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Sinner EK, Li R, Marous DR, Townsend CA. ThnL, a B12-dependent radical S-adenosylmethionine enzyme, catalyzes thioether bond formation in carbapenem biosynthesis. Proc Natl Acad Sci U S A 2022; 119:e2206494119. [PMID: 35969793 PMCID: PMC9407657 DOI: 10.1073/pnas.2206494119] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Accepted: 07/19/2022] [Indexed: 11/18/2022] Open
Abstract
Complex carbapenems are important clinical antibiotics used to treat recalcitrant infections. Their biosynthetic gene clusters contain three essential B12-dependent radical S-adenosylmethionine (rSAM) enzymes. The majority of characterized enzymes in this subfamily catalyze methyl transfer, but only one is required to sequentially install all methionine-derived carbons in complex carbapenems. Therefore, it is probable that the other two rSAM enzymes have noncanonical functions. Through a series of fermentation and in vitro experiments, we show that ThnL uses radical SAM chemistry to catalyze thioether bond formation between C2 of a carbapenam precursor and pantetheine, uniting initial bicycle assembly common to all carbapenems with later tailoring events unique to complex carbapenems. ThnL also catalyzes reversible thiol/disulfide redox on pantetheine. Neither of these functions has been observed previously in a B12-dependent radical SAM enzyme. ThnL expands the known activity of this subclass of enzymes beyond carbon-carbon bond formation or rearrangement. It is also the only radical SAM enzyme currently known to catalyze carbon-sulfur bond formation with only an rSAM Fe-S cluster and no additional auxiliary clusters.
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Affiliation(s)
- Erica K. Sinner
- Department of Chemistry, Johns Hopkins University, Baltimore, MD 21218
| | - Rongfeng Li
- Department of Chemistry, Johns Hopkins University, Baltimore, MD 21218
| | - Daniel R. Marous
- Department of Chemistry, Johns Hopkins University, Baltimore, MD 21218
| | - Craig A. Townsend
- Department of Chemistry, Johns Hopkins University, Baltimore, MD 21218
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2
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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: 4.0] [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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3
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Sinner EK, Lichstrahl MS, Li R, Marous DR, Townsend CA. Methylations in complex carbapenem biosynthesis are catalyzed by a single cobalamin-dependent radical S-adenosylmethionine enzyme. Chem Commun (Camb) 2019; 55:14934-14937. [PMID: 31774078 DOI: 10.1039/c9cc07197k] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Complex carbapenem β-lactam antibiotics contain diverse C6 alkyl substituents constructed by cobalamin-dependent radical SAM enzymes. TokK installs the C6 isopropyl chain found in asparenomycin. Time-course analyses of TokK and its ortholog ThnK, which forms the C6 ethyl chain of thienamycin, indicate that catalysis occurs through a sequence of discrete, non-processive methyl transfers.
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Affiliation(s)
- Erica K Sinner
- Department of Chemistry, Johns Hopkins University, 3400 N Charles St., Baltimore, MD 21218, USA.
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4
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Kaysser L. Built to bind: biosynthetic strategies for the formation of small-molecule protease inhibitors. Nat Prod Rep 2019; 36:1654-1686. [DOI: 10.1039/c8np00095f] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The discovery and characterization of natural product protease inhibitors has inspired the development of numerous pharmaceutical agents.
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Affiliation(s)
- Leonard Kaysser
- Department of Pharmaceutical Biology
- University of Tübingen
- 72076 Tübingen
- Germany
- German Centre for Infection Research (DZIF)
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5
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Rabe P, Kamps JJAG, Schofield CJ, Lohans CT. Roles of 2-oxoglutarate oxygenases and isopenicillin N synthase in β-lactam biosynthesis. Nat Prod Rep 2018; 35:735-756. [PMID: 29808887 PMCID: PMC6097109 DOI: 10.1039/c8np00002f] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Indexed: 01/01/2023]
Abstract
Covering: up to 2017 2-Oxoglutarate (2OG) dependent oxygenases and the homologous oxidase isopenicillin N synthase (IPNS) play crucial roles in the biosynthesis of β-lactam ring containing natural products. IPNS catalyses formation of the bicyclic penicillin nucleus from a tripeptide. 2OG oxygenases catalyse reactions that diversify the chemistry of β-lactams formed by both IPNS and non-oxidative enzymes. Reactions catalysed by the 2OG oxygenases of β-lactam biosynthesis not only involve their typical hydroxylation reactions, but also desaturation, epimerisation, rearrangement, and ring-forming reactions. Some of the enzymes involved in β-lactam biosynthesis exhibit remarkable substrate and product selectivities. We review the roles of 2OG oxygenases and IPNS in β-lactam biosynthesis, highlighting opportunities for application of knowledge of their roles, structures, and mechanisms.
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Affiliation(s)
- Patrick Rabe
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, UK.
| | - Jos J A G Kamps
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, UK.
| | - Christopher J Schofield
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, UK.
| | - Christopher T Lohans
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, UK.
