. Reaction analysis using deuterium-labeled substrates showed that the 5'-deoxyadenosyl radical generated by reductive cleavage of SAM stereoselectively abstracts the pro-R hydrogen atom of the CH bond at the C2 position of cytidylylated 2-hydroxyethylphosphonate. Therefore, the C-methylation reaction catalyzed by Fom3 proceeds with inversion of the configuration at the C2 position. Experimental methods to elucidate the chemical structures of the substrate and products and the stereochemical course in the Fom3-catalyzed reaction could give information to progress investigation of cobalamin-dependent radical SAM C-methyltransferases.
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7
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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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8
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Sinner E, Marous DR, Townsend CA. Evolution of Methods for the Study of Cobalamin-Dependent Radical SAM Enzymes. ACS BIO & MED CHEM AU 2022; 2:4-10. [PMID: 35341020 PMCID: PMC8950095 DOI: 10.1021/acsbiomedchemau.1c00032] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
While bioinformatic evidence of cobalamin-dependent radical S-adenosylmethionine (SAM) enzymes has existed since the naming of the radical SAM superfamily in 2001, none were biochemically characterized until 2011. In the past decade, the field has flourished as methodological advances have facilitated study of the subfamily. Because of the ingenuity and perseverance of researchers in this field, we now have functional, mechanistic, and structural insight into how this class of enzymes harnesses the power of both the cobalamin and radical SAM cofactors to achieve catalysis. All of the early characterized enzymes in this subfamily were methylases, but the activity of these enzymes has recently been expanded beyond methylation. We anticipate that the characterized functions of these enzymes will become both better understood and increasingly diverse with continued study.
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Affiliation(s)
- Erica
K. Sinner
- Department
of Chemistry, Johns Hopkins University, 3400 N Charles St., Baltimore, Maryland 21218, United States
| | - Daniel R. Marous
- Department
of Chemistry, Wittenberg University, 200 W Ward St., Springfield, Ohio 45504, United States
| | - Craig A. Townsend
- Department
of Chemistry, Johns Hopkins University, 3400 N Charles St., Baltimore, Maryland 21218, United States
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9
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Lee YH, Liu HW. Studies of GenK and OxsB, two B 12-dependent radical SAM enzymes involved in natural product biosynthesis. Methods Enzymol 2022; 669:71-90. [PMID: 35644181 PMCID: PMC9178707 DOI: 10.1016/bs.mie.2021.12.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The B12-dependent radical SAM enzymes are an emerging subgroup of biological catalysts that bind a cobalamin cofactor in addition to the canonical [Fe4S4] cluster characteristic of radical SAM enzymes. Most of the B12-dependent radical SAM enzymes that have been characterized mediated methyltransfer reactions; however, a small number are known to catalyze more diverse reactions such as ring contractions. Thus, Genk is a methyltransferase from the gentamicin C biosynthetic pathway, whereas OxsB catalyzes the oxidative ring contraction of 2'-deoxyadenosine 5'-phosphates to generate an oxetane aldehyde during the biosynthesis of oxetanocin A. The preparation and in vitro characterization of such enzymes is complicated by the presence of two redox sensitive cofactors in addition to challenges in obtaining soluble protein for study. This chapter describes expression, purification and assay methodologies for GenK and OxsB highlighting the use of denaturation/refolding protocols for solubilizing inclusion bodies as well as the use of cluster assembly and cobalamin uptake machinery during in vivo expression.
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Affiliation(s)
- Yu-Hsuan Lee
- Department of Chemistry, University of Texas at Austin, Austin, TX, United States
| | - Hung-Wen Liu
- Department of Chemistry, University of Texas at Austin, Austin, TX, United States; Division of Chemical Biology and Medicinal Chemistry, College of Pharmacy, University of Texas at Austin, Austin, TX, United States.
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10
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Mital S, Christie G, Dikicioglu D. Recombinant expression of insoluble enzymes in Escherichia coli: a systematic review of experimental design and its manufacturing implications. Microb Cell Fact 2021; 20:208. [PMID: 34717620 PMCID: PMC8557517 DOI: 10.1186/s12934-021-01698-w] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Accepted: 10/22/2021] [Indexed: 02/06/2023] Open
Abstract
Recombinant enzyme expression in Escherichia coli is one of the most popular methods to produce bulk concentrations of protein product. However, this method is often limited by the inadvertent formation of inclusion bodies. Our analysis systematically reviews literature from 2010 to 2021 and details the methods and strategies researchers have utilized for expression of difficult to express (DtE), industrially relevant recombinant enzymes in E. coli expression strains. Our review identifies an absence of a coherent strategy with disparate practices being used to promote solubility. We discuss the potential to approach recombinant expression systematically, with the aid of modern bioinformatics, modelling, and ‘omics’ based systems-level analysis techniques to provide a structured, holistic approach. Our analysis also identifies potential gaps in the methods used to report metadata in publications and the impact on the reproducibility and growth of the research in this field.
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Affiliation(s)
- Suraj Mital
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge, CB3 0AS, UK
| | - Graham Christie
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge, CB3 0AS, UK
| | - Duygu Dikicioglu
- Department of Biochemical Engineering, University College London, London, WC1E 6BT, UK.
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11
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Benjdia A, Berteau O. Radical SAM Enzymes and Ribosomally-Synthesized and Post-translationally Modified Peptides: A Growing Importance in the Microbiomes. Front Chem 2021; 9:678068. [PMID: 34350157 PMCID: PMC8326336 DOI: 10.3389/fchem.2021.678068] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Accepted: 06/07/2021] [Indexed: 11/13/2022] Open
Abstract
To face the current antibiotic resistance crisis, novel strategies are urgently required. Indeed, in the last 30 years, despite considerable efforts involving notably high-throughput screening and combinatorial libraries, only few antibiotics have been launched to the market. Natural products have markedly contributed to the discovery of novel antibiotics, chemistry and drug leads, with more than half anti-infective and anticancer drugs approved by the FDA being of natural origin or inspired by natural products. Among them, thanks to their modular structure and simple biosynthetic logic, ribosomally synthesized and posttranslationally modified peptides (RiPPs) are promising scaffolds. In addition, recent studies have highlighted the pivotal role of RiPPs in the human microbiota which remains an untapped source of natural products. In this review, we report on recent developments in radical SAM enzymology and how these unique biocatalysts have been shown to install complex and sometimes unprecedented posttranslational modifications in RiPPs with a special focus on microbiome derived enzymes.
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Affiliation(s)
- Alhosna Benjdia
- Université Paris-Saclay, INRAE, AgroParisTech, Micalis Institute, ChemSyBio, Jouy-en-Josas, France
| | - Olivier Berteau
- Université Paris-Saclay, INRAE, AgroParisTech, Micalis Institute, ChemSyBio, Jouy-en-Josas, France
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12
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Zhang H, Ge H, Zhang Y, Wang Y, Zhang P. Slr0320 Is Crucial for Optimal Function of Photosystem II during High Light Acclimation in Synechocystis sp. PCC 6803. Life (Basel) 2021; 11:life11040279. [PMID: 33810453 PMCID: PMC8065906 DOI: 10.3390/life11040279] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Revised: 03/20/2021] [Accepted: 03/24/2021] [Indexed: 11/16/2022] Open
Abstract
Upon exposure of photosynthetic organisms to high light (HL), several HL acclimation responses are triggered. Herein, we identified a novel gene, slr0320, critical for HL acclimation in Synechocystis sp. PCC 6803. The growth rate of the Δslr0320 mutant was similar to wild type (WT) under normal light (NL) but severely declined under HL. Net photosynthesis of the mutant was lower under HL, but maximum photosystem II (PSII) activity was higher under NL and HL. Immunodetection revealed the accumulation and assembly of PSII were similar between WT and the mutant. Chlorophyll fluorescence traces showed the stable fluorescence of the mutant under light was much higher. Kinetics of single flash-induced chlorophyll fluorescence increase and decay revealed the slower electron transfer from QA to QB in the mutant. These data indicate that, in the Δslr0320 mutant, the number of functional PSIIs was comparable to WT even under HL but the electron transfer between QA and QB was inefficient. Quantitative proteomics and real-time PCR revealed that expression profiles of psbL, psbH and psbI were significantly altered in the Δslr0320 mutant. Thus, Slr0320 protein plays critical roles in optimizing PSII activity during HL acclimation and is essential for PSII electron transfer from QA to QB.
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Affiliation(s)
- Hao Zhang
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, China; (H.Z.); (Y.Z.)
| | - Haitao Ge
- Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China; (H.G.); (Y.W.)
| | - Ye Zhang
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, China; (H.Z.); (Y.Z.)
| | - Yingchun Wang
- Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China; (H.G.); (Y.W.)
| | - Pengpeng Zhang
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, China; (H.Z.); (Y.Z.)
