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Gao Y, Zhu Y, Awakawa T, Abe I. Unusual cysteine modifications in natural product biosynthesis. RSC Chem Biol 2024; 5:293-311. [PMID: 38576726 PMCID: PMC10989515 DOI: 10.1039/d4cb00020j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2024] [Accepted: 02/08/2024] [Indexed: 04/06/2024] Open
Abstract
l-Cysteine is a highly reactive amino acid that is modified into a variety of chemical structures, including cysteine sulfinic acid in human metabolic pathways, and sulfur-containing scaffolds of amino acids, alkaloids, and peptides in natural product biosynthesis. Among the modification enzymes responsible for these cysteine-derived compounds, metalloenzymes constitute an important family of enzymes that catalyze a wide variety of reactions. Therefore, understanding their reaction mechanisms is important for the biosynthetic production of cysteine-derived natural products. This review mainly summarizes recent mechanistic investigations of metalloenzymes, with a particular focus on recently discovered mononuclear non-heme iron (NHI) enzymes, dinuclear NHI enzymes, and radical-SAM enzymes involved in unusual cysteine modifications in natural product biosynthesis.
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Affiliation(s)
- Yaojie Gao
- Graduate School of Pharmaceutical Sciences, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku Tokyo 113-0033 Japan
| | - Yuhao Zhu
- Graduate School of Pharmaceutical Sciences, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku Tokyo 113-0033 Japan
| | - Takayoshi Awakawa
- Graduate School of Pharmaceutical Sciences, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku Tokyo 113-0033 Japan
- RIKEN Center for Sustainable Resource Science Wako Saitama 351-0198 Japan
| | - Ikuro Abe
- Graduate School of Pharmaceutical Sciences, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku Tokyo 113-0033 Japan
- Collaborative Research Institute for Innovative Microbiology, The University of Tokyo Yayoi 1-1-1, Bunkyo-ku Tokyo 113-8657 Japan
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2
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Ma B, Britt RD, Tao L. Radical SAM Enzyme PylB Generates a Lysyl Radical Intermediate in the Biosynthesis of Pyrrolysine by Using SAM as a Cofactor. J Am Chem Soc 2024; 146:6544-6556. [PMID: 38426740 DOI: 10.1021/jacs.3c11266] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/02/2024]
Abstract
Pyrrolysine, the 22nd amino acid encoded by the natural genetic code, is essential for methanogenic archaea to catabolize methylamines into methane. The structure of pyrrolysine consists of a methylated pyrroline carboxylate that is linked to the ε-amino group of the l-lysine via an amide bond. The biosynthesis of pyrrolysine requires three enzymes: PylB, PylC, and PylD. PylB is a radical S-adenosyl-l-methionine (SAM) enzyme and catalyzes the first biosynthetic step, the isomerization of l-lysine into methylornithine. PylC catalyzes an ATP-dependent ligation of methylornithine and a second l-lysine to form l-lysine-Nε-methylornithine. The last biosynthetic step is catalyzed by PylD via oxidation of the PylC product to form pyrrolysine. While enzymatic reactions of PylC and PylD have been well characterized by X-ray crystallography and in vitro studies, mechanistic understanding of PylB is still relatively limited. Here, we report the first in vitro activity of PylB to form methylornithine via the isomerization of l-lysine. We also identify a lysyl C4 radical intermediate that is trapped, with its electronic structure and geometric structure well characterized by EPR and ENDOR spectroscopy. In addition, we demonstrate that SAM functions as a catalytic cofactor in PylB catalysis rather than canonically as a cosubstrate. This work provides detailed mechanistic evidence for elucidating the carbon backbone rearrangement reaction catalyzed by PylB during the biosynthesis of pyrrolysine.
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Affiliation(s)
- Baixu Ma
- Department of Chemistry, Southern University of Science and Technology, Shenzhen 518055, China
| | - R David Britt
- Department of Chemistry, University of California, Davis, Davis, California 95616, United States
| | - Lizhi Tao
- Department of Chemistry, Southern University of Science and Technology, Shenzhen 518055, China
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3
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Price NPJ, Jackson MA, Hartman TM, Bannantine JP, Naumann TA, Vermillion KE, Koch AA, Kennedy PD. Precursor-Directed Biosynthesis and Biological Testing of omega-Alicyclic- and neo-Branched Tunicamycin N-Acyl Variants. ACS Chem Biol 2023; 18:2267-2280. [PMID: 37788216 DOI: 10.1021/acschembio.3c00324] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/05/2023]
Abstract
Tunicamycins (TUNs) are Streptomyces-derived natural products, widely used to block protein N-glycosylation in eukaryotes or cell wall biosynthesis in bacteria. Modified or synthetic TUN analogues that uncouple these activities have considerable potential as novel mode-of-action antibacterial agents. Chemically modified TUNs reported previously with attenuated activity on yeast have pinpointed eukaryotic-specific chemophores in the uridyl group and the N-acyl chain length and terminal branching pattern. A small molecule screen of fatty acid biosynthetic primers identified several novel alicyclic- and neo-branched TUN N-acyl variants, with primer incorporation at the terminal omega-acyl position. TUNs with unique 5- and 6-carbon ω-cycloalkane and ω-cycloalkene acyl chains are produced under fermentation and in yields comparable with the native TUN. The purification, structural assignments, and the comparable antimicrobial properties of 15 of these compounds are reported, greatly extending the structural diversity of this class of compounds for potential medicinal and agricultural applications.