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6
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Synthesis of cis- and trans-(±)-3-mercaptoproline and pipecolic acid derivatives via thio-Michael addition. Tetrahedron Lett 2018. [DOI: 10.1016/j.tetlet.2018.03.057] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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7
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Janata J, Kamenik Z, Gazak R, Kadlcik S, Najmanova L. Biosynthesis and incorporation of an alkylproline-derivative (APD) precursor into complex natural products. Nat Prod Rep 2018. [DOI: 10.1039/c7np00047b] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
This review covers the biosynthetic and evolutionary aspects of lincosamide antibiotics, antitumour pyrrolobenzodiazepines (PBDs) and the quorum-sensing molecule hormaomycin.
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Affiliation(s)
- J. Janata
- Institute of Microbiology
- Czech Academy of Sciences
- BIOCEV
- Vestec
- Czech Republic
| | - Z. Kamenik
- Institute of Microbiology
- Czech Academy of Sciences
- BIOCEV
- Vestec
- Czech Republic
| | - R. Gazak
- Institute of Microbiology
- Czech Academy of Sciences
- BIOCEV
- Vestec
- Czech Republic
| | - S. Kadlcik
- Institute of Microbiology
- Czech Academy of Sciences
- BIOCEV
- Vestec
- Czech Republic
| | - L. Najmanova
- Institute of Microbiology
- Czech Academy of Sciences
- BIOCEV
- Vestec
- Czech Republic
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8
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Dunbar KL, Scharf DH, Litomska A, Hertweck C. Enzymatic Carbon-Sulfur Bond Formation in Natural Product Biosynthesis. Chem Rev 2017; 117:5521-5577. [PMID: 28418240 DOI: 10.1021/acs.chemrev.6b00697] [Citation(s) in RCA: 391] [Impact Index Per Article: 48.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Sulfur plays a critical role for the development and maintenance of life on earth, which is reflected by the wealth of primary metabolites, macromolecules, and cofactors bearing this element. Whereas a large body of knowledge has existed for sulfur trafficking in primary metabolism, the secondary metabolism involving sulfur has long been neglected. Yet, diverse sulfur functionalities have a major impact on the biological activities of natural products. Recent research at the genetic, biochemical, and chemical levels has unearthed a broad range of enzymes, sulfur shuttles, and chemical mechanisms for generating carbon-sulfur bonds. This Review will give the first systematic overview on enzymes catalyzing the formation of organosulfur natural products.
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Affiliation(s)
- Kyle L Dunbar
- Department of Biomolecular Chemistry, Leibniz Institute for Natural Product Research and Infection Biology (HKI) , Beutenbergstrasse 11a, 07745 Jena, Germany
| | - Daniel H Scharf
- Life Sciences Institute, University of Michigan , 210 Washtenaw Avenue, Ann Arbor, Michigan 48109-2216, United States
| | - Agnieszka Litomska
- Department of Biomolecular Chemistry, Leibniz Institute for Natural Product Research and Infection Biology (HKI) , Beutenbergstrasse 11a, 07745 Jena, Germany
| | - Christian Hertweck
- Department of Biomolecular Chemistry, Leibniz Institute for Natural Product Research and Infection Biology (HKI) , Beutenbergstrasse 11a, 07745 Jena, Germany.,Friedrich Schiller University , 07743 Jena, Germany
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9
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Trautman EP, Crawford JM. Linking Biosynthetic Gene Clusters to their Metabolites via Pathway- Targeted Molecular Networking. Curr Top Med Chem 2016; 16:1705-16. [PMID: 26456470 PMCID: PMC5055756 DOI: 10.2174/1568026616666151012111046] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2015] [Revised: 08/25/2015] [Accepted: 09/08/2015] [Indexed: 12/16/2022]
Abstract
The connection of microbial biosynthetic gene clusters to the small molecule metabolites they encode is central to the discovery and characterization of new metabolic pathways with ecological and pharmacological potential. With increasing microbial genome sequence information being deposited into publicly available databases, it is clear that microbes have the coding capacity for many more biologically active small molecules than previously realized. Of increasing interest are the small molecules encoded by the human microbiome, as these metabolites likely mediate a variety of currently uncharacterized human-microbe interactions that influence health and disease. In this mini-review, we describe the ongoing biosynthetic, structural, and functional characterizations of the genotoxic colibactin pathway in gut bacteria as a thematic example of linking biosynthetic gene clusters to their metabolites. We also highlight other natural products that are produced through analogous biosynthetic logic and comment on some current disconnects between bioinformatics predictions and experimental structural characterizations. Lastly, we describe the use of pathway-targeted molecular networking as a tool to characterize secondary metabolic pathways within complex metabolomes and to aid in downstream metabolite structural elucidation efforts.
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Affiliation(s)
| | - Jason M Crawford
- Department of Chemistry, Faculty of Yale University, P.O. Box: 27392, West Haven, CT, 06516, USA.