- Correspondence:
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13
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Zhong A, Lee YH, Liu YN, Liu HW. Biosynthesis of Oxetanocin-A Includes a B 12-Dependent Radical SAM Enzyme That Can Catalyze both Oxidative Ring Contraction and the Demethylation of SAM. Biochemistry 2021; 60:537-546. [PMID: 33560833 DOI: 10.1021/acs.biochem.0c00915] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Oxetanocin-A is an antitumor, antiviral, and antibacterial nucleoside. It is biosynthesized via the oxidative ring contraction of a purine nucleoside co-opted from primary metabolism. This reaction is catalyzed by a B12-dependent radical S-adenosyl-l-methionine (SAM) enzyme, OxsB, and a phosphohydrolase, OxsA. Previous experiments showed that the product of the OxsB/OxsA-catalyzed reaction is an oxetane aldehyde produced alongside an uncharacterized byproduct. Experiments reported herein reveal that OxsB/OxsA complex formation is crucial for the ring contraction reaction and that reduction of the aldehyde intermediate is catalyzed by a nonspecific dehydrogenase from the general cellular pool. In addition, the byproduct is identified as a 1,3-thiazinane adduct between the aldehyde and l-homocysteine. While homocysteine was never included in the OxsB/OxsA assays, the data suggest that it can be generated from SAM via S-adenosyl-l-homocysteine (SAH). Further study revealed that conversion of SAM to SAH is facilitated by OxsB; however, the subsequent conversion of SAH to homocysteine is due to protein contaminants that co-purify with OxsA. Nevertheless, the observed demethylation of SAM to SAH suggests possible methyltransferase activity of OxsB, and substrate methylation was indeed detected in the OxsB-catalyzed reaction. This work is significant because it not only completes the description of the oxetanocin-A biosynthetic pathway but also suggests that OxsB may be capable of methyltransferase activity.
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14
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Shiraishi T, Kuzuyama T. Biosynthetic pathways and enzymes involved in the production of phosphonic acid natural products. Biosci Biotechnol Biochem 2021; 85:42-52. [PMID: 33577658 DOI: 10.1093/bbb/zbaa052] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Accepted: 10/04/2020] [Indexed: 02/07/2023]
Abstract
Phosphonates are organophosphorus compounds possessing a characteristic C-P bond in which phosphorus is directly bonded to carbon. As phosphonates mimic the phosphates and carboxylates of biological molecules to potentially inhibit metabolic enzymes, they could be lead compounds for the development of a variety of drugs. Fosfomycin (FM) is a representative phosphonate natural product that is widely used as an antibacterial drug. Here, we review the biosynthesis of FM, which includes a recent breakthrough to find a missing link in the biosynthetic pathway that had been a mystery for a quarter-century. In addition, we describe the genome mining of phosphonate natural products using the biosynthetic gene encoding an enzyme that catalyzes C-P bond formation. We also introduce the chemoenzymatic synthesis of phosphonate derivatives. These studies expand the repertoires of phosphonates and the related biosynthetic machinery. This review mainly covers the years 2012-2020.
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Affiliation(s)
- Taro Shiraishi
- Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Tomohisa Kuzuyama
- Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
- Collaborative Research Institute for Innovative Microbiology (CRIIM), The University of Tokyo, Bunkyo-ku, Tokyo, Japan
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15
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Cao Y, Peng Q, Li S, Deng Z, Gao J. The intriguing biology and chemistry of fosfomycin: the only marketed phosphonate antibiotic. RSC Adv 2019; 9:42204-42218. [PMID: 35548698 PMCID: PMC9088020 DOI: 10.1039/c9ra08299a] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Accepted: 11/27/2019] [Indexed: 11/29/2022] Open
Abstract
Recently infectious diseases caused by the increased emergence and rapid spread of drug-resistant bacterial isolates have been one of the main threats to global public health because of a marked surge in both morbidity and mortality. The only phosphonate antibiotic in the clinic, fosfomycin, is a small broad-spectrum molecule that effectively inhibits the initial step in peptidoglycan biosynthesis by blocking the enzyme, MurA in both Gram-positive and Gram-negative bacteria. As fosfomycin has a novel mechanism of action, low toxicity, a broad spectrum of antibacterial activity, excellent pharmacodynamic/pharmacokinetic properties, and good bioavailability, it has been approved for clinical use in the treatment of urinary tract bacterial infections in many countries for several decades. Furthermore, its potential use for difficult-to-treat bacterial infections has become promising, and fosfomycin has become an ideal candidate for the effective treatment of bacterial infections caused by multidrug-resistant isolates, especially in combination with other therapeutic drugs. Here we aim to present an overview of the biology and chemistry of fosfomycin including isolation and characterization, pharmacology, biosynthesis and chemical synthesis since its discovery in order to not only help scientists reassess the role of this exciting drug in fighting antibiotic resistance but also build the stage for discovering more novel phosphonate antibiotics in the future.
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Affiliation(s)
- Yingying Cao
- College of Life Sciences, Fujian Agriculture and Forestry University Fuzhou 350002 China
| | - Qingyao Peng
- College of Life Sciences, Fujian Agriculture and Forestry University Fuzhou 350002 China
| | - Shanni Li
- College of Life Sciences, Fujian Agriculture and Forestry University Fuzhou 350002 China
| | - Zixin Deng
- State Key Laboratory of Microbial Metabolism, Joint International Laboratory on Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University 800 Dongchuan Road Shanghai 200240 China
| | - Jiangtao Gao
- College of Life Sciences, Fujian Agriculture and Forestry University Fuzhou 350002 China
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16
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Mathew LG, Beattie NR, Pritchett C, Lanzilotta WN. New Insight into the Mechanism of Anaerobic Heme Degradation. Biochemistry 2019; 58:4641-4654. [PMID: 31652058 DOI: 10.1021/acs.biochem.9b00841] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
ChuW, ChuX, and ChuY are contiguous genes downstream from a single promoter that are expressed in the enteric pathogen Escherichia coli O157:H7 when iron is limiting. These genes, and the corresponding proteins, are part of a larger heme uptake and utilization operon that is common to several other enteric pathogens, such as Vibrio cholerae. The aerobic degradation of heme has been well characterized in humans and several pathogenic bacteria, including E. coli O157:H7, but only recently was it shown that ChuW catalyzes the anaerobic degradation of heme to release iron and produce a reactive tetrapyrrole termed "anaerobilin". ChuY has been shown to function as an anaerobilin reductase, in a role that parallels biliverdin reductase. In this work we have employed biochemical and biophysical approaches to further interrogate the mechanism of the anaerobic degradation of heme. We demonstrate that the iron atom of the heme does not participate in the catalytic mechanism of ChuW and that S-adenosyl-l-methionine binding induces conformational changes that favor catalysis. In addition, we show that ChuX and ChuY have synergistic and additive effects on the turnover rate of ChuW. Finally, we have found that ChuS is an effective source of heme or protoporphyrin IX for ChuW under anaerobic conditions. These data indicate that ChuS may have dual functionality in vivo. Specifically, ChuS serves as a heme oxygenase during aerobic metabolism of heme but functions as a cytoplasmic heme storage protein under anaerobic conditions, akin to what has been shown for PhuS (45% sequence identity) from Pseudomonas aeruginosa.
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Affiliation(s)
- Liju G Mathew
- Department of Biochemistry and Molecular Biology & Center for Metalloenzyme Studies , University of Georgia , Athens , Georgia 30602 , United States
| | - Nathaniel R Beattie
- Department of Biochemistry and Molecular Biology & Center for Metalloenzyme Studies , University of Georgia , Athens , Georgia 30602 , United States
| | - Clayton Pritchett
- Department of Biochemistry and Molecular Biology & Center for Metalloenzyme Studies , University of Georgia , Athens , Georgia 30602 , United States
| | - William N Lanzilotta
- Department of Biochemistry and Molecular Biology & Center for Metalloenzyme Studies , University of Georgia , Athens , Georgia 30602 , United States
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17
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Sokolovskaya OM, Mok KC, Park JD, Tran JLA, Quanstrom KA, Taga ME. Cofactor Selectivity in Methylmalonyl Coenzyme A Mutase, a Model Cobamide-Dependent Enzyme. mBio 2019; 10:e01303-19. [PMID: 31551329 PMCID: PMC6759758 DOI: 10.1128/mbio.01303-19] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Accepted: 08/23/2019] [Indexed: 12/25/2022] Open
Abstract
Cobamides, a uniquely diverse family of enzyme cofactors related to vitamin B12, are produced exclusively by bacteria and archaea but used in all domains of life. While it is widely accepted that cobamide-dependent organisms require specific cobamides for their metabolism, the biochemical mechanisms that make cobamides functionally distinct are largely unknown. Here, we examine the effects of cobamide structural variation on a model cobamide-dependent enzyme, methylmalonyl coenzyme A (CoA) mutase (MCM). The in vitro binding affinity of MCM for cobamides can be dramatically influenced by small changes in the structure of the lower ligand of the cobamide, and binding selectivity differs between bacterial orthologs of MCM. In contrast, variations in the lower ligand have minor effects on MCM catalysis. Bacterial growth assays demonstrate that cobamide requirements of MCM in vitro largely correlate with in vivo cobamide dependence. This result underscores the importance of enzyme selectivity in the cobamide-dependent physiology of bacteria.IMPORTANCE Cobamides, including vitamin B12, are enzyme cofactors used by organisms in all domains of life. Cobamides are structurally diverse, and microbial growth and metabolism vary based on cobamide structure. Understanding cobamide preference in microorganisms is important given that cobamides are widely used and appear to mediate microbial interactions in host-associated and aquatic environments. Until now, the biochemical basis for cobamide preferences was largely unknown. In this study, we analyzed the effects of the structural diversity of cobamides on a model cobamide-dependent enzyme, methylmalonyl-CoA mutase (MCM). We found that very small changes in cobamide structure could dramatically affect the binding affinity of cobamides to MCM. Strikingly, cobamide-dependent growth of a model bacterium, Sinorhizobium meliloti, largely correlated with the cofactor binding selectivity of S. meliloti MCM, emphasizing the importance of cobamide-dependent enzyme selectivity in bacterial growth and cobamide-mediated microbial interactions.