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Affiliation(s)
- Neil P J Price
- USDA, Agricultural Research Service, National Center for Agricultural Utilization Research, Renewable Product Technology Research, 1815 N. University St., Peoria, Illinois 61604, United States
| | - Michael A Jackson
- USDA, Agricultural Research Service, National Center for Agricultural Utilization Research, Renewable Product Technology Research, 1815 N. University St., Peoria, Illinois 61604, United States
| | - Trina M Hartman
- USDA, Agricultural Research Service, National Center for Agricultural Utilization Research, Renewable Product Technology Research, 1815 N. University St., Peoria, Illinois 61604, United States
| | - John P Bannantine
- USDA, Agricultural Research Service, National Animal Disease Center, 1920 Dayton Ave., Ames, Iowa 50010, United States
| | - Todd A Naumann
- USDA, Agricultural Research Service, National Center for Agricultural Utilization Research, Renewable Product Technology Research, 1815 N. University St., Peoria, Illinois 61604, United States
| | - Karl E Vermillion
- USDA, Agricultural Research Service, National Center for Agricultural Utilization Research, Renewable Product Technology Research, 1815 N. University St., Peoria, Illinois 61604, United States
| | - Aaron A Koch
- Cayman Chemical, 1180 E. Ellsworth Rd., Ann Arbor, Michigan 48108, United States
| | - Paul D Kennedy
- Cayman Chemical, 1180 E. Ellsworth Rd., Ann Arbor, Michigan 48108, United States
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4
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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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5
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Abstract
Methyl groups are well understood to play a critical role in pharmaceutical molecules, especially those bearing saturated heterocyclic cores. Accordingly, methods that install methyl groups onto complex molecules are highly coveted. Late-stage C-H functionalization is a particularly attractive approach, allowing chemists to bypass lengthy syntheses and facilitating the expedited synthesis of drug analogues. Herein, we disclose the direct introduction of methyl groups via C(sp3)-H functionalization of a broad array of saturated heterocycles, enabled by the merger of decatungstate photocatalysis and a unique nickel-mediated SH2 bond formation. To further demonstrate its synthetic utility as a tool for late-stage functionalization, this method was applied to a range of drug molecules en route to an array of methylated drug analogues.
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Affiliation(s)
- Edna Mao
- Merck Center for Catalysis at Princeton University, Princeton, New Jersey 08544, United States
| | - David W C MacMillan
- Merck Center for Catalysis at Princeton University, Princeton, New Jersey 08544, United States
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6
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Deng WH, Liao RZ. Sequential C-H Methylation Catalyzed by the B 12 -Dependent SAM Enzyme TokK: Comprehensive Theoretical Study of Selectivities. Chemistry 2023; 29:e202202995. [PMID: 36321632 DOI: 10.1002/chem.202202995] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2022] [Revised: 10/31/2022] [Accepted: 11/02/2022] [Indexed: 12/14/2022]
Abstract
TokK is a B12 -dependent radical SAM enzyme involved in the biosynthesis of the β-lactam antibiotic asparenomycin A. It can catalyze three methylations on different sp3 -hybridized carbon positions to introduce an isopropyl side chain at the β-lactam ring of pantetheinylated carbapenem. Herein, we report a quantum chemical study of the reaction mechanism of TokK. A stepwise ''push-pull'' radical relay mechanism is proposed for each methylation: a 5'-deoxyadenosine radical first abstracts a hydrogen atom from the substrate in the active site, then methylcobalamin directionally donates a methyl group to the substrate. More importantly, calculations were able to uncover the origin of observed chemoselectivity and stereoselectivity for the first methylation and regioselectivity for the following two methylations. Further detailed distortion/interaction analysis can help to unravel the main factors controlling the selectivities. Our findings of sequential methylations by TokK could have profound implications for studying other B12 -dependent radical SAM enzymes.