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10
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Townsend CA. Convergent biosynthetic pathways to β-lactam antibiotics. Curr Opin Chem Biol 2016; 35:97-108. [PMID: 27693891 DOI: 10.1016/j.cbpa.2016.09.013] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Revised: 09/14/2016] [Accepted: 09/15/2016] [Indexed: 02/05/2023]
Abstract
Five naturally-occurring families of β-lactams have inspired a class of drugs that constitute >60% of the antimicrobials used in human medicine. Their biosynthetic pathways reveal highly individualized synthetic strategies that yet converge on a common azetidinone ring assembled in structural contexts that confer selective binding and inhibition of d,d-transpeptidases that play essential roles in bacterial cell wall (peptidoglycan) biosynthesis. These enzymes belong to a single 'clan' of evolutionarily distinct serine hydrolases whose active site geometry and mechanism of action is specifically matched by these antibiotics for inactivation that is kinetically competitive with their native function. Unusual enzyme-mediated reactions and catalytic multitasking in these pathways are discussed with particular attention to the diverse ways the β-lactam itself is generated, and more broadly how the intrinsic reactivity of this core structural element is modulated in natural systems through the introduction of ring strain and electronic effects.
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Affiliation(s)
- Craig A Townsend
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA.
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11
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Abstract
Low-molecular-weight (LMW) thiols are extensively involved in the maintenance of cellular redox potentials and the protection of cells from a variety of reactive chemical and electrophilic species. However, we recently found that the metabolic coupling of two LMW thiols - mycothiol (MSH) and ergothioneine (EGT) - programs the biosynthesis of the anti-infective agent lincomycin A. Remarkably, such a constructive role of the thiols in the biosynthesis of natural products has so far received relatively little attention. We speculate that the unusual thiol EGT might function as a chiral thiolation carrier (for modification) and a novel activator (for glycosylation) of sugar. Additionally, we examine recent evidence for LMW thiols (MSH and others) as sulfur donors of sulfur-containing natural products. Clearly, the LMW thiols have more diverse activities beyond cell protection, and more attention should be paid to the correlation of their functions with thiol-dependent enzymes.
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Affiliation(s)
- Min Wang
- State Key Laboratory of Bioorganic and Natural Products Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai, China
| | - Qunfei Zhao
- State Key Laboratory of Bioorganic and Natural Products Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai, China
| | - Wen Liu
- State Key Laboratory of Bioorganic and Natural Products Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai, China.,Huzhou Center of Bio-Synthetic Innovation, Huzhou, China
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12
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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: 70] [Impact Index Per Article: 7.0] [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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13
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Gaudelli NM, Long DH, Townsend CA. β-Lactam formation by a non-ribosomal peptide synthetase during antibiotic biosynthesis. Nature 2015; 520:383-7. [PMID: 25624104 PMCID: PMC4401618 DOI: 10.1038/nature14100] [Citation(s) in RCA: 96] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2014] [Accepted: 11/19/2014] [Indexed: 01/23/2023]
Abstract
Non-ribosomal peptide synthetases (NRPSs) are giant enzymes comprised of modules that house repeated sets of functional domains, which select, activate and couple amino acids drawn from a pool of nearly 500 potential building blocks.1 The structurally and stereochemically diverse peptides generated in this manner underlie the biosynthesis of a large sector of natural products. Many of their derived metabolites are bioactive such as the antibiotics vancomycin, bacitracin, daptomycin and the β-lactam-containing penicillins, cephalosporins and nocardicins. Although penicillins and cephalosporins are synthesised from a classically derived NRPS tripeptide (from ACVS, δ-(L-α-aminoadipyl)–L-cysteinyl–D-valine synthetase)2, we now report an unprecedented NRPS activity to both assemble a serine-containing peptide and mediate its cyclisation to the critical β-lactam ring of the nocardicin family of antibiotics. A histidine-rich condensation (C) domain, which typically carries out peptide bond formation during product assembly, was found to also synthesise the embedded 4-membered ring. Here, a mechanism is proposed and supporting experiments are described, which is distinct from the pathways that have evolved to the three other β-lactam antibiotic families: penicillin/cephalosporins, clavams and carbapenems. These findings raise the possibility that β-lactam rings can be regio- and stereospecifically integrated into engineered peptides for application as, for example, targeted protease inactivators.3,4
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Affiliation(s)
- Nicole M Gaudelli
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - Darcie H Long
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - Craig A Townsend
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, USA
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14
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Buller AR, Freeman MF, Schildbach JF, Townsend CA. Exploring the role of conformational heterogeneity in cis-autoproteolytic activation of ThnT. Biochemistry 2014; 53:4273-81. [PMID: 24933323 PMCID: PMC4095933 DOI: 10.1021/bi500385d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
In
the past decade, there have been major achievements in understanding
the relationship between enzyme catalysis and protein structural plasticity.