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Affiliation(s)
- Olga M Sokolovskaya
- Department of Plant & Microbial Biology, University of California Berkeley, Berkeley, California, USA
- Department of Chemistry, University of California Berkeley, Berkeley, California, USA
| | - Kenny C Mok
- Department of Plant & Microbial Biology, University of California Berkeley, Berkeley, California, USA
| | - Jong Duk Park
- Department of Plant & Microbial Biology, University of California Berkeley, Berkeley, California, USA
| | - Jennifer L A Tran
- Department of Plant & Microbial Biology, University of California Berkeley, Berkeley, California, USA
| | - Kathryn A Quanstrom
- Department of Plant & Microbial Biology, University of California Berkeley, Berkeley, California, USA
| | - Michiko E Taga
- Department of Plant & Microbial Biology, University of California Berkeley, Berkeley, California, USA
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18
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Wang SC. Cobalamin-dependent radical S-adenosyl-l-methionine enzymes in natural product biosynthesis. Nat Prod Rep 2019; 35:707-720. [PMID: 30079906 DOI: 10.1039/c7np00059f] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Covering: 2011 to 2018 This highlight summarizes the investigation of cobalamin (Cbl)- and radical S-adenosyl-l-methionine (SAM)-dependent enzymes found in natural product biosynthesis to date and suggests some possibilities for the future. Though some mechanistic aspects are apparently shared, the overall diversity of this family's functions and abilities is significant and may be tailored to the specific substrate and/or reaction being catalyzed. A little over a year ago, the first crystal structure of a Cbl- and radical SAM-dependent enzyme was solved, providing the first insight into what may be the shared scaffolding of these enzymes.
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Affiliation(s)
- Susan C Wang
- Case Western Reserve University School of Medicine, Department of Biochemistry, USA.
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19
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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: 43] [Impact Index Per Article: 8.6] [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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20
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Wang B, Blaszczyk A, Knox HL, Zhou S, Blaesi EJ, Krebs C, Wang RX, Booker SJ. Stereochemical and Mechanistic Investigation of the Reaction Catalyzed by Fom3 from Streptomyces fradiae, a Cobalamin-Dependent Radical S-Adenosylmethionine Methylase. Biochemistry 2018; 57:4972-4984. [PMID: 30036047 PMCID: PMC6554712 DOI: 10.1021/acs.biochem.8b00693] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Fom3, a cobalamin-dependent radical S-adenosylmethionine (SAM) methylase, has recently been shown to catalyze the methylation of carbon 2″ of cytidylyl-2-hydroxyethylphosphonate (HEP-CMP) to form cytidylyl-2-hydroxypropylphosphonate (HPP-CMP) during the biosynthesis of fosfomycin, a broad-spectrum antibiotic. It has been hypothesized that a 5'-deoxyadenosyl 5'-radical (5'-dA•) generated from the reductive cleavage of SAM abstracts a hydrogen atom from HEP-CMP to prime the substrate for addition of a methyl group from methylcobalamin (MeCbl); however, the mechanistic details of this reaction remain elusive. Moreover, it has been reported that Fom3 catalyzes the methylation of HEP-CMP to give a mixture of the ( S)-HPP and ( R)-HPP stereoisomers, which is rare for an enzyme-catalyzed reaction. Herein, we describe a detailed biochemical investigation of a Fom3 that is purified with 1 equiv of its cobalamin cofactor bound, which is almost exclusively in the form of MeCbl. Electron paramagnetic resonance and Mössbauer spectroscopies confirm that Fom3 contains one [4Fe-4S] cluster. Using deuterated enantiomers of HEP-CMP, we demonstrate that the 5'-dA• generated by Fom3 abstracts the C2″- pro-R hydrogen of HEP-CMP and that methyl addition takes place with inversion of configuration to yield solely ( S)-HPP-CMP. Fom3 also sluggishly converts cytidylyl-ethylphosphonate to the corresponding methylated product but more readily acts on cytidylyl-2-fluoroethylphosphonate, which exhibits a lower C2″ homolytic bond-dissociation energy. Our studies suggest a mechanism in which the substrate C2″ radical, generated upon hydrogen atom abstraction by the 5'-dA•, directly attacks MeCbl to transfer a methyl radical (CH3•) rather than a methyl cation (CH3+), directly forming cob(II)alamin in the process.
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Affiliation(s)
- Bo Wang
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Anthony Blaszczyk
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Hayley L. Knox
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Shengbin Zhou
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Elizabeth J. Blaesi
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Carsten Krebs
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Roy X. Wang
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Squire J. Booker
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
- Howard Hughes Medical Institute, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
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21
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Sato S, Kudo F, Kuzuyama T, Hammerschmidt F, Eguchi T. C-Methylation Catalyzed by Fom3, a Cobalamin-Dependent Radical S-adenosyl-l-methionine Enzyme in Fosfomycin Biosynthesis, Proceeds with Inversion of Configuration. Biochemistry 2018; 57:4963-4966. [PMID: 29966085 DOI: 10.1021/acs.biochem.8b00614] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Fom3, a cobalamin-dependent radical S-adenosyl-l-methionine (SAM) methyltransferase, catalyzes C-methylation at the C2 position of cytidylylated 2-hydroxyethylphosphonate (HEP-CMP) to afford cytidylylated 2-hydroxypropylphosphonate (HPP-CMP) in fosfomycin biosynthesis. In this study, the Fom3 reaction product HPP-CMP was reanalyzed by chiral ligand exchange chromatography to confirm its stereochemistry. The Fom3 methylation product was found to be ( S)-HPP-CMP only, indicating that the stereochemistry of the C-methylation catalyzed by Fom3 is ( S)-selective. In addition, Fom3 reaction was performed with ( S)-[2-2H1]HEP-CMP and ( R)-[2-2H1]HEP-CMP to elucidate the stereoselectivity during the abstraction of the hydrogen atom from C2 of HEP-CMP. Liquid chromatography-electrospray ionization mass spectrometry analysis of the 5'-deoxyadenosine produced showed that the 2H atom of ( R)-[2-2H1]HEP-CMP was incorporated into 5'-deoxyadenosine but that from ( S)-[2-2H1]HEP-CMP was not. Retention of the 2H atom of ( S)-[2-2H1]HEP-CMP in HPP-CMP was also observed. These results indicate that the 5'-deoxyadenosyl radical stereoselectively abstracts the pro-R hydrogen atom at the C2 position of HEP-CMP and the substrate radical intermediate reacts with the methyl group on cobalamin that is located on the opposite side of the substrate from SAM. Consequently, it was clarified that the C-methylation catalyzed by Fom3 proceeds with inversion of configuration.
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Affiliation(s)
- Shusuke Sato
- Department of Chemistry , Tokyo Institute of Technology , 2-12-1 O-okayama , Meguro-ku, Tokyo 152-8551 , Japan
| | - Fumitaka Kudo
- Department of Chemistry , Tokyo Institute of Technology , 2-12-1 O-okayama , Meguro-ku, Tokyo 152-8551 , Japan
| | - Tomohisa Kuzuyama
- Biotechnology Research Center, Collaborative Research Institute for Innovative Microbiology , The University of Tokyo , 1-1-1 Yayoi , Bunkyo-ku, Tokyo 113-8657 , Japan
| | - Friedrich Hammerschmidt
- Institute of Organic Chemistry , University of Vienna , Währingerstraße 38 , A-1090 Vienna , Austria
| | - Tadashi Eguchi
- Department of Chemistry , Tokyo Institute of Technology , 2-12-1 O-okayama , Meguro-ku, Tokyo 152-8551 , Japan
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22
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Yan F, Auerbach D, Chai Y, Keller L, Tu Q, Hüttel S, Glemser A, Grab HA, Bach T, Zhang Y, Müller R. Biosynthesis and Heterologous Production of Vioprolides: Rational Biosynthetic Engineering and Unprecedented 4‐Methylazetidinecarboxylic Acid Formation. Angew Chem Int Ed Engl 2018; 57:8754-8759. [DOI: 10.1002/anie.201802479] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Revised: 04/08/2018] [Indexed: 11/07/2022]
Affiliation(s)
- Fu Yan
- Helmholtz Institute for Pharmaceutical Research Saarland (HIPS) Helmholtz Center for Infection Research, and Department of Pharmacy Saarland University Campus Building E8.1 66123 Saarbrücken Germany
| | - David Auerbach
- Helmholtz Institute for Pharmaceutical Research Saarland (HIPS) Helmholtz Center for Infection Research, and Department of Pharmacy Saarland University Campus Building E8.1 66123 Saarbrücken Germany
| | - Yi Chai
- Helmholtz Institute for Pharmaceutical Research Saarland (HIPS) Helmholtz Center for Infection Research, and Department of Pharmacy Saarland University Campus Building E8.1 66123 Saarbrücken Germany
| | - Lena Keller
- Helmholtz Institute for Pharmaceutical Research Saarland (HIPS) Helmholtz Center for Infection Research, and Department of Pharmacy Saarland University Campus Building E8.1 66123 Saarbrücken Germany
| | - Qiang Tu
- Helmholtz Institute for Pharmaceutical Research Saarland (HIPS) Helmholtz Center for Infection Research, and Department of Pharmacy Saarland University Campus Building E8.1 66123 Saarbrücken Germany
| | - Stephan Hüttel
- Helmholtz Centre for Infection Research Department of Microbial Drugs Braunschweig Germany
| | - Amelie Glemser
- Helmholtz Centre for Infection Research Department of Microbial Drugs Braunschweig Germany
| | - Hanusch A. Grab
- Lehrstuhl für Organische Chemie I Technische Universität München Lichtenbergstrasse 4 85747 Garching Germany
| | - Thorsten Bach
- Lehrstuhl für Organische Chemie I Technische Universität München Lichtenbergstrasse 4 85747 Garching Germany
| | - Youming Zhang
- Shandong University-Helmholtz Joint Institute of Biotechnology State Key Laboratory of Microbial Technology School of Life Science Shandong University Qingdao P. R. China
| | - Rolf Müller