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Affiliation(s)
- Wen-Hao Deng
- Key Laboratory of Material Chemistry for Energy Conversion and Storage Ministry of Education Hubei Key Laboratory of Bioinorganic Chemistry and Materia Medica Hubei Key Laboratory of Materials Chemistry and Service Failure School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan, 430074, P. R. China
| | - Rong-Zhen Liao
- Key Laboratory of Material Chemistry for Energy Conversion and Storage Ministry of Education Hubei Key Laboratory of Bioinorganic Chemistry and Materia Medica Hubei Key Laboratory of Materials Chemistry and Service Failure School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan, 430074, P. R. China
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7
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Hu X, Shi Y, Jiang B, Fu J, Li X, Li S, Sun G, Ren W, Hu X, You X, Liu Z, Han X, Zhang T, Hong B, Wu L. Iterative Methylation Leads to 3-Methylchuangxinmycin Production in Actinoplanes tsinanensis CPCC 200056. JOURNAL OF NATURAL PRODUCTS 2023; 86:1-7. [PMID: 36649560 DOI: 10.1021/acs.jnatprod.2c00360] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
A new congener of chuangxinmycin (CM) was identified from Actinoplanes tsinanensis CPCC 200056. Its structure was determined as 3-methylchuangxinmycin (MCM) by 1D and 2D NMR. MCM could be generated in vivo from CM by heterologous expression of the vitamin B12-dependent radical SAM enzyme CxnA/A1 responsible for methylation of 3-demethylchuangxinmycin (DCM) in CM biosynthesis, indicating that CxnA/A1 could perform iterative methylation for MCM production. In vitro assays revealed significant activities of CM, DCM, and MCM against Mycobacterium tuberculosis H37Rv and clinically isolated isoniazid/rifampin-resistant M. tuberculosis, suggesting that CM and its derivatives may have potential for antituberculosis drug development.
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Affiliation(s)
- Xiaomin Hu
- NHC Key Laboratory of Biotechnology of Antibiotics, and CAMS Key Laboratory of Synthetic Biology for Drug Innovation, Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100050, People's Republic of China
| | - Yuanyuan Shi
- NHC Key Laboratory of Biotechnology of Antibiotics, and CAMS Key Laboratory of Synthetic Biology for Drug Innovation, Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100050, People's Republic of China
| | - Bingya Jiang
- NHC Key Laboratory of Biotechnology of Antibiotics, and CAMS Key Laboratory of Synthetic Biology for Drug Innovation, Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100050, People's Republic of China
| | - Jie Fu
- NHC Key Laboratory of Biotechnology of Antibiotics, and CAMS Key Laboratory of Synthetic Biology for Drug Innovation, Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100050, People's Republic of China
| | - Xingxing Li
- NHC Key Laboratory of Biotechnology of Antibiotics, and CAMS Key Laboratory of Synthetic Biology for Drug Innovation, Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100050, People's Republic of China
| | - Shufen Li
- NHC Key Laboratory of Biotechnology of Antibiotics, and CAMS Key Laboratory of Synthetic Biology for Drug Innovation, Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100050, People's Republic of China
| | - Guizhi Sun
- NHC Key Laboratory of Biotechnology of Antibiotics, and CAMS Key Laboratory of Synthetic Biology for Drug Innovation, Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100050, People's Republic of China
| | - Weicong Ren
- NHC Key Laboratory of Biotechnology of Antibiotics, and CAMS Key Laboratory of Synthetic Biology for Drug Innovation, Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100050, People's Republic of China
| | - Xinxin Hu
- NHC Key Laboratory of Biotechnology of Antibiotics, and CAMS Key Laboratory of Synthetic Biology for Drug Innovation, Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100050, People's Republic of China
| | - Xuefu You
- NHC Key Laboratory of Biotechnology of Antibiotics, and CAMS Key Laboratory of Synthetic Biology for Drug Innovation, Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100050, People's Republic of China
| | - Zhiyong Liu
- State Key Laboratory of Respiratory Disease, China-New Zealand Joint Laboratory of Biomedicine and Health, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, People's Republic of China
| | - Xingli Han
- State Key Laboratory of Respiratory Disease, China-New Zealand Joint Laboratory of Biomedicine and Health, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, People's Republic of China
| | - Tianyu Zhang
- State Key Laboratory of Respiratory Disease, China-New Zealand Joint Laboratory of Biomedicine and Health, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, People's Republic of China
| | - Bin Hong
- NHC Key Laboratory of Biotechnology of Antibiotics, and CAMS Key Laboratory of Synthetic Biology for Drug Innovation, Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100050, People's Republic of China
| | - Linzhuan Wu
- NHC Key Laboratory of Biotechnology of Antibiotics, and CAMS Key Laboratory of Synthetic Biology for Drug Innovation, Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100050, People's Republic of China
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Tsymbal AV, Bizzini LD, MacMillan DWC. Nickel Catalysis via S H2 Homolytic Substitution: The Double Decarboxylative Cross-Coupling of Aliphatic Acids. J Am Chem Soc 2022; 144:21278-21286. [PMID: 36375080 PMCID: PMC10680145 DOI: 10.1021/jacs.2c08989] [Citation(s) in RCA: 31] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Cross-coupling platforms are traditionally built around a sequence of closed-shell steps, such as oxidative addition, transmetalation, and reductive elimination. Herein, we describe a dual photo/nickel catalytic manifold that performs cross-coupling via a complementary sequence involving free radical generation, radical sorting via selective binding to a Ni(II) center, and bimolecular homolytic substitution (SH2) at a high-valent nickel-alkyl complex. This catalytic manifold enables the hitherto elusive cross-coupling of diverse aliphatic carboxylic acids to generate valuable C(sp3)-C(sp3)-products. Notably, the powerful SH2 mechanism provides general access to sterically encumbered quaternary carbon centers, addressing a long-standing challenge in fragment coupling chemistry.