In autoprocessing systems, however, there is a sparsity of direct
evidence of the role of conformational dynamics, which are complicated
by their intrinsic chemical reactivity. ThnT is an autoproteolytically
activated enzyme involved in the biosynthesis of the β-lactam
antibiotic thienamycin. Conservative mutation of ThnT results in multiple
conformational states that can be observed via X-ray crystallography,
establishing ThnT as a representative and revealing system for studing
how conformational dynamics control autoactivation at a molecular
level. Removal of the nucleophile by mutation to Ala disrupts the
population of a reactive state and causes widespread structural changes
from a conformation that promotes autoproteolysis to one associated
with substrate catalysis. Finer probing of the active site polysterism
was achieved by EtHg derivatization of the nucleophile, which indicates
the active site and a neighboring loop have coupled dynamics. Disruption
of these interactions by mutagenesis precludes the ability to observe
a reactive state through X-ray crystallography, and application of
this insight to other autoproteolytically activated enzymes offers
an explanation for the widespread crystallization of inactive states.
We suggest that the N → O(S) acyl shift in cis-autoproteolysis might occur through a si-face attack,
thereby unifying the fundamental chemistry of these enzymes through
a common mechanism.
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Affiliation(s)
- Andrew R Buller
- Department of Biophysics, Johns Hopkins University , Baltimore, Maryland 21218, United States
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15
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Braña AF, Rodríguez M, Pahari P, Rohr J, García LA, Blanco G. Activation and silencing of secondary metabolites in Streptomyces albus and Streptomyces lividans after transformation with cosmids containing the thienamycin gene cluster from Streptomyces cattleya. Arch Microbiol 2014; 196:345-55. [PMID: 24633227 DOI: 10.1007/s00203-014-0977-z] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2013] [Revised: 02/17/2014] [Accepted: 03/04/2014] [Indexed: 01/09/2023]
Abstract
Activation and silencing of antibiotic production was achieved in Streptomyces albus J1074 and Streptomyces lividans TK21 after introduction of genes within the thienamycin cluster from S. cattleya. Dramatic phenotypic and metabolic changes, involving activation of multiple silent secondary metabolites and silencing of others normally produced, were found in recombinant strains harbouring the thienamycin cluster in comparison to the parental strains. In S. albus, ultra-performance liquid chromatography purification and NMR structural elucidation revealed the identity of four structurally related activated compounds: the antibiotics paulomycins A, B and the paulomenols A and B. Four volatile compounds whose biosynthesis was switched off were identified by gas chromatography-mass spectrometry analyses and databases comparison as pyrazines; including tetramethylpyrazine, a compound with important clinical applications to our knowledge never reported to be produced by Streptomyces. In addition, this work revealed the potential of S. albus to produce many others secondary metabolites normally obtained from plants, including compounds of medical relevance as dihydro-β-agarofuran and of interest in perfume industry as β-patchoulene, suggesting that it might be an alternative model for their industrial production. In S. lividans, actinorhodins production was strongly activated in the recombinant strains whereas undecylprodigiosins were significantly reduced. Activation of cryptic metabolites in Streptomyces species might represent an alternative approach for pharmaceutical drug discovery.
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Affiliation(s)
- Alfredo F Braña
- Departamento de Biología Funcional e Instituto Universitario de Oncología del Principado de Asturias, Universidad de Oviedo, 33006, Oviedo, Spain
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16
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Li R, Lloyd EP, Moshos KA, Townsend CA. Identification and characterization of the carbapenem MM 4550 and its gene cluster in Streptomyces argenteolus ATCC 11009. Chembiochem 2014; 15:320-31. [PMID: 24420617 PMCID: PMC3972073 DOI: 10.1002/cbic.201300319] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2013] [Revised: 10/25/2013] [Indexed: 11/11/2022]
Abstract
Nearly 50 naturally occurring carbapenem β-lactam antibiotics, most produced by Streptomyces, have been identified. The structural diversity of these compounds is limited to variance of the C-2 and C-6 side chains as well as the stereochemistry at C-5/C-6. These structural motifs are of interest both for their antibiotic effects and their biosynthesis. Although the thienamycin gene cluster is the only active gene cluster publically available in this group, more comparative information is needed to understand the genetic basis of these structural differences. We report here the identification of MM 4550, a member of the olivanic acids, as the major carbapenem produced by Streptomyces argenteolus ATCC 11009. Its gene cluster was also identified by degenerate PCR and targeted gene inactivation. Sequence analysis revealed that the genes encoding the biosynthesis of the bicyclic core and the C-6 and C-2 side chains are well conserved in the MM 4550 and thienamycin gene clusters. Three new genes, cmmSu, cmm17 and cmmPah were found in the new cluster, and their putative functions in the sulfonation and epimerization of MM 4550 are proposed. Gene inactivation showed that, in addition to cmmI, two new genes, cmm22 and -23, encode a two-component response system thought to regulate the production of MM 4550. Overexpression of cmmI, cmm22 and cmm23 promoted MM 4550 production in an engineered strain. Finally, the involvement and putative roles of all genes in the MM 4550 cluster are proposed based on the results of bioinformatics analysis, gene inactivation, and analysis of disruption mutants. Overall, the differences between the thienamycin and MM 4550 gene clusters are reflected in characteristic structural elements and provide new insights into the biosynthesis of the complex carbapenems.