- Helmholtz Institute for Pharmaceutical Research Saarland (HIPS) Helmholtz Center for Infection Research, and Department of Pharmacy Saarland University Campus Building E8.1 66123 Saarbrücken Germany
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23
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Yan F, Auerbach D, Chai Y, Keller L, Tu Q, Hüttel S, Glemser A, Grab HA, Bach T, Zhang Y, Müller R. Biosynthese und heterologe Expression der Vioprolide: rationale gentechnische Eingriffe in die Biosynthese und 4‐Methylazetidincarbonsäure‐Bildung. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201802479] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Fu Yan
- Helmholtz-Institut für Pharmazeutische Forschung Saarland (HIPS) Helmholtz-Zentrum für Infektionsforschung und Pharmazeutische Biotechnologie Universität des Saarlands Campus Gebäude E8.1 66123 Saarbrücken Deutschland
| | - David Auerbach
- Helmholtz-Institut für Pharmazeutische Forschung Saarland (HIPS) Helmholtz-Zentrum für Infektionsforschung und Pharmazeutische Biotechnologie Universität des Saarlands Campus Gebäude E8.1 66123 Saarbrücken Deutschland
| | - Yi Chai
- Helmholtz-Institut für Pharmazeutische Forschung Saarland (HIPS) Helmholtz-Zentrum für Infektionsforschung und Pharmazeutische Biotechnologie Universität des Saarlands Campus Gebäude E8.1 66123 Saarbrücken Deutschland
| | - Lena Keller
- Helmholtz-Institut für Pharmazeutische Forschung Saarland (HIPS) Helmholtz-Zentrum für Infektionsforschung und Pharmazeutische Biotechnologie Universität des Saarlands Campus Gebäude E8.1 66123 Saarbrücken Deutschland
| | - Qiang Tu
- Helmholtz-Institut für Pharmazeutische Forschung Saarland (HIPS) Helmholtz-Zentrum für Infektionsforschung und Pharmazeutische Biotechnologie Universität des Saarlands Campus Gebäude E8.1 66123 Saarbrücken Deutschland
| | - Stephan Hüttel
- Helmholtz-Zentrum für Infektionsforschung (HZI) Abteilung Mikrobielle Wirkstoffe Braunschweig Deutschland
| | - Amelie Glemser
- Helmholtz-Zentrum für Infektionsforschung (HZI) Abteilung Mikrobielle Wirkstoffe Braunschweig Deutschland
| | - Hanusch A. Grab
- Lehrstuhl für Organische Chemie I Technische Universität München Lichtenbergstraße 4 85747 Garching Deutschland
| | - Thorsten Bach
- Lehrstuhl für Organische Chemie I Technische Universität München Lichtenbergstraße 4 85747 Garching Deutschland
| | - Youming Zhang
- Shandong University-Helmholtz Joint Institute of Biotechnology State Key Laboratory of Microbial Technology School of Life Science Shandong University Qingdao VR China
| | - Rolf Müller
- Helmholtz-Institut für Pharmazeutische Forschung Saarland (HIPS) Helmholtz-Zentrum für Infektionsforschung und Pharmazeutische Biotechnologie Universität des Saarlands Campus Gebäude E8.1 66123 Saarbrücken Deutschland
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24
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Schweifer A, Hammerschmidt F. Stereochemical Course of Methyl Transfer by Cobalamin-Dependent Radical SAM Methyltransferase in Fosfomycin Biosynthesis. Biochemistry 2018; 57:2069-2073. [PMID: 29578699 DOI: 10.1021/acs.biochem.8b00264] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The methyl groups of [ methyl-( S)]- and [ methyl-( R)]-[ methyl-D,T]-l-methionine fed to Streptomyces fradiae were incorporated into fosfomycin, which was chemically degraded to chiral AcONa. The enzymatic test gave the ( S)-configuration for the chiral AcONa derived from methionine with the ( S)-[D,T]methyl group ( F = 31.7) and ( R) for the one derived from methionine with the ( R)-[D,T]methyl group ( F = 83.0). The radical SAM methyltransferase transfers the methyl group of MeCbl to HEP-CMP with inversion of configuration.
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Affiliation(s)
- Anna Schweifer
- Institute of Organic Chemistry , University of Vienna , Währingerstraße 38 , A-1090 Vienna , Austria
| | - Friedrich Hammerschmidt
- Institute of Organic Chemistry , University of Vienna , Währingerstraße 38 , A-1090 Vienna , Austria
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25
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Lanz ND, Blaszczyk AJ, McCarthy EL, Wang B, Wang RX, Jones BS, Booker SJ. Enhanced Solubilization of Class B Radical S-Adenosylmethionine Methylases by Improved Cobalamin Uptake in Escherichia coli. Biochemistry 2018; 57:1475-1490. [PMID: 29298049 DOI: 10.1021/acs.biochem.7b01205] [Citation(s) in RCA: 54] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The methylation of unactivated carbon and phosphorus centers is a burgeoning area of biological chemistry, especially given that such reactions constitute key steps in the biosynthesis of numerous enzyme cofactors, antibiotics, and other natural products of clinical value. These kinetically challenging reactions are catalyzed exclusively by enzymes in the radical S-adenosylmethionine (SAM) superfamily and have been grouped into four classes (A-D). Class B radical SAM (RS) methylases require a cobalamin cofactor in addition to the [4Fe-4S] cluster that is characteristic of RS enzymes. However, their poor solubility upon overexpression and their generally poor turnover has hampered detailed in vitro studies of these enzymes. It has been suggested that improper folding, possibly caused by insufficient cobalamin during their overproduction in Escherichia coli, leads to formation of inclusion bodies. Herein, we report our efforts to improve the overproduction of class B RS methylases in a soluble form by engineering a strain of E. coli to take in more cobalamin. We cloned five genes ( btuC, btuE, btuD, btuF, and btuB) that encode proteins that are responsible for cobalamin uptake and transport in E. coli and co-expressed these genes with those that encode TsrM, Fom3, PhpK, and ThnK, four class B RS methylases that suffer from poor solubility during overproduction. This strategy markedly enhances the uptake of cobalamin into the cytoplasm and improves the solubility of the target enzymes significantly.
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26
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Zhang Z, Mahanta N, Hudson GA, Mitchell DA, van der Donk WA. Mechanism of a Class C Radical S-Adenosyl-l-methionine Thiazole Methyl Transferase. J Am Chem Soc 2017; 139:18623-18631. [PMID: 29190095 PMCID: PMC5748327 DOI: 10.1021/jacs.7b10203] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The past decade has seen the discovery of four different classes of radical S-adenosylmethionine (rSAM) methyltransferases that methylate unactivated carbon centers. Whereas the mechanism of class A is well understood, the molecular details of methylation by classes B-D are not. In this study, we present detailed mechanistic investigations of the class C rSAM methyltransferase TbtI involved in the biosynthesis of the potent thiopeptide antibiotic thiomuracin. TbtI C-methylates a Cys-derived thiazole during posttranslational maturation. Product analysis demonstrates that two SAM molecules are required for methylation and that one SAM (SAM1) is converted to 5'-deoxyadenosine and the second SAM (SAM2) is converted to S-adenosyl-l-homocysteine (SAH). Isotope labeling studies show that a hydrogen is transferred from the methyl group of SAM2 to the 5'-deoxyadenosine of SAM1 and the other two hydrogens of the methyl group of SAM2 appear in the methylated product. In addition, a hydrogen appears to be transferred from the β-position of the thiazole to the methyl group in the product. We also show that the methyl protons in the product can exchange with solvent. A mechanism consistent with these observations is presented that differs from other characterized radical SAM methyltransferases.
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Affiliation(s)
- Zhengan Zhang
- Department of Chemistry, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States.,Howard Hughes Medical Institute, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
| | - Nilkamal Mahanta
- Department of Chemistry, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States.,Institute for Genomic Biology, University of Illinois at Urbana-Champaign , 1206 West Gregory Drive, Urbana, Illinois 61801, United States
| | - Graham A Hudson
- Department of Chemistry, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
| | - Douglas A Mitchell
- Department of Chemistry, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States.,Institute for Genomic Biology, University of Illinois at Urbana-Champaign , 1206 West Gregory Drive, Urbana, Illinois 61801, United States
| | - Wilfred A van der Donk
- Department of Chemistry, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States.,Howard Hughes Medical Institute, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States.,Institute for Genomic Biology, University of Illinois at Urbana-Champaign , 1206 West Gregory Drive, Urbana, Illinois 61801, United States
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27
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Kim HJ, Liu YN, McCarty RM, Liu HW. Reaction Catalyzed by GenK, a Cobalamin-Dependent Radical S-Adenosyl-l-methionine Methyltransferase in the Biosynthetic Pathway of Gentamicin, Proceeds with Retention of Configuration. J Am Chem Soc 2017; 139:16084-16087. [PMID: 29091410 DOI: 10.1021/jacs.7b09890] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Many cobalamin (Cbl)-dependent radical S-adenosyl-l-methionine (SAM) methyltransferases have been identified through sequence alignment and/or genetic analysis; however, few have been studied in vitro. GenK is one such enzyme that catalyzes methylation of the 6'-carbon of gentamicin X2 (GenX2) to produce G418 during the biosynthesis of gentamicins. Reported herein, several alternative substrates and fluorinated substrate analogs were prepared to investigate the mechanism of methyl transfer from Cbl to the substrate as well as the substrate specificity of GenK. Experiments with deuterated substrates are also shown here to demonstrate that the 6'-pro-R-hydrogen atom of GenX2 is stereoselectively abstracted by the 5'-dAdo· radical and that methylation occurs with retention of configuration at C6'. Based on these observations, a model of GenK catalysis is proposed wherein free rotation of the radical-bearing carbon is prevented and the radical SAM machinery sits adjacent rather than opposite to the Me-Cbl cofactor with respect to the substrate in the enzyme active site.
