1
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Serapian S, Crosby J, Crump MP, van der Kamp MW. Path to Actinorhodin: Regio- and Stereoselective Ketone Reduction by a Type II Polyketide Ketoreductase Revealed in Atomistic Detail. JACS AU 2022; 2:972-984. [PMID: 35557750 PMCID: PMC9088766 DOI: 10.1021/jacsau.2c00086] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Revised: 03/15/2022] [Accepted: 03/16/2022] [Indexed: 06/15/2023]
Abstract
In type II polyketide synthases (PKSs), which typically biosynthesize several antibiotic and antitumor compounds, the substrate is a growing polyketide chain, shuttled between individual PKS enzymes, while covalently tethered to an acyl carrier protein (ACP): this requires the ACP interacting with a series of different enzymes in succession. During biosynthesis of the antibiotic actinorhodin, produced by Streptomyces coelicolor, one such key binding event is between an ACP carrying a 16-carbon octaketide chain (actACP) and a ketoreductase (actKR). Once the octaketide is bound inside actKR, it is likely cyclized between C7 and C12 and regioselective reduction of the ketone at C9 occurs: how these elegant chemical and conformational changes are controlled is not yet known. Here, we perform protein-protein docking, protein NMR, and extensive molecular dynamics simulations to reveal a probable mode of association between actACP and actKR; we obtain and analyze a detailed model of the C7-C12-cyclized octaketide within the actKR active site; and we confirm this model through multiscale (QM/MM) reaction simulations of the key ketoreduction step. Molecular dynamics simulations show that the most thermodynamically stable cyclized octaketide isomer (7R,12R) also gives rise to the most reaction competent conformations for ketoreduction. Subsequent reaction simulations show that ketoreduction is stereoselective as well as regioselective, resulting in an S-alcohol. Our simulations further indicate several conserved residues that may be involved in selectivity of C7-12 cyclization and C9 ketoreduction. Detailed insights obtained on ACP-based substrate presentation in type II PKSs can help design ACP-ketoreductase systems with altered regio- or stereoselectivity.
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Affiliation(s)
- Stefano
A. Serapian
- School
of Biochemistry, University of Bristol, University Walk, Bristol BS8 1TD, United Kingdom
| | - John Crosby
- School
of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, United Kingdom
| | - Matthew P. Crump
- School
of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, United Kingdom
| | - Marc W. van der Kamp
- School
of Biochemistry, University of Bristol, University Walk, Bristol BS8 1TD, United Kingdom
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2
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Thiocysteine lyases as polyketide synthase domains installing hydropersulfide into natural products and a hydropersulfide methyltransferase. Nat Commun 2021; 12:5672. [PMID: 34584078 PMCID: PMC8479088 DOI: 10.1038/s41467-021-25798-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2021] [Accepted: 09/01/2021] [Indexed: 12/02/2022] Open
Abstract
Nature forms S-S bonds by oxidizing two sulfhydryl groups, and no enzyme installing an intact hydropersulfide (-SSH) group into a natural product has been identified to date. The leinamycin (LNM) family of natural products features intact S-S bonds, and previously we reported an SH domain (LnmJ-SH) within the LNM hybrid nonribosomal peptide synthetase (NRPS)-polyketide synthase (PKS) assembly line as a cysteine lyase that plays a role in sulfur incorporation. Here we report the characterization of an S-adenosyl methionine (SAM)-dependent hydropersulfide methyltransferase (GnmP) for guangnanmycin (GNM) biosynthesis, discovery of hydropersulfides as the nascent products of the GNM and LNM hybrid NRPS-PKS assembly lines, and revelation of three SH domains (GnmT-SH, LnmJ-SH, and WsmR-SH) within the GNM, LNM, and weishanmycin (WSM) hybrid NRPS-PKS assembly lines as thiocysteine lyases. Based on these findings, we propose a biosynthetic model for the LNM family of natural products, featuring thiocysteine lyases as PKS domains that directly install a -SSH group into the GNM, LNM, or WSM polyketide scaffold. Genome mining reveals that SH domains are widespread in Nature, extending beyond the LNM family of natural products. The SH domains could also be leveraged as biocatalysts to install an -SSH group into other biologically relevant scaffolds. Enzymes installing an intact hydropersulfide (-SSH) group into natural products have so far not been identified. Here, the authors report the characterization of an S-adenosyl methionine-dependent hydropersulfide methyltransferase (GnmP) for guangnanmycin biosynthesis, and identification of three SH domains within several NRPS-PKS assembly lines as thiocysteine lyases.
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3
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Drufva EE, Spengler NR, Hix EG, Bailey CB. Site-Directed Mutagenesis of Modular Polyketide Synthase Ketoreductase Domains for Altered Stereochemical Control. Chembiochem 2020; 22:1122-1150. [PMID: 33185924 DOI: 10.1002/cbic.202000613] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Revised: 11/12/2020] [Indexed: 12/18/2022]
Abstract
Bacterial modular type I polyketide synthases (PKSs) are complex multidomain assembly line proteins that produce a range of pharmaceutically relevant molecules with a high degree of stereochemical control. Due to their colinear properties, they have been considerable targets for rational biosynthetic pathway engineering. Among the domains harbored within these complex assembly lines, ketoreductase (KR) domains have been extensively studied with the goal of altering their stereoselectivity by site-directed mutagenesis, as they confer much of the stereochemical complexity present in pharmaceutically active reduced polyketide scaffolds. Here we review all efforts to date to perform site-directed mutagenesis on PKS KRs, most of which have been done in the context of excised KR domains on model diffusible substrates such as β-keto N-acetyl cysteamine thioesters. We also discuss the challenges around translating the findings of these studies to alter stereocontrol in the context of a complex multidomain enzymatic assembly line.