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Affiliation(s)
- Rongfeng Li
- Department of Chemistry, The Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218 (USA)
| | - Evan P. Lloyd
- Department of Chemistry, The Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218 (USA)
| | | | - Craig. A Townsend
- Department of Chemistry, The Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218 (USA)
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17
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Scharf DH, Chankhamjon P, Scherlach K, Heinekamp T, Willing K, Brakhage AA, Hertweck C. Epidithiodiketopiperazine biosynthesis: a four-enzyme cascade converts glutathione conjugates into transannular disulfide bridges. Angew Chem Int Ed Engl 2013; 52:11092-5. [PMID: 24039048 DOI: 10.1002/anie.201305059] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2013] [Indexed: 01/13/2023]
Abstract
Enzyme quartet: Isolation of the first sulfur-bearing intermediate of the gliotoxin pathway in Aspergillus fumigatus and successful in vitro conversion of the bisglutathione adduct into an intact epidithiodiketopiperazine by a four-enzyme cascade (including glutamyltransferase GliK and dipeptidase GliJ) revealed an outstanding adaptation of a primary metabolic pathway into natural product biosynthesis that is widespread in fungi.
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Affiliation(s)
- Daniel H Scharf
- Depts. of Molecular and Applied Microbiology, Biomolecular Chemistry, and Bio Pilot Plant, Leibniz Institute for Natural Product Research and Infection Biology, HKI, Beutenbergstrasse 11a, 07745 Jena (Germany)
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18
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Scharf DH, Chankhamjon P, Scherlach K, Heinekamp T, Willing K, Brakhage AA, Hertweck C. Epidithiodiketopiperazine Biosynthesis: A Four-Enzyme Cascade Converts Glutathione Conjugates into Transannular Disulfide Bridges. Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201305059] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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19
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Gaudelli NM, Townsend CA. Stereocontrolled syntheses of peptide thioesters containing modified seryl residues as probes of antibiotic biosynthesis. J Org Chem 2013; 78:6412-26. [PMID: 23758494 PMCID: PMC3898789 DOI: 10.1021/jo4007893] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Methods have been developed to synthesize tri- and pentapeptide thioesters containing one or more p-(hydroxyphenyl)glycine (pHPG) residues and L-serine, some where the latter is O-phosphorylated, O-acetylated, or exists as a β-lactam. Selection of orthogonal protection strategies and development of conditions to achieve seryl O-phosphorylation without β-elimination and to maintain stereochemical control, especially simultaneously at exceptionally base-labile pHPG α-carbons, are described. Intramolecular closure of a seryl peptide to a β-lactam-containing peptide and the syntheses of corresponding thioester analogues are also reported. Modification of classical Mitsunobu conditions is described in the synthesis of the β-lactam-containing products, and in a broadly useful observation, it was found that simple exclusion of light from the P(OEt)3-mediated Mitsunobu ring closure afforded yields of >95%, presumably owing to reduced photodegradation of the azodicarboxylate used. These sensitive potential substrates and products will be used in mechanistic studies of the two nonribosomal peptide synthetases NocA and NocB that lie at the heart of nocardicin biosynthesis, a family of monocyclic β-lactam antibiotics.
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Affiliation(s)
| | - Craig A. Townsend
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218
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20
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Hamed RB, Gomez-Castellanos JR, Henry L, Ducho C, McDonough MA, Schofield CJ. The enzymes of β-lactam biosynthesis. Nat Prod Rep 2013; 30:21-107. [DOI: 10.1039/c2np20065a] [Citation(s) in RCA: 146] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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21
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Buller AR, Labonte JW, Freeman MF, Wright NT, Schildbach JF, Townsend CA. Autoproteolytic activation of ThnT results in structural reorganization necessary for substrate binding and catalysis. J Mol Biol 2012; 422:508-18. [PMID: 22706025 PMCID: PMC3428426 DOI: 10.1016/j.jmb.2012.06.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2012] [Revised: 06/02/2012] [Accepted: 06/08/2012] [Indexed: 11/01/2022]
Abstract
cis-Autoproteolysis is a post-translational modification necessary for the function of ThnT, an enzyme involved in the biosynthesis of the β-lactam antibiotic thienamycin. This modification generates an N-terminal threonine nucleophile that is used to hydrolyze the pantetheinyl moiety of its natural substrate. We determined the crystal structure of autoactivated ThnT to 1.8Å through X-ray crystallography. Comparison to a mutationally inactivated precursor structure revealed several large conformational rearrangements near the active site. To probe the relevance of these transitions, we designed a pantetheine-like chloromethyl ketone inactivator and co-crystallized it with ThnT. Although this class of inhibitor has been in use for several decades, the mode of inactivation had not been determined for an enzyme that uses an N-terminal nucleophile. The co-crystal structure revealed the chloromethyl ketone bound to the N-terminal nucleophile of ThnT through an ether linkage, and analysis suggests inactivation through a direct displacement mechanism. More importantly, this inactivated complex shows that three regions of ThnT that are critical to the formation of the substrate binding pocket undergo rearrangement upon autoproteolysis. Comparison of ThnT with other autoproteolytic enzymes of disparate evolutionary lineage revealed a high degree of similarity within the proenzyme active site, reflecting shared chemical constraints. However, after autoproteolysis, many enzymes, like ThnT, are observed to rearrange in order to accommodate their specific substrate. We propose that this is a general phenomenon, whereby autoprocessing systems with shared chemistry may possess similar structural features that dissipate upon rearrangement into a mature state.