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Affiliation(s)
- Artem V Tsymbal
- Merck Center for Catalysis at Princeton University, Princeton, New Jersey 08544, United States
| | - Lorenzo Delarue Bizzini
- Merck Center for Catalysis at Princeton University, Princeton, New Jersey 08544, United States
| | - David W C MacMillan
- Merck Center for Catalysis at Princeton University, Princeton, New Jersey 08544, United States
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9
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Mahanta N, PH K, KS S, Das S, G. D. Recent Advancements in Bottromycin Biosynthesis. Synlett 2022. [DOI: 10.1055/s-0042-1751373] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
AbstractBottromycin is a structurally complex cyclic peptidic compound isolated from Streptomyces bottropensis and related organisms and belongs to the RiPP family of natural products (ribosomally synthesized and post-translationally modified peptides). It exhibits potent antibacterial properties against gram-positive pathogens (including drug resistant strains such as MRSA, MIC 1 μg/mL and VRE, MIC 0.5 μg/mL) and mycoplasma. Bottromycin blocks the binding of the aminoacyl-tRNA to the A-site on the 50S ribosome and hence inhibits protein synthesis. Bottromycins contain structurally diverse post-translational modifications (PTMs) on a small peptide (GPVVVFDC) including a unique macrocyclic amidine, rare β-methylation, terminal thiazole heterocycle, oxidative decarboxylation, and Asp epimerization, among others. It exhibits a precursor peptide organization with a C-terminal follower peptide and a N-terminal core peptide. There are several new studies reported recently which gave detailed insights into the bottromycin biosynthesis pathway. This Account highlights the current advancements in understanding the biosynthetic pathway of bottromycin focusing mainly on the biochemically and structurally characterized enzymes and intricate details of the peptide–protein biophysical interactions. These studies have provided a strong foundation for conducting combinatorial biosynthesis and synthetic biological studies to create novel bottromycin variants for therapeutic applications.1 Introduction2 Biosynthetic Pathway for Bottromycin3 Enzymology of Bottromycin Biosynthesis3.1 Cleavage of Methionine (BotP)3.2 Radical SAM Methyltransferases (BotRMT1, BotRMT2, BotRMT3)3.3 ATP-Dependent YcaO Enzymes3.3.1 Thiazoline Formation by BotC3.3.2 Macrolactamidine Formation by BotCD3.4 Follower Peptide Hydrolysis (BotAH)3.5 Aspartate Epimerization (BotH)3.6 Oxidative Decarboxylation (BotCYP)3.7 O-Methyltransferase (BotOMT)4 Heterologous Bottromycin Production and Analogue Preparation5 Summary and Outlook
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Gagsteiger J, Jahn S, Heidinger L, Gericke L, Andexer JN, Friedrich T, Loenarz C, Layer G. A Cobalamin-Dependent Radical SAM Enzyme Catalyzes the Unique C α -Methylation of Glutamine in Methyl-Coenzyme M Reductase. Angew Chem Int Ed Engl 2022; 61:e202204198. [PMID: 35638156 PMCID: PMC9401015 DOI: 10.1002/anie.202204198] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Indexed: 12/22/2022]
Abstract
Methyl‐coenzyme M reductase, which is responsible for the production of the greenhouse gas methane during biological methane formation, carries several unique posttranslational amino acid modifications, including a 2‐(S)‐methylglutamine. The enzyme responsible for the Cα‐methylation of this glutamine is not known. Herein, we identify and characterize a cobalamin‐dependent radical SAM enzyme as the glutamine C‐methyltransferase. The recombinant protein from Methanoculleus thermophilus binds cobalamin in a base‐off, His‐off conformation and contains a single [4Fe‐4S] cluster. The cobalamin cofactor cycles between the methyl‐cob(III)alamin, cob(II)alamin and cob(I)alamin states during catalysis and produces methylated substrate, 5′‐deoxyadenosine and S‐adenosyl‐l‐homocysteine in a 1 : 1 : 1 ratio. The newly identified glutamine C‐methyltransferase belongs to the class B radical SAM methyltransferases known to catalyze challenging methylation reactions of sp3‐hybridized carbon atoms.