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Affiliation(s)
- Erin E Drufva
- Department of Chemistry, University of Tennessee, Knoxville, Knoxville, TN 37996, USA
| | - Nolan R Spengler
- Department of Chemistry, University of Tennessee, Knoxville, Knoxville, TN 37996, USA
| | - Elijah G Hix
- Department of Chemistry, University of Tennessee, Knoxville, Knoxville, TN 37996, USA
| | - Constance B Bailey
- Department of Chemistry, University of Tennessee, Knoxville, Knoxville, TN 37996, USA
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4
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Cogan DP, Li X, Sevillano N, Mathews II, Matsui T, Craik CS, Khosla C. Antibody Probes of Module 1 of the 6-Deoxyerythronolide B Synthase Reveal an Extended Conformation During Ketoreduction. J Am Chem Soc 2020; 142:14933-14939. [PMID: 32786753 DOI: 10.1021/jacs.0c05133] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The 6-deoxyerythronolide B synthase (DEBS) is a prototypical assembly line polyketide synthase (PKS) that synthesizes the macrocyclic core of the antibiotic erythromycin. Each of its six multidomain modules presumably sample distinct conformations, as biosynthetic intermediates tethered to their acyl carrier proteins interact with multiple active sites during the courses of their catalytic cycles. The spatiotemporal details underlying these protein dynamics remain elusive. Here, we investigate one aspect of this conformational flexibility using two domain-specific monoclonal antibody fragments (Fabs) isolated from a very large naïve human antibody library. Both Fabs, designated 1D10 and 2G10, were bound specifically and with high affinity to the ketoreductase domain of DEBS module 1 (KR1). Comparative kinetic analysis of stand-alone KR1 as well as a truncated bimodular derivative of DEBS revealed that 1D10 inhibited KR1 activity whereas 2G10 did not. Co-crystal structures of each KR1-Fab complex provided a mechanistic rationale for this difference. A hybrid PKS module harboring KR1 was engineered, whose individual catalytic domains have been crystallographically characterized at high resolution. Size exclusion chromatography coupled to small-angle X-ray scattering (SEC-SAXS) of this hybrid module bound to 1D10 provided further support for the catalytic relevance of the "extended" model of a PKS module. Our findings reinforce the power of monoclonal antibodies as tools to interrogate structure-function relationships of assembly line PKSs.
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Affiliation(s)
| | | | - Natalia Sevillano
- Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California 94158, United States
| | - Irimpan I Mathews
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Tsutomu Matsui
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Charles S Craik
- Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California 94158, United States
| | - Chaitan Khosla
- Chemical Engineering, Stanford University, Stanford, California 94305, United States.,Stanford ChEM-H, Stanford University, Stanford, California 94305, United States
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5
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Serapian SA, van der Kamp MW. Unpicking the Cause of Stereoselectivity in Actinorhodin Ketoreductase Variants with Atomistic Simulations. ACS Catal 2019. [DOI: 10.1021/acscatal.8b04846] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Stefano A. Serapian
- School of Biochemistry, University of Bristol, University Walk, Bristol, BS8 1TD, United Kingdom
| | - Marc W. van der Kamp
- School of Biochemistry, University of Bristol, University Walk, Bristol, BS8 1TD, United Kingdom
- Centre for Computational Chemistry, University of Bristol, Cantock’s
Close, Bristol, BS8 1TS, United Kingdom
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6
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Moretto L, Vance S, Heames B, Broadhurst RW. Dissecting how modular polyketide synthase ketoreductases interact with acyl carrier protein-attached substrates. Chem Commun (Camb) 2017; 53:11457-11460. [PMID: 28980673 PMCID: PMC6038798 DOI: 10.1039/c7cc04625a] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Accepted: 06/29/2017] [Indexed: 11/21/2022]
Abstract
Interaction studies using fragments excised from the modular mycolactone polyketide synthase show that ketoreductase domains possess a generic binding site for acyl carrier protein domains and provide evidence that the pendant 5'-phosphopantetheine prosthetic group plays a key role in delivering acyl substrates to the active site in the correct orientation.
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Affiliation(s)
- Luisa Moretto
- Department of Molecular Biosciences
, The University of Texas at Austin
,
Austin
, TX 78712
, USA
| | - Steven Vance
- Crescendo Biologics Ltd
,
Meditrina Building 260
, Babraham Research Campus
, Cambridge CB22 3AT
, UK
| | - Brennan Heames
- Department of Biochemistry
, University of Cambridge
,
80 Tennis Court Road
, Cambridge CB2 1GA
, UK
.
| | - R. William Broadhurst
- Department of Biochemistry
, University of Cambridge
,
80 Tennis Court Road
, Cambridge CB2 1GA
, UK
.
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7
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Weissman KJ. Polyketide stereocontrol: a study in chemical biology. Beilstein J Org Chem 2017; 13:348-371. [PMID: 28326145 PMCID: PMC5331325 DOI: 10.3762/bjoc.13.39] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Accepted: 02/01/2017] [Indexed: 11/23/2022] Open
Abstract
The biosynthesis of reduced polyketides in bacteria by modular polyketide synthases (PKSs) proceeds with exquisite stereocontrol. As the stereochemistry is intimately linked to the strong bioactivity of these molecules, the origins of stereochemical control are of significant interest in attempts to create derivatives of these compounds by genetic engineering. In this review, we discuss the current state of knowledge regarding this key aspect of the biosynthetic pathways. Given that much of this information has been obtained using chemical biology tools, work in this area serves as a showcase for the power of this approach to provide answers to fundamental biological questions.