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Affiliation(s)
- Hak Joong Kim
- Division of Chemical Biology and Medicinal Chemistry, College of Pharmacy, and Department of Chemistry, University of Texas at Austin , Austin, Texas 78712, United States
| | - Yung-Nan Liu
- Division of Chemical Biology and Medicinal Chemistry, College of Pharmacy, and Department of Chemistry, University of Texas at Austin , Austin, Texas 78712, United States
| | - Reid M McCarty
- Division of Chemical Biology and Medicinal Chemistry, College of Pharmacy, and Department of Chemistry, University of Texas at Austin , Austin, Texas 78712, United States
| | - Hung-Wen Liu
- Division of Chemical Biology and Medicinal Chemistry, College of Pharmacy, and Department of Chemistry, University of Texas at Austin , Austin, Texas 78712, United States
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28
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Blaszczyk AJ, Wang B, Silakov A, Ho JV, Booker SJ. Efficient methylation of C2 in l-tryptophan by the cobalamin-dependent radical S-adenosylmethionine methylase TsrM requires an unmodified N1 amine. J Biol Chem 2017; 292:15456-15467. [PMID: 28747433 PMCID: PMC5602403 DOI: 10.1074/jbc.m117.778548] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Revised: 07/20/2017] [Indexed: 11/06/2022] Open
Abstract
TsrM catalyzes the methylation of C2 in l-tryptophan (Trp). This reaction is the first step in the biosynthesis of the quinaldic acid moiety of the thiopeptide antibiotic thiostrepton, which exhibits potent activity against Gram-positive pathogens. TsrM is a member of the radical S-adenosylmethionine (SAM) superfamily of enzymes, but it does not catalyze the formation of 5'-deoxyadenosin-5'-yl or any other SAM-derived radical. In addition to a [4Fe-4S] cluster, TsrM contains a cobalamin cofactor that serves as an intermediate methyl carrier in its reaction. However, how this cofactor donates a methyl moiety to the Trp substrate is unknown. Here, we showed that the unmodified N1 position of Trp is important for turnover and that 1-thia-Trp and 1-oxa-Trp serve as competitive inhibitors. We also showed that β-cyclopropyl-Trp undergoes C2 methylation in the absence of cyclopropyl ring opening, disfavoring mechanisms that involve unpaired electron density at C3 of the indole ring. Moreover, we showed that all other indole-substituted analogs of Trp undergo methylation at varying but measurable rates and that the analog 7-aza-Trp, which is expected to temper the nucleophilicity of C2 in Trp, is a very poor substrate. Last, no formation of cob(II)alamin or substrate radicals was observed during the reaction with Trp or any molecule within a tested panel of Trp analogs. In summary, our results are most consistent with a mechanism that involves two polar nucleophilic displacements, the second of which requires deprotonation of the indole nitrogen in Trp during its attack on methylcobalamin.
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Affiliation(s)
| | - Bo Wang
- the Department of Chemistry, and
| | | | | | - Squire J Booker
- From the Department of Biochemistry and Molecular Biology,
- the Department of Chemistry, and
- the Howard Hughes Medical Institute, The Pennsylvania State University, University Park, Pennsylvania 16802
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29
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TsrM as a Model for Purifying and Characterizing Cobalamin-Dependent Radical S-Adenosylmethionine Methylases. Methods Enzymol 2017; 595:303-329. [PMID: 28882204 DOI: 10.1016/bs.mie.2017.07.007] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Cobalamin-dependent radical S-adenosylmethionine (SAM) methylases play vital roles in the de novo biosynthesis of many antibiotics, cofactors, and other important natural products, yet remain an understudied subclass of radical SAM enzymes. In addition to a [4Fe-4S] cluster that is ligated by three cysteine residues, these enzymes also contain an N-terminal cobalamin-binding domain. In vitro studies of these enzymes have been severely limited because many are insoluble or sparingly soluble upon their overproduction in Escherichia coli. This solubility issue has led a number of groups either to purify the protein from inclusion bodies or to purify soluble protein that often lacks proper cofactor incorporation. Herein, we use TsrM as a model to describe methods that we have used to generate soluble protein that is purified in an active form with both cobalamin and [4Fe-4S] cluster cofactors bound. Additionally, we highlight the methods that we developed to characterize the enzyme following purification.
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30
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Cho SH, Kim SY, Tomita T, Shiraishi T, Park JS, Sato S, Kudo F, Eguchi T, Funa N, Nishiyama M, Kuzuyama T. Fosfomycin Biosynthesis via Transient Cytidylylation of 2-Hydroxyethylphosphonate by the Bifunctional Fom1 Enzyme. ACS Chem Biol 2017; 12:2209-2215. [PMID: 28727444 DOI: 10.1021/acschembio.7b00419] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Fosfomycin is a wide-spectrum phosphonate antibiotic that is used clinically to treat cystitis, tympanitis, etc. Its biosynthesis starts with the formation of a carbon-phosphorus bond catalyzed by the phosphoenolpyruvate phosphomutase Fom1. We identified an additional cytidylyltransferase (CyTase) domain at the Fom1 N-terminus in addition to the phosphoenolpyruvate phosphomutase domain at the Fom1 C-terminus. Here, we demonstrate that Fom1 is bifunctional and that the Fom1 CyTase domain catalyzes the cytidylylation of the 2-hydroxyethylphosphonate (HEP) intermediate to produce cytidylyl-HEP. On the basis of this new function of Fom1, we propose a revised fosfomycin biosynthetic pathway that involves the transient CMP-conjugated intermediate. The identification of a biosynthetic mechanism via such transient cytidylylation of a biosynthetic intermediate fundamentally advances the understanding of phosphonate biosynthesis in nature. The crystal structure of the cytidylyl-HEP-bound CyTase domain provides a basis for the substrate specificity and reveals unique catalytic elements not found in other members of the CyTase family.
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Affiliation(s)
- Su-Hee Cho
- Biotechnology
Research Center, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Seung-Young Kim
- Department
of Food Science and Biotechnology, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Takeo Tomita
- Biotechnology
Research Center, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Taro Shiraishi
- Biotechnology
Research Center, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Jin-Soo Park
- Biotechnology
Research Center, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Shusuke Sato
- Department
of Chemistry, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8551, Japan
| | - Fumitaka Kudo
- Department
of Chemistry, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8551, Japan
| | - Tadashi Eguchi
- Department
of Chemistry, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8551, Japan
| | - Nobutaka Funa
- Department
of Food Science and Biotechnology, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Makoto Nishiyama
- Biotechnology
Research Center, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Tomohisa Kuzuyama
- Biotechnology
Research Center, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
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31
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Sato S, Kudo F, Kim SY, Kuzuyama T, Eguchi T. Methylcobalamin-Dependent Radical SAM C-Methyltransferase Fom3 Recognizes Cytidylyl-2-hydroxyethylphosphonate and Catalyzes the Nonstereoselective C-Methylation in Fosfomycin Biosynthesis. Biochemistry 2017; 56:3519-3522. [PMID: 28678474 DOI: 10.1021/acs.biochem.7b00472] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
A methylcobalamin (MeCbl)-dependent radical S-adenosyl-l-methionine (SAM) methyltransferase Fom3 was found to catalyze the C-methylation of cytidylyl-2-hydroxyethylphosphonate (HEP-CMP) to give cytidylyl-2-hydroxypropylphosphonate (HPP-CMP), although it was originally proposed to catalyze the C-methylation of 2-hydroxyethylphosphonate to give 2-hydroxypropylphosphonate in the biosynthesis of a unique C-P bond containing antibiotic fosfomycin in Streptomyces. Unexpectedly, the Fom3 reaction product from HEP-CMP was almost a 1:1 diastereomeric mixture of HPP-CMP, indicating that the C-methylation is not stereoselective. Presumably, only the CMP moiety of HEP-CMP is critical for substrate recognition; on the other hand, the enzyme does not fix the 2-hydroxy group of the substrate and either of the prochiral hydrogen atoms at the C2 position can be abstracted by the 5'-deoxyadenosyl radical generated from SAM to form the substrate radical intermediates, which react with MeCbl to afford the corresponding products. This strict substrate recognition mechanism with no stereoselectivity of a MeCbl-dependent radical SAM methyltransferase is remarkable in natural product biosynthetic chemistry, because such a hidden clue for selective substrate recognition is likely to be found in the other biosynthetic pathways.
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Affiliation(s)
- Shusuke Sato
- Department of Chemistry, Tokyo Institute of Technology , 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8551, Japan
| | - Fumitaka Kudo
- Department of Chemistry, Tokyo Institute of Technology , 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8551, Japan
| | - Seung-Young Kim
- Biotechnology Research Center, The University of Tokyo , 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Tomohisa Kuzuyama
- Biotechnology Research Center, The University of Tokyo , 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Tadashi Eguchi
- Department of Chemistry, Tokyo Institute of Technology , 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8551, Japan
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32
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Mahanta N, Zhang Z, Hudson GA, van der Donk WA, Mitchell DA. Reconstitution and Substrate Specificity of the Radical S-Adenosyl-methionine Thiazole C-Methyltransferase in Thiomuracin Biosynthesis. J Am Chem Soc 2017; 139:4310-4313. [PMID: 28301141 PMCID: PMC5477235 DOI: 10.1021/jacs.7b00693] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Thiomuracin is a thiopeptide antibiotic with potent activity toward Gram-positive drug-resistant bacteria. Thiomuracin is biosynthesized from a precursor peptide, TbtA, by a complex array of posttranslational modifications. One of several intriguing transformations is the C-methylation of thiazole, occurring at an unactivated sp2 carbon. Herein, we report the in vitro reconstitution of TbtI, the responsible radical S-adenosyl-methionine (rSAM) C-methyltransferase, which catalyzes the formation of 5-methylthiazole at a single site. Our studies demonstrate that a linear hexazole-bearing intermediate of TbtA is a substrate for TbtI whereas macrocyclized thiomuracin GZ is not. In determining the minimal substrate for TbtI, we found that the enzyme is functional when most of the leader peptide has been removed. The in vitro reconstitution of TbtI, a class C rSAM methyltransferase, further adds to the chemical versatility of rSAM enzymes, and informs on the complexity of thiomuracin biosynthesis.