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Affiliation(s)
- Jana Gagsteiger
- Institut für Pharmazeutische Wissenschaften, Pharmazeutische Biologie, Albert-Ludwigs-Universität Freiburg, Stefan-Meier-Str. 19, 79104, Freiburg, Germany
| | - Sören Jahn
- Institut für Pharmazeutische Wissenschaften, Pharmazeutische und Medizinische Chemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 25, 79104, Freiburg, Germany
| | - Lorenz Heidinger
- Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104, Freiburg, Germany
| | - Lukas Gericke
- Institut für Pharmazeutische Wissenschaften, Pharmazeutische und Medizinische Chemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 25, 79104, Freiburg, Germany
| | - Jennifer N Andexer
- Institut für Pharmazeutische Wissenschaften, Pharmazeutische und Medizinische Chemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 25, 79104, Freiburg, Germany
| | - Thorsten Friedrich
- Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104, Freiburg, Germany
| | - Christoph Loenarz
- Institut für Pharmazeutische Wissenschaften, Pharmazeutische und Medizinische Chemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 25, 79104, Freiburg, Germany
| | - Gunhild Layer
- Institut für Pharmazeutische Wissenschaften, Pharmazeutische Biologie, Albert-Ludwigs-Universität Freiburg, Stefan-Meier-Str. 19, 79104, Freiburg, Germany
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11
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Müller M, Germer P, Andexer JN. Biocatalytic One-Carbon Transfer – A Review. SYNTHESIS-STUTTGART 2022. [DOI: 10.1055/s-0040-1719884] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
Abstract
AbstractThis review provides an overview of different C1 building blocks as substrates of enzymes, or part of their cofactors, and the resulting functionalized products. There is an emphasis on the broad range of possibilities of biocatalytic one-carbon extensions with C1 sources of different oxidation states. The identification of uncommon biosynthetic strategies, many of which might serve as templates for synthetic or biotechnological applications, towards one-carbon extensions is supported by recent genomic and metabolomic progress and hence we refer principally to literature spanning from 2014 to 2020.1 Introduction2 Methane, Methanol, and Methylamine3 Glycine4 Nitromethane5 SAM and SAM Ylide6 Other C1 Building Blocks7 Formaldehyde and Glyoxylate as Formaldehyde Equivalents8 Cyanide9 Formic Acid10 Formyl-CoA and Oxalyl-CoA11 Carbon Monoxide12 Carbon Dioxide13 Conclusions
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12
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Yu Y, van der Donk WA. Biosynthesis of 3-thia-α-amino acids on a carrier peptide. Proc Natl Acad Sci U S A 2022; 119:e2205285119. [PMID: 35787182 PMCID: PMC9303977 DOI: 10.1073/pnas.2205285119] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Accepted: 05/23/2022] [Indexed: 11/18/2022] Open
Abstract
A subset of natural products, such as polyketides and nonribosomal peptides, is biosynthesized while tethered to a carrier peptide via a thioester linkage. Recently, we reported that the biosyntheses of 3-thiaglutamate and ammosamide, single amino acid-derived natural products, employ a very different type of carrier peptide to which the biosynthetic intermediates are bound via an amide linkage. During their biosyntheses, a peptide aminoacyl-transfer ribonucleic acid (tRNA) ligase (PEARL) first loads an amino acid to the C terminus of the carrier peptide for subsequent modification by other enzymes. Proteolytic removal of the modified C-terminal amino acid yields the mature product. We termed natural products that are biosynthesized using such pathways pearlins. To investigate the diversity of pearlins, in this study we experimentally characterized another PEARL-encoding biosynthetic gene cluster (BGC) from Tistrella mobilis (tmo). The enzymes encoded in the tmo BGC transformed cysteine into 3-thiahomoleucine both in vitro and in Escherichia coli. During this process, a cobalamin-dependent radical S-adenosylmethionine (SAM) enzyme catalyzes C-isopropylation. This work illustrates that the biosynthesis of amino acid-derived natural products on a carrier peptide is a widespread strategy in nature and expands the spectrum of thiahemiaminal analogs of amino acids that may serve a broader, currently unknown function.
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Affiliation(s)
- Yue Yu
- Department of Chemistry, University of Illinois at Urbana–Champaign, Urbana, IL 61801
- HHMI, University of Illinois at Urbana–Champaign, Urbana, IL 61801
| | - Wilfred A. van der Donk
- Department of Chemistry, University of Illinois at Urbana–Champaign, Urbana, IL 61801
- HHMI, University of Illinois at Urbana–Champaign, Urbana, IL 61801
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13
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Purification and characterization of sequential cobalamin-dependent radical SAM methylases ThnK and TokK in carbapenem β-lactam antibiotic biosynthesis. Methods Enzymol 2022; 669:29-44. [PMID: 35644176 DOI: 10.1016/bs.mie.2021.09.014] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
ThnK and TokK are cobalamin-dependent radical S-adenosylmethionine enzymes that catalyze sequential methylations of a common carbapenem biosynthetic intermediate. ThnK was an early characterized member of the subfamily of cobalamin-dependent radical S-adenosylmethionine enzymes. Since initial publication of the ThnK function, the field has progressed, and we have made methodological strides in the expression and purification of this enzyme and its ortholog TokK. An optimized protocol for obtaining the enzymes in pure and active form has enabled us to characterize their reactions and gain greater insight into the kinetic behavior of the sequential methylations they catalyze. We share here the methods and strategy that we have developed through our study of these enzymes.