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Affiliation(s)
- Kira J Weissman
- UMR 7365, Ingénierie Moléculaire et Physiopathologie Articulaire (IMoPA), CNRS-Université de Lorraine, Biopôle de l’Université de Lorraine, Campus Biologie Santé, Avenue de la Forêt de Haye, BP 50184, 54505 Vandœuvre-lès-Nancy Cedex, France
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8
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Bailey CB, Pasman ME, Keatinge-Clay AT. Substrate structure-activity relationships guide rational engineering of modular polyketide synthase ketoreductases. Chem Commun (Camb) 2016; 52:792-5. [PMID: 26568113 PMCID: PMC4690787 DOI: 10.1039/c5cc07315d] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Modular polyketide synthase ketoreductases can set two chiral centers through a single reduction. To probe the basis of stereocontrol, a structure-activity relationship study was performed with three α-methyl, β-ketothioester substrates and four ketoreductases. Since interactions with the β-ketoacyl moiety were found to be most critical, residues implicated in contacting this moiety were mutated. Two mutations were sufficient to completely reverse the stereoselectivity of the model ketoreductase EryKR1, converting it from an enzyme that generates (2S,3R)-products into one that yields (2S,3S)-products.
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Affiliation(s)
- Constance B Bailey
- Department of Chemistry, University of Texas at Austin, 105 E. 24th St. Stop A5300, Austin, TX 78712, USA.
| | - Marjolein E Pasman
- Department of Chemistry, University of Texas at Austin, 105 E. 24th St. Stop A5300, Austin, TX 78712, USA.
| | - Adrian T Keatinge-Clay
- Department of Chemistry, University of Texas at Austin, 105 E. 24th St. Stop A5300, Austin, TX 78712, USA. and Department of Molecular Biosciences, University of Texas at Austin, 2506 Speedway Stop A5000, Austin, TX 78712, USA
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9
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Wang H, Zhang H, Zou Y, Mi Y, Lin S, Xie Z, Yan Y, Zhang H. Structural Insight into the Tetramerization of an Iterative Ketoreductase SiaM through Aromatic Residues in the Interfaces. PLoS One 2014; 9:e97996. [PMID: 24901639 PMCID: PMC4046962 DOI: 10.1371/journal.pone.0097996] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Accepted: 04/23/2014] [Indexed: 11/19/2022] Open
Affiliation(s)
- Hua Wang
- Key Laboratory of Molecular Biophysics, Ministry of Education, Wuhan, Hubei, China
- Department of Biotechnology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Huaidong Zhang
- Key Laboratory of Molecular Biophysics, Ministry of Education, Wuhan, Hubei, China
- Department of Biotechnology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Yi Zou
- State Key Laboratory of Microbial Metabolism, School of Life Sciences & Biotechnology, Shanghai Jiao Tong University, Shanghai, China
| | - Yanling Mi
- Key Laboratory of Molecular Biophysics, Ministry of Education, Wuhan, Hubei, China
- Department of Biotechnology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Shuangjun Lin
- State Key Laboratory of Microbial Metabolism, School of Life Sciences & Biotechnology, Shanghai Jiao Tong University, Shanghai, China
| | - Zhixiong Xie
- College of Life Sciences, Wuhan University, Wuhan, Hubei, China
| | - Yunjun Yan
- Key Laboratory of Molecular Biophysics, Ministry of Education, Wuhan, Hubei, China
- Department of Biotechnology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Houjin Zhang
- Key Laboratory of Molecular Biophysics, Ministry of Education, Wuhan, Hubei, China
- Department of Biotechnology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
- * E-mail:
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10
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Soehano I, Yang L, Ding F, Sun H, Low ZJ, Liu X, Liang ZX. Insights into the programmed ketoreduction of partially reducing polyketide synthases: stereo- and substrate-specificity of the ketoreductase domain. Org Biomol Chem 2014; 12:8542-9. [DOI: 10.1039/c4ob01777c] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Evidence are provided to support that partially reducing polyketide synthases achieve programmed ketoreduction by differential recognition of polyketide intermediates.
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Affiliation(s)
- Ishin Soehano
- School of Biological Sciences Nanyang Technological University
- , Singapore
| | - Lifeng Yang
- School of Biological Sciences Nanyang Technological University
- , Singapore
| | - Feiqing Ding
- School of Mathematics and Physics
- Nanyang Technological University
- , Singapore
| | - Huihua Sun
- School of Biological Sciences Nanyang Technological University
- , Singapore
| | - Zhen Jie Low
- School of Biological Sciences Nanyang Technological University
- , Singapore
| | - Xuewei Liu
- School of Mathematics and Physics
- Nanyang Technological University
- , Singapore
| | - Zhao-Xun Liang
- School of Biological Sciences Nanyang Technological University
- , Singapore
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11
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Agnew DE, Pfleger BF. Synthetic biology strategies for synthesizing polyhydroxyalkanoates from unrelated carbon sources. Chem Eng Sci 2013; 103:58-67. [DOI: 10.1016/j.ces.2012.12.023] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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12
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Javidpour P, Bruegger J, Srithahan S, Korman TP, Crump MP, Crosby J, Burkart MD, Tsai SC. The determinants of activity and specificity in actinorhodin type II polyketide ketoreductase. ACTA ACUST UNITED AC 2013; 20:1225-34. [PMID: 24035284 DOI: 10.1016/j.chembiol.2013.07.016] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2011] [Revised: 06/28/2013] [Accepted: 07/07/2013] [Indexed: 11/17/2022]
Abstract
In the actinorhodin type II polyketide synthase, the first polyketide modification is a regiospecific C9-carbonyl reduction, catalyzed by the ketoreductase (actKR). Our previous studies identified the actKR 94-PGG-96 motif as a determinant of stereospecificity. The molecular basis for reduction regiospecificity is, however, not well understood. In this study, we examined the activities of 20 actKR mutants through a combination of kinetic studies, PKS reconstitution, and structural analyses. Residues have been identified that are necessary for substrate interaction, and these observations have suggested a structural model for this reaction. Polyketides dock at the KR surface and are steered into the enzyme pocket where C7-C12 cyclization is mediated by the KR before C9-ketoreduction can occur. These molecular features can potentially serve as engineering targets for the biosynthesis of novel, reduced polyketides.