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Affiliation(s)
- Andrew R. Buller
- Department of Biophysics, The Johns Hopkins University, Baltimore, MD 21218, USA
| | - Jason W. Labonte
- Department of Chemistry, The Johns Hopkins University, Baltimore, MD 21218, USA
| | - Michael F. Freeman
- Department of Chemistry, The Johns Hopkins University, Baltimore, MD 21218, USA
| | - Nathan T. Wright
- Department of Biology, The Johns Hopkins University, Baltimore, MD 21218, USA
| | - Joel F. Schildbach
- Department of Biology, The Johns Hopkins University, Baltimore, MD 21218, USA
| | - Craig A. Townsend
- Department of Biophysics, The Johns Hopkins University, Baltimore, MD 21218, USA
- Department of Chemistry, The Johns Hopkins University, Baltimore, MD 21218, USA
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22
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Insights into cis-autoproteolysis reveal a reactive state formed through conformational rearrangement. Proc Natl Acad Sci U S A 2012; 109:2308-13. [PMID: 22308359 DOI: 10.1073/pnas.1113633109] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
ThnT is a pantetheine hydrolase from the DmpA/OAT superfamily involved in the biosynthesis of the β-lactam antibiotic thienamycin. We performed a structural and mechanistic investigation into the cis-autoproteolytic activation of ThnT, a process that has not previously been subject to analysis within this superfamily of enzymes. Removal of the γ-methyl of the threonine nucleophile resulted in a rate deceleration that we attribute to a reduction in the population of the reactive rotamer. This phenomenon is broadly applicable and constitutes a rationale for the evolutionary selection of threonine nucleophiles in autoproteolytic systems. Conservative substitution of the nucleophile (T282C) allowed determination of a 1.6-Å proenzyme ThnT crystal structure, which revealed a level of structural flexibility not previously observed within an autoprocessing active site. We assigned the major conformer as a nonreactive state that is unable to populate a reactive rotamer. Our analysis shows the system is activated by a structural rearrangement that places the scissile amide into an oxyanion hole and forces the nucleophilic residue into a forbidden region of Ramachandran space. We propose that conformational strain may drive autoprocessing through the destabilization of nonproductive states. Comparison of our data with previous reports uncovered evidence that many inactivated structures display nonreactive conformations. For penicillin and cephalosporin acylases, this discrepancy between structure and function may be resolved by invoking the presence of a hidden conformational state, similar to that reported here for ThnT.
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23
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Comparative analysis of a cryptic thienamycin-like gene cluster identified in Streptomyces flavogriseus by genome mining. Arch Microbiol 2011; 194:549-55. [DOI: 10.1007/s00203-011-0781-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2011] [Revised: 11/28/2011] [Accepted: 12/09/2011] [Indexed: 10/14/2022]
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24
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Bodner MJ, Li R, Phelan RM, Freeman MF, Moshos KA, Lloyd EP, Townsend CA. Definition of the common and divergent steps in carbapenem β-lactam antibiotic biosynthesis. Chembiochem 2011; 12:2159-65. [PMID: 21913298 PMCID: PMC3281309 DOI: 10.1002/cbic.201100366] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2011] [Indexed: 11/11/2022]
Abstract
Approximately 50 naturally occurring carbapenem β-lactam antibiotics are known. All but one of these have been isolated from Streptomyces species and are disubstituted structural variants of a simple core that is synthesized by Pectobacterium carotovorum (Erwinia carotovora), a phylogenetically distant plant pathogen. While the biosynthesis of the simple carbapenem, (5R)-carbapen-2-em-3-carboxylic acid, is impressively efficient requiring only three enzymes, CarA, CarB and CarC, the formation of thienamycin, one of the former group of metabolites from Streptomyces, is markedly more complex. Despite their phylogenetic separation, bioinformatic analysis of the encoding gene clusters suggests that the two pathways could be related. Here we demonstrate with gene swapping, stereochemical and kinetics experiments that CarB and CarA and their S. cattleya orthologues, ThnE and ThnM, respectively, are functionally and stereochemically equivalent, although their catalytic efficiencies differ. The biosynthetic pathways, therefore, to thienamycin, and likely to the other disubstituted carbapenems, and to the simplest carbapenem, (5R)-carbapen-2-em-3-carboxylic acid, are initiated in the same manner, but share only two common steps before diverging.