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Affiliation(s)
- Nilkamal Mahanta
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA
- Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, 1206 West Gregory Drive, Urbana, Illinois 61801, USA
| | - Zhengan Zhang
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA
| | - Graham A. Hudson
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA
| | - Wilfred A. van der Donk
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA
- Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, 1206 West Gregory Drive, Urbana, Illinois 61801, USA
- Howard Hughes Medical Institute, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA
| | - Douglas A. Mitchell
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA
- Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, 1206 West Gregory Drive, Urbana, Illinois 61801, USA
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33
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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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34
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Olivares P, Ulrich EC, Chekan JR, van der Donk WA, Nair SK. Characterization of Two Late-Stage Enzymes Involved in Fosfomycin Biosynthesis in Pseudomonads. ACS Chem Biol 2017; 12:456-463. [PMID: 27977135 DOI: 10.1021/acschembio.6b00939] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The broad-spectrum phosphonate antibiotic fosfomycin is currently in use for clinical treatment of infections caused by both Gram-positive and Gram-negative uropathogens. The antibiotic is biosynthesized by various streptomycetes, as well as by pseudomonads. Notably, the biosynthetic strategies used by the two genera share only two steps: the first step in which primary metabolite phosphoenolpyruvate (PEP) is converted to phosphonopyruvate (PnPy) and the terminal step in which 2-hydroxypropylphosphonate (2-HPP) is converted to fosfomycin. Otherwise, distinct enzymatic paths are employed. Here, we biochemically confirm the last two steps in the fosfomycin biosynthetic pathway of Pseudomonas syringae PB-5123, showing that Psf3 performs the reduction of 2-oxopropylphosphonate (2-OPP) to (S)-2-HPP, followed by the Psf4-catalyzed epoxidation of (S)-2-HPP to fosfomycin. Psf4 can also accept (R)-2-HPP as a substrate but instead performs an oxidation to make 2-OPP. We show that the combined activities of Psf3 and Psf4 can be used to convert racemic 2-HPP to fosfomycin in an enantioconvergent process. X-ray structures of each enzyme with bound substrates provide insights into the stereospecificity of each conversion. These studies shed light on the reaction mechanisms of the two terminal enzymes in a distinct pathway employed by pseudomonads for the production of a potent antimicrobial agent.
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Affiliation(s)
- Philip Olivares
- Department
of Biochemistry, ‡Department of Chemistry, §Carl R. Woese Institute for Genomic
Biology, ∥Howard Hughes Medical Institute, and ⊥Center for Biophysics and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Emily C. Ulrich
- Department
of Biochemistry, ‡Department of Chemistry, §Carl R. Woese Institute for Genomic
Biology, ∥Howard Hughes Medical Institute, and ⊥Center for Biophysics and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Jonathan R. Chekan
- Department
of Biochemistry, ‡Department of Chemistry, §Carl R. Woese Institute for Genomic
Biology, ∥Howard Hughes Medical Institute, and ⊥Center for Biophysics and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Wilfred A. van der Donk
- Department
of Biochemistry, ‡Department of Chemistry, §Carl R. Woese Institute for Genomic
Biology, ∥Howard Hughes Medical Institute, and ⊥Center for Biophysics and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Satish K. Nair
- Department
of Biochemistry, ‡Department of Chemistry, §Carl R. Woese Institute for Genomic
Biology, ∥Howard Hughes Medical Institute, and ⊥Center for Biophysics and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
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35
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Wang Y, Schnell B, Baumann S, Müller R, Begley TP. Biosynthesis of Branched Alkoxy Groups: Iterative Methyl Group Alkylation by a Cobalamin-Dependent Radical SAM Enzyme. J Am Chem Soc 2017; 139:1742-1745. [PMID: 28040895 PMCID: PMC6078419 DOI: 10.1021/jacs.6b10901] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The biosynthesis of branched alkoxy groups, such as the unique t-butyl group found in a variety of natural products, is still poorly understood. Recently, cystobactamids were isolated and identified from Cystobacter sp as novel antibacterials. These metabolites contain an isopropyl group proposed to be formed using CysS, a cobalamin-dependent radical S-adenosylmethionine (SAM) methyltransferase. Here, we reconstitute the CysS-catalyzed reaction, on p-aminobenzoate thioester substrates, and demonstrate that it not only catalyzes sequential methylations of a methyl group to form ethyl and isopropyl groups but remarkably also sec-butyl and t-butyl groups. To our knowledge, this is the first in vitro reconstitution of a cobalamin-dependent radical SAM enzyme catalyzing the conversion of a methyl group to a t-butyl group.
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Affiliation(s)
- Yuanyou Wang
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - Bastien Schnell
- Department of Microbial Natural Products, Helmholtz Institute for Pharmaceutical Research Saarland, Helmholtz Center for Infection Research, Saarland University, Universitätscampus E8.1, D-66123 Saarbrücken, Germany
| | - Sascha Baumann
- Department of Microbial Natural Products, Helmholtz Institute for Pharmaceutical Research Saarland, Helmholtz Center for Infection Research, Saarland University, Universitätscampus E8.1, D-66123 Saarbrücken, Germany
| | - Rolf Müller
- Department of Microbial Natural Products, Helmholtz Institute for Pharmaceutical Research Saarland, Helmholtz Center for Infection Research, Saarland University, Universitätscampus E8.1, D-66123 Saarbrücken, Germany
| | - Tadhg P. Begley
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
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36
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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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37
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Parent A, Guillot A, Benjdia A, Chartier G, Leprince J, Berteau O. The B 12-Radical SAM Enzyme PoyC Catalyzes Valine C β-Methylation during Polytheonamide Biosynthesis. J Am Chem Soc 2016; 138:15515-15518. [PMID: 27934015 PMCID: PMC5410653 DOI: 10.1021/jacs.6b06697] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
![]()
Genomic and metagenomic
investigations have recently led to the
delineation of a novel class of natural products called ribosomally
synthesized and post-translationally modified peptides (RiPPs). RiPPs
are ubiquitous among living organisms and include pharmaceutically
relevant compounds such as antibiotics and toxins. A prominent example
is polytheonamide A, which exhibits numerous post-translational modifications,
some of which were unknown in ribosomal peptides until recently. Among
these post-translational modifications, C-methylations have been proposed
to be catalyzed by two putative radical S-adenosylmethionine
(rSAM) enzymes, PoyB and PoyC. Here we report the in vitro activity of PoyC, the first B12-dependent rSAM enzyme
catalyzing peptide Cβ-methylation. We show that PoyC
catalyzes the formation of S-adenosylhomocysteine
and 5′-deoxyadenosine and the transfer of a methyl group to l-valine residue. In addition, we demonstrate for the first
time that B12-rSAM enzymes have a tightly bound MeCbl cofactor
that during catalysis transfers a methyl group originating from S-adenosyl-l-methionine. Collectively, our results
shed new light on polytheonamide biosynthesis and the large and emerging
family of B12-rSAM enzymes.
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Affiliation(s)
- Aubérie Parent
- Micalis Institute, ChemSyBio, INRA, AgroParisTech, Université Paris-Saclay , F-78350 Jouy-en-Josas, France
| | - Alain Guillot
- Micalis Institute, ChemSyBio, INRA, AgroParisTech, Université Paris-Saclay , F-78350 Jouy-en-Josas, France
| | - Alhosna Benjdia
- Micalis Institute, ChemSyBio, INRA, AgroParisTech, Université Paris-Saclay , F-78350 Jouy-en-Josas, France
| | - Gwladys Chartier
- Micalis Institute, ChemSyBio, INRA, AgroParisTech, Université Paris-Saclay , F-78350 Jouy-en-Josas, France
| | - Jérôme Leprince
- INSERM U982, Université Rouen-Normandie , F-76821 Mont-Saint-Aignan, France
| | - Olivier Berteau
- Micalis Institute, ChemSyBio, INRA, AgroParisTech, Université Paris-Saclay , F-78350 Jouy-en-Josas, France
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38
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Abstract
Organophosphonic acids are unique as natural products in terms of stability and mimicry. The C-P bond that defines these compounds resists hydrolytic cleavage, while the phosphonyl group is a versatile mimic of transition-states, intermediates, and primary metabolites. This versatility may explain why a variety of organisms have extensively explored the use organophosphonic acids as bioactive secondary metabolites. Several of these compounds, such as fosfomycin and bialaphos, figure prominently in human health and agriculture. The enzyme reactions that create these molecules are an interesting mix of chemistry that has been adopted from primary metabolism as well as those with no chemical precedent. Additionally, the phosphonate moiety represents a source of inorganic phosphate to microorganisms that live in environments that lack this nutrient; thus, unusual enzyme reactions have also evolved to cleave the C-P bond. This review is a comprehensive summary of the occurrence and function of organophosphonic acids natural products along with the mechanisms of the enzymes that synthesize and catabolize these molecules.