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Affiliation(s)
- Pouya Javidpour
- Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA 92697, USA
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13
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Zhang Q, Pang B, Ding W, Liu W. Aromatic Polyketides Produced by Bacterial Iterative Type I Polyketide Synthases. ACS Catal 2013. [DOI: 10.1021/cs400211x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Qi Zhang
- State Key
Laboratory of Bioorganic and Natural Products Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy
of Sciences, 345 Lingling Road, Shanghai 200032, China
| | - Bo Pang
- State Key
Laboratory of Bioorganic and Natural Products Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy
of Sciences, 345 Lingling Road, Shanghai 200032, China
| | - Wei Ding
- State Key
Laboratory of Bioorganic and Natural Products Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy
of Sciences, 345 Lingling Road, Shanghai 200032, China
| | - Wen Liu
- State Key
Laboratory of Bioorganic and Natural Products Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy
of Sciences, 345 Lingling Road, Shanghai 200032, China
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14
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Kitsche A, Kalesse M. Configurational Assignment of Secondary Hydroxyl Groups and Methyl Branches in Polyketide Natural Products through Bioinformatic Analysis of the Ketoreductase Domain. Chembiochem 2013; 14:851-61. [DOI: 10.1002/cbic.201300063] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2013] [Indexed: 12/17/2022]
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15
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Sun H, Ho CL, Ding F, Soehano I, Liu XW, Liang ZX. Synthesis of (R)-Mellein by a Partially Reducing Iterative Polyketide Synthase. J Am Chem Soc 2012; 134:11924-7. [DOI: 10.1021/ja304905e] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Huihua Sun
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive,
Singapore 637551
| | - Chun Loong Ho
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive,
Singapore 637551
| | - Feiqing Ding
- School
of Mathematics and Physics, Nanyang Technological University, 21 Nanyang Link, Singapore 637371
| | - Ishin Soehano
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive,
Singapore 637551
| | - Xue-Wei Liu
- School
of Mathematics and Physics, Nanyang Technological University, 21 Nanyang Link, Singapore 637371
| | - Zhao-Xun Liang
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive,
Singapore 637551
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16
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Javidpour P, Das A, Khosla C, Tsai SC. Structural and biochemical studies of the hedamycin type II polyketide ketoreductase (HedKR): molecular basis of stereo- and regiospecificities. Biochemistry 2011; 50:7426-39. [PMID: 21776967 DOI: 10.1021/bi2006866] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Bacterial aromatic polyketides that include many antibiotic and antitumor therapeutics are biosynthesized by the type II polyketide synthase (PKS), which consists of 5-10 stand-alone enzymatic domains. Hedamycin, an antitumor antibiotic polyketide, is uniquely primed with a hexadienyl group generated by a type I PKS followed by coupling to a downstream type II PKS to biosynthesize a 24-carbon polyketide, whose C9 position is reduced by hedamycin type II ketoreductase (hedKR). HedKR is homologous to the actinorhodin KR (actKR), for which we have conducted extensive structural studies previously. How hedKR can accommodate a longer polyketide substrate than the actKR, and the molecular basis of its regio- and stereospecificities, is not well understood. Here we present a detailed study of hedKR that sheds light on its specificity. Sequence alignment of KRs predicts that hedKR is less active than actKR, with significant differences in substrate/inhibitor recognition. In vitro and in vivo assays of hedKR confirmed this hypothesis. The hedKR crystal structure further provides the molecular basis for the observed differences between hedKR and actKR in the recognition of substrates and inhibitors. Instead of the 94-PGG-96 motif observed in actKR, hedKR has the 92-NGG-94 motif, leading to S-dominant stereospecificity, whose molecular basis can be explained by the crystal structure. Together with mutations, assay results, docking simulations, and the hedKR crystal structure, a model for the observed regio- and stereospecificities is presented herein that elucidates how different type II KRs recognize substrates with different chain lengths, yet precisely reduce only the C9-carbonyl group. The molecular features of hedKR important for regio- and stereospecificities can potentially be applied to biosynthesize new polyketides via protein engineering that rationally controls polyketide ketoreduction.
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Affiliation(s)
- Pouya Javidpour
- Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, California 92697, United States
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17
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Kwan DH, Schulz F. The stereochemistry of complex polyketide biosynthesis by modular polyketide synthases. Molecules 2011; 16:6092-115. [PMID: 21775938 PMCID: PMC6264292 DOI: 10.3390/molecules16076092] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2011] [Revised: 07/06/2011] [Accepted: 07/18/2011] [Indexed: 11/24/2022] Open
Abstract
Polyketides are a diverse class of medically important natural products whose biosynthesis is catalysed by polyketide synthases (PKSs), in a fashion highly analogous to fatty acid biosynthesis. In modular PKSs, the polyketide chain is assembled by the successive condensation of activated carboxylic acid-derived units, where chain extension occurs with the intermediates remaining covalently bound to the enzyme, with the growing polyketide tethered to an acyl carrier domain (ACP). Carboxylated acyl-CoA precursors serve as activated donors that are selected by the acyltransferase domain (AT) providing extender units that are added to the growing chain by condensation catalysed by the ketosynthase domain (KS). The action of ketoreductase (KR), dehydratase (DH), and enoylreductase (ER) activities can result in unreduced, partially reduced, or fully reduced centres within the polyketide chain depending on which of these enzymes are present and active. The PKS-catalysed assembly process generates stereochemical diversity, because carbon–carbon double bonds may have either cis- or trans- geometry, and because of the chirality of centres bearing hydroxyl groups (where they are retained) and branching methyl groups (the latter arising from use of propionate extender units). This review shall cover the studies that have determined the stereochemistry in many of the reactions involved in polyketide biosynthesis by modular PKSs.