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14
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Soualmia F, Guillot A, Sabat N, Brewee C, Kubiak X, Haumann M, Guinchard X, Benjdia A, Berteau O. Exploring the Biosynthetic Potential of TsrM, a B 12 -dependent Radical SAM Methyltransferase Catalyzing Non-radical Reactions. Chemistry 2022; 28:e202200627. [PMID: 35253932 DOI: 10.1002/chem.202200627] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2022] [Indexed: 12/20/2022]
Abstract
B12 -dependent radical SAM enzymes are an emerging enzyme family with approximately 200,000 proteins. These enzymes have been shown to catalyze chemically challenging reactions such as methyl transfer to sp2- and sp3-hybridized carbon atoms. However, to date we have little information regarding their complex mechanisms and their biosynthetic potential. Here we show, using X-ray absorption spectroscopy, mutagenesis and synthetic probes that the vitamin B12 -dependent radical SAM enzyme TsrM catalyzes not only C- but also N-methyl transfer reactions further expanding its synthetic versatility. We also demonstrate that TsrM has the unique ability to directly transfer a methyl group to the benzyl core of tryptophan, including the least reactive position C4. Collectively, our study supports that TsrM catalyzes non-radical reactions and establishes the usefulness of radical SAM enzymes for novel biosynthetic schemes including serial alkylation reactions at particularly inert C-H bonds.
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Affiliation(s)
- Feryel Soualmia
- Micalis Institute, ChemSyBio, Université Paris-Saclay, INRAE, AgroParisTech, 78350, Jouy-en-Josas, France
| | - Alain Guillot
- Micalis Institute, ChemSyBio, Université Paris-Saclay, INRAE, AgroParisTech, 78350, Jouy-en-Josas, France
| | - Nazarii Sabat
- UPR 2301, Université Paris-Saclay, CNRS, Institut de Chimie des Substances Naturelles, 91198, Gif-sur-Yvette, France
| | - Clémence Brewee
- Micalis Institute, ChemSyBio, Université Paris-Saclay, INRAE, AgroParisTech, 78350, Jouy-en-Josas, France
| | - Xavier Kubiak
- Micalis Institute, ChemSyBio, Université Paris-Saclay, INRAE, AgroParisTech, 78350, Jouy-en-Josas, France
| | - Michael Haumann
- Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195, Berlin, Germany
| | - Xavier Guinchard
- UPR 2301, Université Paris-Saclay, CNRS, Institut de Chimie des Substances Naturelles, 91198, Gif-sur-Yvette, France
| | - Alhosna Benjdia
- Micalis Institute, ChemSyBio, Université Paris-Saclay, INRAE, AgroParisTech, 78350, Jouy-en-Josas, France
| | - Olivier Berteau
- Micalis Institute, ChemSyBio, Université Paris-Saclay, INRAE, AgroParisTech, 78350, Jouy-en-Josas, France
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15
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Gagsteiger J, Jahn S, Heidinger L, Gericke L, Andexer JN, Friedrich T, Loenarz C, Layer G. A Cobalamin‐Dependent Radical SAM Enzyme Catalyzes the Unique Cα‐Methylation of Glutamine in Methyl‐Coenzyme M Reductase. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202204198] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Jana Gagsteiger
- Albert-Ludwigs-Universität Freiburg, Fakultät für Chemie und Pharmazie Institut für Pharmazeutische Wissenschaften, Pharmazeutische Biologie GERMANY
| | - Sören Jahn
- Albert-Ludwigs-Universität Freiburg, Fakultät für Chemie und Pharmazie Institut für Pharmazeutische Wissenschaften, Pharmazeutische und Medizinische Chemie GERMANY
| | - Lorenz Heidinger
- Albert-Ludwigs-Universität Freiburg Institut für Biochemie GERMANY
| | - Lukas Gericke
- Albert-Ludwigs-Universität Freiburg, Fakultät für Chemie und Pharmazie Institut für Pharmazeutische Wissenschaften, Pharmazeutische und Medizinische Chemie GERMANY
| | - Jennifer N. Andexer
- Albert-Ludwigs-Universität Freiburg, Fakultät für Chemie und Pharmazie Institut für Pharmazeutische Wissenschaften, Pharmazeutische und Medizinische Chemie GERMANY
| | - Thorsten Friedrich
- Albert-Ludwigs-Universität Freiburg, Fakultät für Chemie und Pharmazie Institut für Biochemie GERMANY
| | - Christoph Loenarz
- Albert-Ludwigs-Universität Freiburg, Fakultät für Chemie und Pharmazie Institut für Pharmazeutische Wissenschaften, Pharmazeutische und Medizinische Chemie GERMANY
| | - Gunhild Layer
- Albert-Ludwigs-Universität Freiburg, Fakultät für Chemie und Pharmazie Institut für Pharmazeutische Wissenschaften, Pharmazeutische Biologie Stefan-Meier-Str. 19 79104 Freiburg GERMANY
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16
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Wu R, Ding W, Zhang Q. Consecutive Methylation catalyzed by
TsrM
, an atypical Class B radical
SAM
methylase. CHINESE J CHEM 2022. [DOI: 10.1002/cjoc.202200174] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Runze Wu