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Affiliation(s)
- Geoff P Horsman
- Department of Chemistry and Biochemistry, Wilfrid Laurier University , Waterloo, Ontario N2L 3C5, Canada
| | - David L Zechel
- Department of Chemistry, Queen's University , Kingston, Ontario K7L 3N6, Canada
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39
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Mechanistic insights into class B radical-S-adenosylmethionine methylases: ubiquitous tailoring enzymes in natural product biosynthesis. Curr Opin Chem Biol 2016; 35:73-79. [PMID: 27632683 DOI: 10.1016/j.cbpa.2016.08.021] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2016] [Accepted: 08/23/2016] [Indexed: 01/06/2023]
Abstract
Class B radical S-adenosylmethionine (SAM) methylases are notable for their ability to catalyse methylation reactions in the biosynthesis of a wide variety of natural products, including polyketides, ribosomally biosynthesised and post-translationally modified peptides (RiPPs), nonribosomal peptides (NRPs), aminoglycosides, β-lactams, phosphonates, enediynes, aminocoumarins and terpenes. Here, we discuss the diversity of substrates and catalytic mechanism utilised by such enzymes, highlighting the stereochemical course of methylation reactions at un-activated carbon centres and the ability of some members of the family to catalyse multiple methylations.
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40
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Busche T, Winkler A, Wedderhoff I, Rückert C, Kalinowski J, Ortiz de Orué Lucana D. Deciphering the Transcriptional Response Mediated by the Redox-Sensing System HbpS-SenS-SenR from Streptomycetes. PLoS One 2016; 11:e0159873. [PMID: 27541358 PMCID: PMC4991794 DOI: 10.1371/journal.pone.0159873] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2016] [Accepted: 07/08/2016] [Indexed: 12/30/2022] Open
Abstract
The secreted protein HbpS, the membrane-embedded sensor kinase SenS and the cytoplasmic response regulator SenR from streptomycetes have been shown to form a novel type of signaling pathway. Based on structural biology as well as different biochemical and biophysical approaches, redox stress-based post-translational modifications in the three proteins were shown to modulate the activity of this signaling pathway. In this study, we show that the homologous system, named here HbpSc-SenSc-SenRc, from the model species Streptomyces coelicolor A3(2) provides this bacterium with an efficient defense mechanism under conditions of oxidative stress. Comparative analyses of the transcriptomes of the Streptomyces coelicolor A3(2) wild-type and the generated hbpSc-senSc-senRc mutant under native and oxidative-stressing conditions allowed to identify differentially expressed genes, whose products may enhance the anti-oxidative defense of the bacterium. Amongst others, the results show an up-regulated transcription of genes for biosynthesis of cysteine and vitamin B12, transport of methionine and vitamin B12, and DNA synthesis and repair. Simultaneously, transcription of genes for degradation of an anti-oxidant compound is down-regulated in a HbpSc-SenSc-SenRc-dependent manner. It appears that HbpSc-SenSc-SenRc controls the non-enzymatic response of Streptomyces coelicolor A3(2) to counteract the hazardous effects of oxidative stress. Binding of the response regulator SenRc to regulatory regions of some of the studied genes indicates that the regulation is direct. The results additionally suggest that HbpSc-SenSc-SenRc may act in concert with other regulatory modules such as a transcriptional regulator, a two-component system and the Streptomyces B12 riboswitch. The transcriptomics data, together with our previous in vitro results, enable a profound characterization of the HbpS-SenS-SenR system from streptomycetes. Since homologues to HbpS-SenS-SenR are widespread in different actinobacteria with ecological and medical relevance, the data presented here will serve as a basis to elucidate the biological role of these homologues.
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Affiliation(s)
- Tobias Busche
- Microbial Genomics and Biotechnology, Center for Biotechnology, Bielefeld University, Universitätsstraße 27, 33615, Bielefeld, Germany
| | - Anika Winkler
- Microbial Genomics and Biotechnology, Center for Biotechnology, Bielefeld University, Universitätsstraße 27, 33615, Bielefeld, Germany
| | - Ina Wedderhoff
- Applied Genetics of Microorganisms, Department of Biology and Chemistry, University of Osnabrueck, Osnabrueck, Barbarastraße 13, 49076, Osnabrueck, Germany
| | - Christian Rückert
- Microbial Genomics and Biotechnology, Center for Biotechnology, Bielefeld University, Universitätsstraße 27, 33615, Bielefeld, Germany
| | - Jörn Kalinowski
- Microbial Genomics and Biotechnology, Center for Biotechnology, Bielefeld University, Universitätsstraße 27, 33615, Bielefeld, Germany
| | - Darío Ortiz de Orué Lucana
- Applied Genetics of Microorganisms, Department of Biology and Chemistry, University of Osnabrueck, Osnabrueck, Barbarastraße 13, 49076, Osnabrueck, Germany
- * E-mail:
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Ding W, Li Q, Jia Y, Ji X, Qianzhu H, Zhang Q. Emerging Diversity of the Cobalamin-Dependent Methyltransferases Involving Radical-Based Mechanisms. Chembiochem 2016; 17:1191-7. [PMID: 27028019 DOI: 10.1002/cbic.201600107] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2016] [Indexed: 11/10/2022]
Abstract
Cobalamins comprise a group of cobalt-containing organometallic cofactors that play important roles in cellular metabolism. Although many cobalamin-dependent methyltransferases (e.g., methionine synthase MetH) have been extensively studied, a new group of methyltransferases that are cobalamin-dependent and utilize radical chemistry in catalysis is just beginning to be appreciated. In this Concept article, we summarize recent advances in the understanding of the radical-based and cobalamin-dependent methyltransferases and discuss the functional and mechanistic diversity of this emerging class of enzymes.
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Affiliation(s)
- Wei Ding
- Key Laboratory of Cell Activities and Stress Adaptations, (Ministry of Education), School of Life Sciences, Lanzhou University, Lanzhou, 730000, China.,Department of Chemistry, Fudan University, Shanghai, 200433, China
| | - Qien Li
- Key Laboratory of Cell Activities and Stress Adaptations, (Ministry of Education), School of Life Sciences, Lanzhou University, Lanzhou, 730000, China
| | - Youli Jia
- Key Laboratory of Cell Activities and Stress Adaptations, (Ministry of Education), School of Life Sciences, Lanzhou University, Lanzhou, 730000, China.,Department of Chemistry, Fudan University, Shanghai, 200433, China
| | - Xinjian Ji
- Department of Chemistry, Fudan University, Shanghai, 200433, China
| | - Haocheng Qianzhu
- Department of Chemistry, Fudan University, Shanghai, 200433, China
| | - Qi Zhang
- Department of Chemistry, Fudan University, Shanghai, 200433, China.
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Blaszczyk AJ, Silakov A, Zhang B, Maiocco SJ, Lanz ND, Kelly WL, Elliott SJ, Krebs C, Booker SJ. Spectroscopic and Electrochemical Characterization of the Iron-Sulfur and Cobalamin Cofactors of TsrM, an Unusual Radical S-Adenosylmethionine Methylase. J Am Chem Soc 2016; 138:3416-26. [PMID: 26841310 DOI: 10.1021/jacs.5b12592] [Citation(s) in RCA: 68] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
TsrM, an annotated radical S-adenosylmethionine (SAM) enzyme, catalyzes the methylation of carbon 2 of the indole ring of L-tryptophan. Its reaction is the first step in the biosynthesis of the unique quinaldic acid moiety of thiostrepton A, a thiopeptide antibiotic. The appended methyl group derives from SAM; however, the enzyme also requires cobalamin and iron-sulfur cluster cofactors for turnover. In this work we report the overproduction and purification of TsrM and the characterization of its metallocofactors by UV-visible, electron paramagnetic resonance, hyperfine sublevel correlation (HYSCORE), and Mössbauer spectroscopies as well as protein-film electrochemistry (PFE). The enzyme contains 1 equiv of its cobalamin cofactor in its as-isolated state and can be reconstituted with iron and sulfide to contain one [4Fe-4S] cluster with a site-differentiated Fe(2+)/Fe(3+) pair. Our spectroscopic studies suggest that TsrM binds cobalamin in an uncharacteristic five-coordinate base-off/His-off conformation, whereby the dimethylbenzimidazole group is replaced by a non-nitrogenous ligand, which is likely a water molecule. Electrochemical analysis of the protein by PFE indicates a one-electron redox feature with a midpoint potential of -550 mV, which is assigned to a [4Fe-4S](2+)/[4Fe-4S](+) redox couple. Analysis of TsrM by Mössbauer and HYSCORE spectroscopies suggests that SAM does not bind to the unique iron site of the cluster in the same manner as in other radical SAM (RS) enzymes, yet its binding still perturbs the electronic configuration of both the Fe/S cluster and the cob(II)alamin cofactors. These biophysical studies suggest that TsrM is an atypical RS enzyme, consistent with its reported inability to catalyze formation of a 5'-deoxyadenosyl 5'-radical.