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Affiliation(s)
- David H. Kwan
- Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver B.C., V6T 1Z1, Canada
- Authors to whom correspondence should be addressed; (D.H.K.); (F.S.); Tel.: +1-604-822-9300 (D.H.K.); +49-231-133-2429 (F.S.); Fax: +1-604-822-9126 (D.H.K.); +49-231-133-2498 (F.S.)
| | - Frank Schulz
- Fakultät für Chemie, Chemische Biologie, Technische Universität Dortmund, Otto-Hahn-Straße 6, 44221 Dortmund, Germany
- Max-Planck-Institut für Molekulare Physiologie, Abteilung für Chemische Biologie, Otto-Hahn- Straße 11, 44227 Dortmund, Germany
- Authors to whom correspondence should be addressed; (D.H.K.); (F.S.); Tel.: +1-604-822-9300 (D.H.K.); +49-231-133-2429 (F.S.); Fax: +1-604-822-9126 (D.H.K.); +49-231-133-2498 (F.S.)
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18
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Javidpour P, Korman TP, Shakya G, Tsai SC. Structural and biochemical analyses of regio- and stereospecificities observed in a type II polyketide ketoreductase. Biochemistry 2011; 50:4638-49. [PMID: 21506596 DOI: 10.1021/bi200335f] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Type II polyketides include antibiotics such as tetracycline and chemotherapeutics such as daunorubicin. Type II polyketides are biosynthesized by the type II polyketide synthase (PKS) that consists of 5-10 stand-alone domains. In many type II PKSs, the type II ketoreductase (KR) specifically reduces the C9-carbonyl group. How the type II KR achieves such a high regiospecificity and the nature of stereospecificity are not well understood. Sequence alignment of KRs led to a hypothesis that a well-conserved 94-XGG-96 motif may be involved in controlling the stereochemistry. The stereospecificity of single-, double-, and triple-mutant combinations of P94L, G95D, and G96D were analyzed in vitro and in vivo for the actinorhodin KR (actKR). The P94L mutation is sufficient to change the stereospecificity of actKR. Binary and ternary crystal structures of both wild-type and P94L actKR were determined. Together with assay results, docking simulations, and cocrystal structures, a model for stereochemical control is presented herein that elucidates how type II polyketides are introduced into the substrate pocket such that the C9-carbonyl can be reduced with high regio- and stereospecificities. The molecular features of actKR important for regio- and stereospecificities can potentially be applied in biosynthesizing new polyketides via protein engineering that rationally controls polyketide keto reduction.
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Affiliation(s)
- Pouya Javidpour
- Department of Molecular Biology and Biochemistry, University of California-Irvine, CA 92697, USA
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19
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Kwan DH, Tosin M, Schläger N, Schulz F, Leadlay PF. Insights into the stereospecificity of ketoreduction in a modular polyketide synthase. Org Biomol Chem 2011; 9:2053-6. [DOI: 10.1039/c1ob00022e] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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20
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Cane DE. Programming of erythromycin biosynthesis by a modular polyketide synthase. J Biol Chem 2010; 285:27517-23. [PMID: 20522551 DOI: 10.1074/jbc.r110.144618] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Affiliation(s)
- David E Cane
- Department of Chemistry, Brown University, Providence, Rhode Island 02912-9108, USA.
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21
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Valenzano CR, Lawson RJ, Chen AY, Khosla C, Cane DE. The biochemical basis for stereochemical control in polyketide biosynthesis. J Am Chem Soc 2009; 131:18501-11. [PMID: 19928853 PMCID: PMC3699857 DOI: 10.1021/ja908296m] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
One of the most striking features of complex polyketides is the presence of numerous methyl- and hydroxyl-bearing stereogenic centers. To investigate the biochemical basis for the control of polyketide stereochemistry and to establish the timing and mechanism of the epimerization at methyl-bearing centers, a series of incubations was carried out using reconstituted components from a variety of modular polyketide synthases. In all cases the stereochemistry of the product was directly correlated with the intrinsic stereospecificity of the ketoreductase domain, independent of the particular chain elongation domains that were used, thereby establishing that methyl group epimerization, when it does occur, takes place after ketosynthase-catalyzed chain elongation. The finding that there were only minor differences in the rates of product formation observed for parallel incubations using an epimerizing ketoreductase domain and the nonepimerizing ketoreductase domain supports the proposal that the epimerization is catalyzed by the ketoreductase domain itself.