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Affiliation(s)
- Micah J. Bodner
- Department of Chemistry, The Johns Hopkins University Baltimore, Maryland 21218 (USA)
| | - Rongfeng Li
- Department of Chemistry, The Johns Hopkins University Baltimore, Maryland 21218 (USA)
| | - Ryan M. Phelan
- Department of Chemistry, The Johns Hopkins University Baltimore, Maryland 21218 (USA)
| | - Michael F. Freeman
- Department of Chemistry, The Johns Hopkins University Baltimore, Maryland 21218 (USA)
| | - Kristos A. Moshos
- Department of Chemistry, The Johns Hopkins University Baltimore, Maryland 21218 (USA)
| | - Evan P. Lloyd
- Department of Chemistry, The Johns Hopkins University Baltimore, Maryland 21218 (USA)
| | - Craig A. Townsend
- Department of Chemistry, The Johns Hopkins University Baltimore, Maryland 21218 (USA)
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25
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Ultraviolet derivatization of low-molecular-mass thiols for high performance liquid chromatography and capillary electrophoresis analysis. J Chromatogr B Analyt Technol Biomed Life Sci 2011; 879:1290-307. [DOI: 10.1016/j.jchromb.2010.10.035] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2010] [Revised: 10/20/2010] [Accepted: 10/28/2010] [Indexed: 11/30/2022]
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26
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Rodríguez M, Núñez LE, Braña AF, Méndez C, Salas JA, Blanco G. Mutational analysis of the thienamycin biosynthetic gene cluster from Streptomyces cattleya. Antimicrob Agents Chemother 2011; 55:1638-49. [PMID: 21263049 PMCID: PMC3067130 DOI: 10.1128/aac.01366-10] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2010] [Revised: 12/09/2010] [Accepted: 01/14/2011] [Indexed: 11/20/2022] Open
Abstract
The generation of non-thienamycin-producing mutants with mutations in the thnL, thnN, thnO, and thnI genes within the thn gene cluster from Streptomyces cattleya and their involvement in thienamycin biosynthesis and regulation were previously reported. Four additional mutations were independently generated in the thnP, thnG, thnR, and thnT genes by insertional inactivation. Only the first two genes were found to play a role in thienamycin biosynthesis, since these mutations negatively or positively affect antibiotic production. A mutation of thnP results in the absence of thienamycin production, whereas a 2- to 3-fold increase in thienamycin production was observed for the thnG mutant. On the other hand, mutations in thnR and thnT showed that although these genes were previously reported to participate in this pathway, they seem to be nonessential for thienamycin biosynthesis, as thienamycin production was not affected in these mutants. High-performance liquid chromatography (HPLC)-mass spectrometry (MS) analysis of all available mutants revealed some putative intermediates in the thienamycin biosynthetic pathway. A compound with a mass corresponding to carbapenam-3-carboxylic acid was detected in some of the mutants, suggesting that the assembly of the bicyclic nucleus of thienamycin might proceed in a way analogous to that of the simplest natural carbapenem, 1-carbapen-2-em-3-carboxylic acid biosynthesis. The accumulation of a compound with a mass corresponding to 2,3-dihydrothienamycin in the thnG mutant suggests that it might be the last intermediate in the biosynthetic pathway. These data, together with the establishment of cross-feeding relationships by the cosynthesis analysis of the non-thienamycin-producing mutants, lead to a proposal for some enzymatic steps during thienamycin assembly.
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Affiliation(s)
- Miriam Rodríguez
- Departamento de Biología Funcional e Instituto Universitario de Oncología del Principado de Asturias, Universidad de Oviedo, 33006 Oviedo, Spain
| | - Luz Elena Núñez
- Departamento de Biología Funcional e Instituto Universitario de Oncología del Principado de Asturias, Universidad de Oviedo, 33006 Oviedo, Spain
| | - Alfredo F. Braña
- Departamento de Biología Funcional e Instituto Universitario de Oncología del Principado de Asturias, Universidad de Oviedo, 33006 Oviedo, Spain
| | - Carmen Méndez
- Departamento de Biología Funcional e Instituto Universitario de Oncología del Principado de Asturias, Universidad de Oviedo, 33006 Oviedo, Spain
| | - José A. Salas
- Departamento de Biología Funcional e Instituto Universitario de Oncología del Principado de Asturias, Universidad de Oviedo, 33006 Oviedo, Spain
| | - Gloria Blanco
- Departamento de Biología Funcional e Instituto Universitario de Oncología del Principado de Asturias, Universidad de Oviedo, 33006 Oviedo, Spain
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Raber ML, Castillo A, Greer A, Townsend CA. A conserved lysine in beta-lactam synthetase assists ring cyclization: Implications for clavam and carbapenem biosynthesis. Chembiochem 2010; 10:2904-12. [PMID: 19882698 DOI: 10.1002/cbic.200900389] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
beta-Lactam synthetase (beta-LS) is the paradigm of a growing class of enzymes that form the critical beta-lactam ring in the clavam and carbapenem antibiotics. beta-LS catalyzes a two-stage reaction in which N(2)-(2-carboxyethyl)-L-arginine is first adenylated, and then undergoes intramolecular ring closure. It was previously shown that the forward kinetic commitment to beta-lactam formation is high, and that the overall rate of reaction is partially limited to a protein conformational change rather than to the chemical step alone of closing the strained ring. beta-Lactam formation was evaluated on the basis of X-ray crystal structures, site-specific mutation, and kinetic and computational studies. The combined evidence clearly points to a reaction coordinate involving the formation of a tetrahedral transition state/intermediate stabilized by a conserved Lys. The combination of substrate preorganization, a well-stabilized transition state and an excellent leaving group facilitates this acyl substitution to account for the strong forward commitment to catalysis and to lower the barrier of four-membered ring formation to the magnitude of a protein conformational change.