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Affiliation(s)
| | | | | | - Stephanie J Maiocco
- Department of Chemistry, Boston University , 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States
| | | | - Wendy L Kelly
- School of Chemistry and Biochemistry and the Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology , Atlanta, Georgia 30332, United States
| | - Sean J Elliott
- Department of Chemistry, Boston University , 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States
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Consecutive radical S-adenosylmethionine methylations form the ethyl side chain in thienamycin biosynthesis. Proc Natl Acad Sci U S A 2015; 112:10354-8. [PMID: 26240322 DOI: 10.1073/pnas.1508615112] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Despite their broad anti-infective utility, the biosynthesis of the paradigm carbapenem antibiotic, thienamycin, remains largely unknown. Apart from the first two steps shared with a simple carbapenem, the pathway sharply diverges to the more structurally complex members of this class of β-lactam antibiotics, such as thienamycin. Existing evidence points to three putative cobalamin-dependent radical S-adenosylmethionine (RS) enzymes, ThnK, ThnL, and ThnP, as potentially being responsible for assembly of the ethyl side chain at C6, bridgehead epimerization at C5, installation of the C2-thioether side chain, and C2/3 desaturation. The C2 substituent has been demonstrated to be derived by stepwise truncation of CoA, but the timing of these events with respect to C2-S bond formation is not known. We show that ThnK of the three apparent cobalamin-dependent RS enzymes performs sequential methylations to build out the C6-ethyl side chain in a stereocontrolled manner. This enzymatic reaction was found to produce expected RS methylase coproducts S-adenosylhomocysteine and 5'-deoxyadenosine, and to require cobalamin. For double methylation to occur, the carbapenam substrate must bear a CoA-derived C2-thioether side chain, implying the activity of a previous sulfur insertion by an as-yet unidentified enzyme. These insights allow refinement of the central steps in complex carbapenem biosynthesis.
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Bauerle MR, Schwalm EL, Booker SJ. Mechanistic diversity of radical S-adenosylmethionine (SAM)-dependent methylation. J Biol Chem 2015; 290:3995-4002. [PMID: 25477520 PMCID: PMC4326810 DOI: 10.1074/jbc.r114.607044] [Citation(s) in RCA: 179] [Impact Index Per Article: 19.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Radical S-adenosylmethionine (SAM) enzymes use the oxidizing power of a 5'-deoxyadenosyl 5'-radical to initiate an amazing array of transformations, usually through the abstraction of a target substrate hydrogen atom. A common reaction of radical SAM (RS) enzymes is the methylation of unactivated carbon or phosphorous atoms found in numerous primary and secondary metabolites, as well as in proteins, sugars, lipids, and RNA. However, neither the chemical mechanisms by which these unactivated atoms obtain methyl groups nor the actual methyl donors are conserved. In fact, RS methylases have been grouped into three classes based on protein architecture, cofactor requirement, and predicted mechanism of catalysis. Class A methylases use two cysteine residues to methylate sp(2)-hybridized carbon centers. Class B methylases require a cobalamin cofactor to methylate both sp(2)-hybridized and sp(3)-hybridized carbon centers as well as phosphinate phosphorous atoms. Class C methylases share significant sequence homology with the RS enzyme, HemN, and may bind two SAM molecules simultaneously to methylate sp(2)-hybridized carbon centers. Lastly, we describe a new class of recently discovered RS methylases. These Class D methylases, unlike Class A, B, and C enzymes, which use SAM as the source of the donated methyl carbon, are proposed to methylate sp(2)-hybridized carbon centers using methylenetetrahydrofolate as the source of the appended methyl carbon.
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Affiliation(s)
- Matthew R Bauerle
- From the Department of Chemistry and the Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, 16802
| | - Erica L Schwalm
- From the Department of Chemistry and the Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, 16802
| | - Squire J Booker
- From the Department of Chemistry and the Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, 16802
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Ortiz de Orué Lucana D, Fedosov SN, Wedderhoff I, Che EN, Torda AE. The extracellular heme-binding protein HbpS from the soil bacterium Streptomyces reticuli is an aquo-cobalamin binder. J Biol Chem 2014; 289:34214-28. [PMID: 25342754 PMCID: PMC4256353 DOI: 10.1074/jbc.m114.585489] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2014] [Revised: 10/22/2014] [Indexed: 11/06/2022] Open
Abstract
The extracellular protein HbpS from Streptomyces reticuli interacts with iron ions and heme. It also acts in concert with the two-component sensing system SenS-SenR in response to oxidative stress. Sequence comparisons suggested that the protein may bind a cobalamin. UV-visible spectroscopy confirmed binding (Kd = 34 μm) to aquo-cobalamin (H2OCbl(+)) but not to other cobalamins. Competition experiments with the H2OCbl(+)-coordinating ligand CN(-) and comparison of mutants identified a histidine residue (His-156) that coordinates the cobalt ion of H2OCbl(+) and substitutes for water. HbpS·Cobalamin lacks the Asp-X-His-X-X-Gly motif seen in some cobalamin binding enzymes. Preliminary tests showed that a related HbpS protein from a different species also binds H2OCbl(+). Furthermore, analyses of HbpS-heme binding kinetics are consistent with the role of HbpS as a heme-sensor and suggested a role in heme transport. Given the high occurrence of HbpS-like sequences among Gram-positive and Gram-negative bacteria, our findings suggest a great functional versatility among these proteins.
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Affiliation(s)
- Darío Ortiz de Orué Lucana
- From the Applied Genetics of Microorganisms, Department of Biology/Chemistry, University of Osnabrueck, 49067 Osnabrueck, Germany,
| | - Sergey N Fedosov
- Department of Engineering, Aarhus University, 8000 Aarhus, Denmark, and
| | - Ina Wedderhoff
- From the Applied Genetics of Microorganisms, Department of Biology/Chemistry, University of Osnabrueck, 49067 Osnabrueck, Germany
| | - Edith N Che
- From the Applied Genetics of Microorganisms, Department of Biology/Chemistry, University of Osnabrueck, 49067 Osnabrueck, Germany
| | - Andrew E Torda
- Centre for Bioinformatics, Hamburg University, 20146 Hamburg, Germany
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Allen KD, Wang SC. Spectroscopic characterization and mechanistic investigation of P-methyl transfer by a radical SAM enzyme from the marine bacterium Shewanella denitrificans OS217. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2014; 1844:2135-44. [PMID: 25224746 DOI: 10.1016/j.bbapap.2014.09.009] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2014] [Revised: 09/05/2014] [Accepted: 09/07/2014] [Indexed: 10/24/2022]
Abstract
Natural products containing carbon-phosphorus bonds elicit important bioactivity in many organisms. l-Phosphinothricin contains the only known naturally-occurring carbon-phosphorus-carbon bond linkage. In actinomycetes, the cobalamin-dependent radical S-adenosyl-l-methionine (SAM) methyltransferase PhpK catalyzes the formation of the second C-P bond to generate the complete C-P-C linkage in phosphinothricin. Here we use electron paramagnetic resonance and nuclear magnetic resonance spectroscopies to characterize and demonstrate the activity of a cobalamin-dependent radical SAM methyltransferase denoted SD_1168 from Shewanella denitrificans OS217, a marine bacterium that has not been reported to synthesize phosphinothricin. Recombinant, refolded, and reconstituted SD_1168 binds a four-iron, four-sulfur cluster that interacts with SAM and cobalamin. In the presence of SAM, a reductant, and methylcobalamin, SD_1168 surprisingly catalyzes the P-methylation of N-acetyl-demethylphosphinothricin and demethylphosphinothricin to produce N-acetyl-phosphinothricin and phosphinothricin, respectively. In addition, this enzyme is active in the absence of methylcobalamin if the strong reductant titanium (III) citrate and hydroxocobalamin are provided. When incubated with [methyl-(13)C] cobalamin and titanium citrate, both [methyl-(13)C] and unlabeled N-acetylphosphinothricin are produced. Our results suggest that SD_1168 catalyzes P-methylation using radical SAM-dependent chemistry with cobalamin as a coenzyme. In light of recent genomic information, the discovery of this P-methyltransferase suggests that S. denitrificans produces a phosphinate natural product.
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Affiliation(s)
- Kylie D Allen
- School of Molecular Biosciences, College of Veterinary Medicine, PO Box 647520, Washington State University, Pullman, WA 99164-7520, USA.
| | - Susan C Wang
- School of Molecular Biosciences, College of Veterinary Medicine, PO Box 647520, Washington State University, Pullman, WA 99164-7520, USA.
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Identification of a unique radical S-adenosylmethionine methylase likely involved in methanopterin biosynthesis in Methanocaldococcus jannaschii. J Bacteriol 2014; 196:3315-23. [PMID: 25002541 DOI: 10.1128/jb.01903-14] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Methanopterin (MPT) and its analogs are coenzymes required for methanogenesis and methylotrophy in specialized microorganisms. The methyl groups at C-7 and C-9 of the pterin ring distinguish MPT from all other pterin-containing natural products. However, the enzyme(s) responsible for the addition of these methyl groups has yet to be identified. Here we demonstrate that a putative radical S-adenosyl-L-methionine (SAM) enzyme superfamily member encoded by the MJ0619 gene in the methanogen Methanocaldococcus jannaschii is likely this missing methylase. When MJ0619 was heterologously expressed in Escherichia coli, various methylated pterins were detected, consistent with MJ0619 catalyzing methylation at C-7 and C-9 of 7,8-dihydro-6-hydroxymethylpterin, a common intermediate in both folate and MPT biosynthesis. Site-directed mutagenesis of Cys77 present in the first of two canonical radical SAM CX₃CX₂C motifs present in MJ0619 did not inhibit C-7 methylation, while mutation of Cys102, found in the other radical SAM amino acid motif, resulted in the loss of C-7 methylation, suggesting that the first motif could be involved in C-9 methylation, while the second motif is required for C-7 methylation. Further experiments demonstrated that the C-7 methyl group is not derived from methionine and that methylation does not require cobalamin. When E. coli cells expressing MJ0619 were grown with deuterium-labeled acetate as the sole carbon source, the resulting methyl group on the pterin was predominantly labeled with three deuteriums. Based on these results, we propose that this archaeal radical SAM methylase employs a previously uncharacterized mechanism for methylation, using methylenetetrahydrofolate as a methyl group donor.
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