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Affiliation(s)
- Chiara R. Valenzano
- Department of Chemistry, Box H, Brown University, Providence, Rhode Island 02912-9108
| | - Rachel J. Lawson
- Department of Chemistry, Box H, Brown University, Providence, Rhode Island 02912-9108
| | - Alice Y. Chen
- Department of Chemical Engineering, Stanford University, Stanford, California 94305
| | - Chaitan Khosla
- Department of Chemical Engineering, Stanford University, Stanford, California 94305
- Department of Chemistry, Stanford University, Stanford, California 94305
- Department of Biochemistry, Stanford University, Stanford, California 94305
| | - David E. Cane
- Department of Chemistry, Box H, Brown University, Providence, Rhode Island 02912-9108
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22
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Hong H, Leadlay PF, Staunton J. The changing patterns of covalent active site occupancy during catalysis on a modular polyketide synthase multienzyme revealed by ion-trap mass spectrometry. FEBS J 2009; 276:7057-69. [PMID: 19860832 DOI: 10.1111/j.1742-4658.2009.07418.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
A catalytically competent, homodimeric diketide synthase comprising the first extension module of the erythromycin polyketide synthase was analysed using MS, after limited proteolysis to release functional domains, to determine the pattern of covalent attachment of substrates and intermediates to active sites during catalysis. Using the natural substrates, the acyltransferase and acylcarrier protein of the loading module were found to be heavily loaded with propionyl starter groups, while the ketosynthase was fully propionylated. The acylcarrier protein of the extension module was partly occupied by the product diketide, and the adjacent chain-releasing thioesterase domain was vacant, implying that the rate-limiting step is transfer of the diketide from the acylcarrier protein to the thioesterase domain. The data suggest an attractive model for preventing iterative chain extension by efficient repriming of the ketosynthase domain after condensation. Use of the alternative starter unit valeryl-CoA produced an altered pattern, in which a significant proportion of the extension acylcarrier protein was loaded with methylmalonate, not diketide, consistent with the condensation step having become an additional slow step. Strikingly, when NADPH was omitted, the extension acylcarrier protein contained methylmalonate and none of the expected keto diketide, in contrast to results obtained previously by mixing individual recombinant domains, showing the importance of also studying intact modules. The detailed patterns of loading of the extension acylcarrier protein (of which there are two in the homodimer) also provided the first evidence for simultaneous loading of both acylcarrier proteins and for the coordination of timing between the two active centres for chain extension.
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Affiliation(s)
- Hui Hong
- Department of Chemistry, University of Cambridge, UK.
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23
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Strieter ER, Koglin A, Aron ZD, Walsh CT. Cascade reactions during coronafacic acid biosynthesis: elongation, cyclization, and functionalization during Cfa7-catalyzed condensation. J Am Chem Soc 2009; 131:2113-5. [PMID: 19199623 PMCID: PMC2662718 DOI: 10.1021/ja8077945] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Herein, the biogenesis of the hydrindane ring system within coronafacic acid (CFA) has been investigated. These studies reveal that in addition to the canonical polyketide chain elongation and functionalization encoded by type I polyketide synthase (PKSs), cascade reactions can take place during assembly line-like biosynthesis. Indeed, upon Cfa7-catalyzed Claisen condensation between enzyme-bound malonate and an N-acetylcysteamine (SNAC) thioester, latent reactivity within the elongated enzyme-bound intermediate is unveiled. This reactivity translates into an intramolecular cyclization, which can proceed in a facile manner as observed by the enzyme-independent cyclization of a linear beta-ketothioester intermediate.
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Affiliation(s)
- Eric R Strieter
- Harvard Medical School, Department of Biological Chemistry and Molecular Pharmacology, 240 Longwood Avenue, Boston, Massachusetts 02115, USA
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24
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Betancor L, Fernández MJ, Weissman KJ, Leadlay PF. Improved catalytic activity of a purified multienzyme from a modular polyketide synthase after coexpression with Streptomyces chaperonins in Escherichia coli. Chembiochem 2009; 9:2962-6. [PMID: 19021139 DOI: 10.1002/cbic.200800475] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Lorena Betancor
- Department of Biochemistry, University of Cambridge, Cambridge, UK
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25
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Kellenberger L, Galloway IS, Sauter G, Böhm G, Hanefeld U, Cortés J, Staunton J, Leadlay PF. A polylinker approach to reductive loop swaps in modular polyketide synthases. Chembiochem 2009; 9:2740-9. [PMID: 18937219 DOI: 10.1002/cbic.200800332] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Multiple versions of the DEBS 1-TE gene, which encodes a truncated bimodular polyketide synthase (PKS) derived from the erythromycin-producing PKS, were created by replacing the DNA encoding the ketoreductase (KR) domain in the second extension module by either of two synthetic oligonucleotide linkers. This made available a total of nine unique restriction sites for engineering. The DNA for donor "reductive loops," which are sets of contiguous domains comprising either KR or KR and dehydratase (DH), or KR, DH and enoylreductase (ER) domains, was cloned from selected modules of five natural PKS multienzymes and spliced into module 2 of DEBS 1-TE using alternative polylinker sites. The resulting hybrid PKSs were tested for triketide production in vivo. Most of the hybrid multienzymes were active, vindicating the treatment of the reductive loop as a single structural unit, but yields were dependent on the restriction sites used. Further, different donor reductive loops worked optimally with different splice sites. For those reductive loops comprising DH, ER and KR domains, premature TE-catalysed release of partially reduced intermediates was sometimes seen, which provided further insight into the overall stereochemistry of reduction in those modules. Analysis of loops containing KR only, which should generate stereocentres at both C-2 and C-3, revealed that the 3-hydroxy configuration (but not the 2-methyl configuration) could be altered by appropriate choice of a donor loop. The successful swapping of reductive loops provides an interesting parallel to a recently suggested pathway for the natural evolution of modular PKSs by recombination.
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Affiliation(s)
- Laurenz Kellenberger
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB21GA, United Kingdom
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26
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Abstract
This chapter describes structural and associated enzymological studies of polyketide synthases, including isolated single domains and multidomain fragments. The sequence-structure-function relationship of polyketide biosynthesis, compared with homologous fatty acid synthesis, is discussed in detail. Structural enzymology sheds light on sequence and structural motifs that are important for the precise timing, substrate recognition, enzyme catalysis, and protein-protein interactions leading to the extraordinary structural diversity of naturally occurring polyketides.