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Affiliation(s)
- Mary L Raber
- Department of Chemistry, The Johns Hopkins University, Baltimore, MD 21218, USA
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28
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Rodríguez M, Méndez C, Salas JA, Blanco G. Transcriptional organization of ThnI-regulated thienamycin biosynthetic genes in Streptomyces cattleya. J Antibiot (Tokyo) 2010; 63:135-8. [DOI: 10.1038/ja.2009.133] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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29
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Bodner MJ, Phelan RM, Freeman MF, Li R, Townsend CA. Non-heme iron oxygenases generate natural structural diversity in carbapenem antibiotics. J Am Chem Soc 2010; 132:12-3. [PMID: 20017478 PMCID: PMC2821876 DOI: 10.1021/ja907320n] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Carbapenems are a clinically important antibiotic family. More than 50 naturally occurring carbapenam/ems are known and are distinguished primarily by their C-2/C-6 side chains where many are only differentiated by the oxidation states of these substituents. With a limited palette of variations the carbapenem family comprises a natural combinatorial library, and C-2/C-6 oxidation is associated with increased efficacy. We demonstrate that ThnG and ThnQ encoded by the thienamycin gene cluster in Streptomyces cattleya oxidize the C-2 and C-6 moieties of carbapenems, respectively. ThnQ stereospecifically hydroxylates PS-5 (5) giving N-acetyl thienamycin (2). ThnG catalyzes sequential desaturation and sulfoxidation of PS-5 (5), giving PS-7 (7) and its sulfoxide (9). The enzymes are relatively substrate selective but are proposed to give rise to the oxidative diversity of carbapenems produced by S. cattleya, and orthologues likely function similarly in allied streptomyces. Elucidating the roles of ThnG and ThnQ will focus further investigations of carbapenem antibiotic biosynthesis.
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Affiliation(s)
- Micah J. Bodner
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles St. Baltimore, MD 21218
| | - Ryan M. Phelan
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles St. Baltimore, MD 21218
| | - Michael F. Freeman
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles St. Baltimore, MD 21218
| | - Rongfeng Li
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles St. Baltimore, MD 21218
| | - Craig A. Townsend
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles St. Baltimore, MD 21218
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30
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Ducho C, Hamed RB, Batchelar ET, Sorensen JL, Odell B, Schofield CJ. Synthesis of regio- and stereoselectively deuterium-labelled derivatives of L-glutamate semialdehyde for studies on carbapenem biosynthesis. Org Biomol Chem 2009; 7:2770-9. [PMID: 19532994 DOI: 10.1039/b903312b] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
L-glutamate semialdehyde (L-GSA) is an intermediate in biosynthetic pathways including those leading to the carbapenem antibiotics. We describe studies on asymmetric deuteration or hydrogenation of appropriate didehydro-amino acid precursors for the stereoselective synthesis of C-2- and/or C-3-[2H]-labelled L-GSA suitable for use in mechanistic studies. Regioselective deuterium incorporation into the 5-position of L-GSA was achieved using a labelled form of the Schwartz reagent (Cp2Zr2HCl). 4,4-Dideuterated and fully backbone deuterated L-GSAs were prepared. The application of the labelled L-GSA derivatives to biosynthetic studies was exemplified by the chemo-enzymatic preparation of selectively deuterated trans-carboxymethylprolines using two different carboxymethylproline synthases (CarB and ThnE), enzymes that catalyse early steps in the biosynthesis of two carbapenems: (5R)-carbapenem-3-carboxylate and thienamycin, respectively.
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Affiliation(s)
- Christian Ducho
- University of Oxford, Department of Chemistry, Chemistry Research Laboratory, Mansfield Road, Oxford, United Kingdom OX1 3TA
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31
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Hamed RB, Batchelar ET, Mecinović J, Claridge TDW, Schofield CJ. Evidence that Thienamycin Biosynthesis Proceeds via C-5 Epimerization: ThnE Catalyzes the Formation of (2S,5S)-trans-Carboxymethylproline. Chembiochem 2009; 10:246-50. [DOI: 10.1002/cbic.200800652] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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