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Cheek LE, Zhu W. Structural features and substrate engagement in peptide-modifying radical SAM enzymes. Arch Biochem Biophys 2024; 756:110012. [PMID: 38663796 DOI: 10.1016/j.abb.2024.110012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2024] [Revised: 04/16/2024] [Accepted: 04/17/2024] [Indexed: 05/04/2024]
Abstract
In recent years, the biological significance of ribosomally synthesized, post-translationally modified peptides (RiPPs) and the intriguing chemistry catalyzed by their tailoring enzymes has garnered significant attention. A subgroup of bacterial radical S-adenosylmethionine (rSAM) enzymes can activate C-H bonds in peptides, which leads to the production of a diverse range of RiPPs. The remarkable ability of these enzymes to facilitate various chemical processes, to generate and harbor high-energy radical species, and to accommodate large substrates with a high degree of flexibility is truly intriguing. The wide substrate scope and diversity of the chemistry performed by rSAM enzymes raise one question: how does the protein environment facilitate these distinct chemical conversions while sharing a similar structural fold? In this review, we discuss recent advances in the field of RiPP-rSAM enzymes, with a particular emphasis on domain architectures and substrate engagements identified by biophysical and structural characterizations. We provide readers with a comparative analysis of six examples of RiPP-rSAM enzymes with experimentally characterized structures. Linking the structural elements and the nature of rSAM-catalyzed RiPP production will provide insight into the functional engineering of enzyme activity to harness their catalytic power in broader applications.
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Affiliation(s)
- Lilly E Cheek
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL, 32306, USA
| | - Wen Zhu
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL, 32306, USA.
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Brimberry M, Corrigan P, Silakov A, Lanzilotta WN. Evidence for Porphyrin-Mediated Electron Transfer in the Radical SAM Enzyme HutW. Biochemistry 2023; 62:1191-1196. [PMID: 36877586 PMCID: PMC10035031 DOI: 10.1021/acs.biochem.2c00474] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/07/2023]
Abstract
Bacteria that infect the human gut must compete for essential nutrients, including iron, under a variety of different metabolic conditions. Several enteric pathogens, including Vibrio cholerae and Escherichia coli O157:H7, have evolved mechanisms to obtain iron from heme in an anaerobic environment. Our laboratory has demonstrated that a radical S-adenosylmethionine (SAM) methyltransferase is responsible for the opening of the heme porphyrin ring and release of iron under anaerobic conditions. Furthermore, the enzyme in V. cholerae, HutW, has recently been shown to accept electrons from NADPH directly when SAM is utilized to initiate the reaction. However, how NADPH, a hydride donor, catalyzes the single electron reduction of a [4Fe-4S] cluster, and/or subsequent electron/proton transfer reactions, was not addressed. In this work, we provide evidence that the substrate, in this case, heme, facilitates electron transfer from NADPH to the [4Fe-4S] cluster. This study uncovers a new electron transfer pathway adopted by radical SAM enzymes and further expands our understanding of these enzymes in bacterial pathogens.
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Affiliation(s)
- Marley Brimberry
- Department of Biochemistry and Molecular Biology & Center for Metalloenzyme Studies, University of Georgia, Athens, Georgia 30602, United States
| | - Patrick Corrigan
- Department of Chemistry, Penn State University, University Park, Pennsylvania 16802, United States
| | - Alexey Silakov
- Department of Chemistry, Penn State University, University Park, Pennsylvania 16802, 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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3
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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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Mathew LG, Brimberry M, Lanzilotta WN. Class C Radical SAM Methyltransferases Involved in Anaerobic Heme Degradation. ACS BIO & MED CHEM AU 2022; 2:120-124. [PMID: 37101744 PMCID: PMC10114669 DOI: 10.1021/acsbiomedchemau.1c00047] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 04/28/2023]
Abstract
Class C radical SAM methyltransferases catalyze a diverse array of difficult chemical transformations in the biosynthesis of a range of compounds of biomedical importance. Phylogenetic analysis suggests that all of these enzymes are related to "CpdH" (formerly "HemN") and "HemW", proteins with essential roles in anaerobic heme biosynthesis and heme transport, respectively. These functions are essential to anaerobic metabolism in Escherichia coli. Interestingly, evolution has come full circle, and the divergence of this protein sequence/fold has resulted in the class C radical SAM methyltransferases. Several pathogenic organisms have further adapted this fold to catalyze the anaerobic degradation of heme. In this review, we summarize what is known about the mechanism of anaerobic heme degradation and the evolutionary implications.
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Affiliation(s)
- Jinduo Cheng
- 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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Cheng J, Liu WQ, Zhu X, Zhang Q. Functional Diversity of HemN-like Proteins. ACS BIO & MED CHEM AU 2022; 2:109-119. [PMID: 37101745 PMCID: PMC10114718 DOI: 10.1021/acsbiomedchemau.1c00058] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
HemN is a radical S-adenosylmethionine (SAM) enzyme that catalyzes the anaerobic oxidative decarboxylation of coproporphyrinogen III to produce protoporphyrinogen IX, a key intermediate in heme biosynthesis. Proteins homologous to HemN (HemN-like proteins) are widespread in both prokaryotes and eukaryotes. Although these proteins are in most cases annotated as anaerobic coproporphyrinogen III oxidases (CPOs) in the public database, many of them are actually not CPOs but have diverse functions such as methyltransferases, cyclopropanases, heme chaperones, to name a few. This Perspective discusses the recent advances in the understanding of HemN-like proteins, and particular focus is placed on the diverse chemistries and functions of this growing protein family.
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Affiliation(s)
- Jinduo Cheng
- Department of Chemistry, Fudan University, Shanghai, 200433, China
| | - Wan-Qiu Liu
- Department of Chemistry, Fudan University, Shanghai, 200433, China
| | - Xiaoyu Zhu
- Department of Chemistry, Fudan University, Shanghai, 200433, China
| | - Qi Zhang
- Department of Chemistry, Fudan University, Shanghai, 200433, China
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Ma S, Mandalapu D, Wang S, Zhang Q. Biosynthesis of cyclopropane in natural products. Nat Prod Rep 2021; 39:926-945. [PMID: 34860231 DOI: 10.1039/d1np00065a] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Covering: 2012 to 2021Cyclopropane attracts wide interests in the fields of synthetic and pharmaceutical chemistry, and chemical biology because of its unique structural and chemical properties. This structural motif is widespread in natural products, and is usually essential for biological activities. Nature has evolved diverse strategies to access this structural motif, and increasing knowledge of the enzymes forming cyclopropane (i.e., cyclopropanases) has been revealed over the last two decades. Here, the scientific literature from the last two decades relating to cyclopropane biosynthesis is summarized, and the enzymatic cyclopropanations, according to reaction mechanism, which can be grouped into two major pathways according to whether the reaction involves an exogenous C1 unit from S-adenosylmethionine (SAM) or not, is discussed. The reactions can further be classified based on the key intermediates required prior to cyclopropane formation, which can be carbocations, carbanions, or carbon radicals. Besides the general biosynthetic pathways of the cyclopropane-containing natural products, particular emphasis is placed on the mechanism and engineering of the enzymes required for forming this unique structure motif.
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Affiliation(s)
- Suze Ma
- Department of Chemistry, Fudan University, Shanghai, 200433, China.
| | | | - Shu Wang
- Department of Chemistry, Fudan University, Shanghai, 200433, China.
| | - Qi Zhang
- Department of Chemistry, Fudan University, Shanghai, 200433, China.
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