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27
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Korman TP, Tan YH, Wong J, Luo R, Tsai SC. Inhibition kinetics and emodin cocrystal structure of a type II polyketide ketoreductase. Biochemistry 2008; 47:1837-47. [PMID: 18205400 DOI: 10.1021/bi7016427] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Type II polyketides are a class of natural products that include pharmaceutically important aromatic compounds such as the antibiotic tetracycline and antitumor compound doxorubicin. The type II polyketide synthase (PKS) is a complex consisting of 5-10 standalone domains homologous to fatty acid synthase (FAS). Polyketide ketoreductase (KR) provides regio- and stereochemical diversity during the reduction. How the type II polyketide KR specifically reduces only the C9 carbonyl group is not well understood. The cocrystal structures of actinorhodin polyketide ketoreductase (actKR) bound with NADPH or NADP+ and the inhibitor emodin were solved with the wild type and P94L mutant of actKR, revealing the first observation of a bent p-quinone in an enzyme active site. Molecular dynamics simulation help explain the origin of the bent geometry. Extensive screening for in vitro substrates shows that unlike FAS KR, the actKR prefers bicyclic substrates. Inhibition kinetics indicate that actKR follows an ordered Bi Bi mechanism. Together with docking simulations that identified a potential phosphopantetheine binding groove, the structural and functional studies reveal that the C9 specificity is a result of active site geometry and substrate ring constraints. The results lay the foundation for the design of novel aromatic polyketide natural products with different reduction patterns.
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Affiliation(s)
- Tyler Paz Korman
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697, USA
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28
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Castonguay R, He W, Chen AY, Khosla C, Cane DE. Stereospecificity of ketoreductase domains of the 6-deoxyerythronolide B synthase. J Am Chem Soc 2007; 129:13758-69. [PMID: 17918944 PMCID: PMC2547127 DOI: 10.1021/ja0753290] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
6-Deoxyerythronolide B synthase (DEBS) is a modular polyketide synthase (PKS) responsible for the biosynthesis of 6-dEB (1), the parent aglycone of the broad spectrum macrolide antibiotic erythromycin. Individual DEBS modules, which contain the catalytic domains necessary for each step of polyketide chain elongation and chemical modification, can be deconstructed into constituent domains. To better understand the intrinsic stereospecificity of the ketoreductase (KR) domains, an in vitro reconstituted system has been developed involving combinations of ketosynthase (KS)-acyl transferase (AT) didomains with acyl-carrier protein (ACP) and KR domains from different DEBS modules. Incubations with (2S,3R)-2-methyl-3-hydroxypentanoic acid N-acetylcysteamine thioester (2) and methylmalonyl-CoA plus NADPH result in formation of a reduced, ACP-bound triketide that is converted to the corresponding triketide lactone 4 by either base- or enzyme-catalyzed hydrolysis/cyclization. A sensitive and robust GC-MS technique has been developed to assign the stereochemistry of the resulting triketide lactones, on the basis of direct comparison with synthetic standards of each of the four possible diasteromers 4a-4d. Using the [KS][AT] didomains from either DEBS module 3 or module 6 in combination with KR domains from modules 2 or 6 gave in all cases exclusively (2R,3S,4R,5R)-3,5-dihydroxy-2,4-dimethyl-n-heptanoic acid-delta-lactone (4a). The same product was also generated by a chimeric module in which [KS3][AT3] was fused to [KR5][ACP5] and the DEBS thioesterase [TE] domain. Reductive quenching of the ACP-bound 2-methyl-3-ketoacyl triketide intermediate with sodium borohydride confirmed that in each case the triketide intermediate carried only an unepimerized d-2-methyl group. The results confirm the predicted stereospecificity of the individual KR domains, while revealing an unexpected configurational stability of the ACP-bound 2-methyl-3-ketoacyl thioester intermediate. The methodology should be applicable to the study of any combination of heterologous [KS][AT] and [KR] domains.
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Affiliation(s)
- Roselyne Castonguay
- Contribution from the Department of Chemistry, Box H, Brown University, Providence, Rhode Island 02912-9108
| | - Weiguo He
- Contribution from the Department of Chemistry, Box H, Brown University, Providence, Rhode Island 02912-9108
| | - Alice Y. Chen
- Department of Chemical Engineering, Stanford University, Stanford, California 94305
| | - Chaitan Khosla
- Department of Chemical Engineering, Stanford University, Stanford, California 94305
- Department of Chemistry, Stanford University, Stanford, California 94305
- Department of Biochemistry, Stanford University, Stanford, California 94305
| | - David E. Cane
- Contribution from the Department of Chemistry, Box H, Brown University, Providence, Rhode Island 02912-9108
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29
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Abstract
6-Deoxyerythronolide B, the macrocyclic aglycone of the antibiotic erythromycin, is synthesized by a polyketide synthase (PKS) that has emerged as the prototypical modular megasynthase. A variety of molecular biological, protein chemical, and biosynthetic experiments over the past two decades have yielded insights into its mechanistic features. More recently, high-resolution structural images of portions of the 6-deoxyerythronolide B synthase have provided a platform for interpreting this wealth of biochemical data, while at the same time presenting a fundamentally new basis for the design of more detailed investigations into this remarkable enzyme. For example, the critical roles of domain-domain interactions and nonconserved linkers, as well as large interdomain movements in the structure and function of modular PKSs, have been highlighted. In turn, these insights point the way forward for more sophisticated and efficient biosynthetic engineering of complex polyketide natural products.
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Affiliation(s)
- Chaitan Khosla
- Department of Chemical Engineering, Stanford University, Stanford, California 94305, USA.
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30
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Bali S, O'Hare HM, Weissman KJ. Broad substrate specificity of ketoreductases derived from modular polyketide synthases. Chembiochem 2006; 7:478-84. [PMID: 16453348 DOI: 10.1002/cbic.200500430] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Recombinant ketoreductase (KR) domains derived from antibiotic-producing modular polyketide synthases (PKSs) have been examined as potential catalysts for the enantioselective reduction of non-polyketide substrates. KR domains from two modular PKSs show significant activity toward alternative substrates, particularly those that incorporate cyclohexyl moieties. Through site-directed mutagenesis of the amino acid motifs previously implicated in stereocontrol by KRs, we have identified mutants with improved activity toward such compounds. These results suggest that PKS KRs could potentially be used as biotransformation catalysts for the production of chiral alcohols.