- Department of Chemistry Fudan University Shanghai 200433 China
| | - Wei Ding
- State Key Laboratory of Microbial Metabolism, School of Life Sciences & Biotechnology, Shanghai Jiao Tong University Shanghai 200240 China
| | - Qi Zhang
- Department of Chemistry Fudan University Shanghai 200433 China
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17
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Ulrich EC, Drennan CL. The Atypical Cobalamin-Dependent S-Adenosyl-l-Methionine Nonradical Methylase TsrM and Its Radical Counterparts. J Am Chem Soc 2022; 144:5673-5684. [PMID: 35344653 PMCID: PMC8992657 DOI: 10.1021/jacs.1c12064] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Cobalamin (Cbl)-dependent S-adenosyl-l-methionine (AdoMet) radical methylases are known for their use of a dual cofactor system to perform challenging radical methylation reactions at unactivated carbon and phosphorus centers. These enzymes are part of a larger subgroup of Cbl-dependent AdoMet radical enzymes that also perform difficult ring contractions and radical rearrangements. This subgroup is a largely untapped reservoir of diverse chemistry that requires steady efforts in biochemical and structural characterization to reveal its complexity. In this Perspective, we highlight the significant efforts over many years to elucidate the function, mechanism, and structure of TsrM, an unexpected nonradical methylase in this subgroup. We also discuss recent achievements in characterizing radical methylase subgroup members that exemplify how key tools in mechanistic enzymology are valuable time and again. Finally, we identify recent enzyme activity studies that have made use of bioinformatic analyses to expand our definition of the subgroup. Additional breakthroughs in radical (and nonradical) enzymatic chemistry and challenging transformations from the unexplored space of this subgroup are undoubtedly on the horizon.
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Affiliation(s)
| | - Catherine L Drennan
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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18
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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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19
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Crystallographic snapshots of a B 12-dependent radical SAM methyltransferase. Nature 2022; 602:336-342. [PMID: 35110733 PMCID: PMC8828468 DOI: 10.1038/s41586-021-04355-9] [Citation(s) in RCA: 25] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Accepted: 12/15/2021] [Indexed: 01/01/2023]
Abstract
By catalysing the microbial formation of methane, methyl-coenzyme M reductase has a central role in the global levels of this greenhouse gas1,2. The activity of methyl-coenzyme M reductase is profoundly affected by several unique post-translational modifications3–6, such as a unique C-methylation reaction catalysed by methanogenesis marker protein 10 (Mmp10), a radical S-adenosyl-l-methionine (SAM) enzyme7,8. Here we report the spectroscopic investigation and atomic resolution structure of Mmp10 from Methanosarcina acetivorans, a unique B12 (cobalamin)-dependent radical SAM enzyme9. The structure of Mmp10 reveals a unique enzyme architecture with four metallic centres and critical structural features involved in the control of catalysis. In addition, the structure of the enzyme–substrate complex offers a glimpse into a B12-dependent radical SAM enzyme in a precatalytic state. By combining electron paramagnetic resonance spectroscopy, structural biology and biochemistry, our study illuminates the mechanism by which the emerging superfamily of B12-dependent radical SAM enzymes catalyse chemically challenging alkylation reactions and identifies distinctive active site rearrangements to provide a structural rationale for the dual use of the SAM cofactor for radical and nucleophilic chemistry. Structural and spectroscopic studies show how a B12-dependent radical SAM enzyme catalyses unique and challenging alkylation chemistry, including protein post-translational modification required for methane biosynthesis.
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20
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Deng WH, Liao RZ. Computational Study revealed a “Pull-Push” Radical Transfer Mechanism of Mmp10-Catalyzed Cδ-methylation of Arginine. Chem Commun (Camb) 2022; 58:7144-7147. [DOI: 10.1039/d2cc02052a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Mmp10 is a B12-dependent SAM radical enzyme that catalyzes Cδ-methylation of arginine. The quantum chemical cluster calculations of Mmp10 revealed a “Pull-Push” radical transfer mechanism in which 5’-deoxyadenosine radical first...
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21
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Liu W, Lavagnino MN, Gould CA, Alcázar J, MacMillan DWC. A biomimetic S H2 cross-coupling mechanism for quaternary sp 3-carbon formation. Science 2021; 374:1258-1263. [PMID: 34762491 DOI: 10.1126/science.abl4322] [Citation(s) in RCA: 56] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
[Figure: see text].
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Affiliation(s)
- Wei Liu
- Merck Center for Catalysis at Princeton University, Princeton, NJ 08544, USA
| | - Marissa N Lavagnino
- Merck Center for Catalysis at Princeton University, Princeton, NJ 08544, USA
| | - Colin A Gould
- Merck Center for Catalysis at Princeton University, Princeton, NJ 08544, USA
| | - Jesús Alcázar
- Discovery Chemistry, Janssen Research and Development, Janssen-Cilag S.A., C/Jarama 75A, Toledo 45007, Spain
| | - David W C MacMillan
- Merck Center for Catalysis at Princeton University, Princeton, NJ 08544, USA
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22
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Wang Z, Kasper A, Mehmood R, Ternei M, Li S, Freundlich JS, Brady SF. Metagenome-Guided Analogue Synthesis Yields Improved Gram-Negative-Active Albicidin- and Cystobactamid-Type Antibiotics. Angew Chem Int Ed Engl 2021; 60:22172-22177. [PMID: 34355488 DOI: 10.1002/anie.202104874] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Revised: 08/05/2021] [Indexed: 11/11/2022]
Abstract
Natural products are a major source of new antibiotics. Here we utilize biosynthetic instructions contained within metagenome-derived congener biosynthetic gene clusters (BGCs) to guide the synthesis of improved antibiotic analogues. Albicidin and cystobactamid are the first members of a new class of broad-spectrum ρ-aminobenzoic acid (PABA)-based antibiotics. Our search for PABA-specific adenylation domain sequences in soil metagenomes revealed that BGCs in this family are common in nature. Twelve BGCs that were bio-informatically predicted to encode six new congeners were recovered from soil metagenomic libraries. Synthesis of these six predicted structures led to the identification of potent antibiotics with changes in their spectrum of activity and the ability to circumvent resistance conferred by endopeptidase cleavage enzymes.
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Affiliation(s)
- Zongqiang Wang
- Laboratory of Genetically Encoded Small Molecules, The Rockefeller University, 1230 York Avenue, New York, NY, 10065, USA
| | - Amanda Kasper
- Laboratory of Genetically Encoded Small Molecules, The Rockefeller University, 1230 York Avenue, New York, NY, 10065, USA
| | - Rabia Mehmood
- Laboratory of Genetically Encoded Small Molecules, The Rockefeller University, 1230 York Avenue, New York, NY, 10065, USA
| | - Melinda Ternei
- Laboratory of Genetically Encoded Small Molecules, The Rockefeller University, 1230 York Avenue, New York, NY, 10065, USA
| | - Shaogang Li
- Department of Medicine, Center for Emerging and Re-emerging Pathogens, Rutgers University-New Jersey Medical School, Newark, NJ, 07103, USA
| | - Joel S Freundlich
- Department of Medicine, Center for Emerging and Re-emerging Pathogens, Rutgers University-New Jersey Medical School, Newark, NJ, 07103, USA
| | - Sean F Brady
- Laboratory of Genetically Encoded Small Molecules, The Rockefeller University, 1230 York Avenue, New York, NY, 10065, USA
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23
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Wang Z, Kasper A, Mehmood R, Ternei M, Li S, Freundlich JS, Brady SF. Metagenome‐Guided Analogue Synthesis Yields Improved Gram‐Negative‐Active Albicidin‐ and Cystobactamid‐Type Antibiotics. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202104874] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- Zongqiang Wang
- Laboratory of Genetically Encoded Small Molecules The Rockefeller University 1230 York Avenue New York NY 10065 USA
| | - Amanda Kasper
- Laboratory of Genetically Encoded Small Molecules The Rockefeller University 1230 York Avenue New York NY 10065 USA
| | - Rabia Mehmood
- Laboratory of Genetically Encoded Small Molecules The Rockefeller University 1230 York Avenue New York NY 10065 USA
| | - Melinda Ternei
- Laboratory of Genetically Encoded Small Molecules The Rockefeller University 1230 York Avenue New York NY 10065 USA
| | - Shaogang Li
- Department of Medicine, Center for Emerging and Re-emerging Pathogens Rutgers University—New Jersey Medical School Newark NJ 07103 USA
| | - Joel S. Freundlich
- Department of Medicine, Center for Emerging and Re-emerging Pathogens Rutgers University—New Jersey Medical School Newark NJ 07103 USA
| | - Sean F. Brady
- Laboratory of Genetically Encoded Small Molecules The Rockefeller University 1230 York Avenue New York NY 10065 USA
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24
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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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25
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