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Affiliation(s)
- Shilpa Bali
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, UK
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31
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Baerga-Ortiz A, Popovic B, Siskos AP, O'Hare HM, Spiteller D, Williams MG, Campillo N, Spencer JB, Leadlay PF. Directed Mutagenesis Alters the Stereochemistry of Catalysis by Isolated Ketoreductase Domains from the Erythromycin Polyketide Synthase. ACTA ACUST UNITED AC 2006; 13:277-85. [PMID: 16638533 DOI: 10.1016/j.chembiol.2006.01.004] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2005] [Revised: 01/10/2006] [Accepted: 01/10/2006] [Indexed: 11/18/2022]
Abstract
The ketoreductase (KR) domains eryKR(1) and eryKR(2) from the erythromycin-producing polyketide synthase (PKS) reduce 3-ketoacyl-thioester intermediates with opposite stereospecificity. Modeling of eryKR(1) and eryKR(2) showed that conserved amino acids previously correlated with production of alternative alcohol configurations lie in the active site. eryKR(1) domains mutated at these positions showed an altered stereochemical outcome in reduction of (2R, S)-2-methyl-3-oxopentanoic acid N-acetylcysteamine thioester. The wild-type eryKR(1) domain exclusively gave the (2S, 3R)-3-hydroxy-2-methylpentanoic acid N-acetylcysteamine thioester, while the double mutant (F141W, P144G) gave only the (2S, 3S) isomer, a switch of the alcohol stereochemistry. Mutation of the eryKR(2) domain, in contrast, greatly increased the proportion of the wild-type (2R, 3S)-alcohol product. These data confirm the role of key residues in stereocontrol and suggest an additional way to make rational alterations in polyketide antibiotic structure.
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Affiliation(s)
- Abel Baerga-Ortiz
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, United Kingdom
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32
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O'Hare HM, Baerga-Ortiz A, Popovic B, Spencer JB, Leadlay PF. High-Throughput Mutagenesis to Evaluate Models of Stereochemical Control in Ketoreductase Domains from the Erythromycin Polyketide Synthase. ACTA ACUST UNITED AC 2006; 13:287-96. [PMID: 16638534 DOI: 10.1016/j.chembiol.2006.01.003] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2005] [Revised: 12/21/2005] [Accepted: 01/06/2006] [Indexed: 11/25/2022]
Abstract
Ketoreductase (KR) activities help determine the stereochemistry of the products of modular polyketide synthases (PKSs). For example, domains eryKR(1) and eryKR(2), contained, respectively, in the first and second extension modules of the erythromycin-producing PKS, reduce 3-ketoacyl-thioester intermediates with opposite stereospecificity. Amino acid motifs that correlate with stereochemical outcome have been identified in KRs. We have used saturation mutagenesis of these motifs in eryKR(1) and eryKR(2), and a microplate-based screen of such mutants for activity against (9R, S)-trans-1-decalone, to identify candidate enzymes potentially altered in stereocontrol. Active mutants were reassayed with (2R, S)-2-methyl-3-oxopentanoic acid N-acetylcysteamine thioester, and the alcohol products were analyzed by chiral HPLC. Variant enzymes were found with either altered substrate selectivity for the (2R) or (2S) substrate or altered stereospecificity of reduction, or both, further highlighting the importance of these motifs in stereochemical control.
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Affiliation(s)
- Helen M O'Hare
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, United Kingdom
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33
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Abstract
In this issue of Chemistry & Biology, Leadlay and coworkers report overproduction of a number of ketoreductase domains from modular polyketide synthases. These discrete enzymes allow the stereochemistry of polyketide ketoreduction to be studied in isolation.
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Affiliation(s)
- Patrick Caffrey
- School of Biomolecular and Biomedical Science and Centre for Synthesis and Chemical Biology, University College Dublin, Ireland
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34
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Hill AM. The biosynthesis, molecular genetics and enzymology of the polyketide-derived metabolites. Nat Prod Rep 2005; 23:256-320. [PMID: 16572230 DOI: 10.1039/b301028g] [Citation(s) in RCA: 121] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
This review covers the biosynthesis of aliphatic and aromatic polyketides as well as mixed polyketide/NRPS metabolites, and discusses the molecular genetics and enzymology of the proteins responsible for their formation.
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35
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Siskos AP, Baerga-Ortiz A, Bali S, Stein V, Mamdani H, Spiteller D, Popovic B, Spencer JB, Staunton J, Weissman KJ, Leadlay PF. Molecular Basis of Celmer's Rules: Stereochemistry of Catalysis by Isolated Ketoreductase Domains from Modular Polyketide Synthases. ACTA ACUST UNITED AC 2005; 12:1145-53. [PMID: 16242657 DOI: 10.1016/j.chembiol.2005.08.017] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2005] [Revised: 08/01/2005] [Accepted: 08/01/2005] [Indexed: 10/25/2022]
Abstract
A system is reported for the recombinant expression of individual ketoreductase (KR) domains from modular polyketide synthases (PKSs) and scrutiny of their intrinsic specificity and stereospecificity toward surrogate diketide substrates. The eryKR(1) and the tylKR(1) domains, derived from the first extension module of the erythromycin PKS and the tylosin PKS, respectively, both catalyzed reduction of (2R, S)-2-methyl-3-oxopentanoic acid N-acetylcysteamine thioester, with complete stereoselectivity and stereospecificity, even though the substrate is not tethered to an acyl carrier protein or an intact PKS multienzyme. In contrast, and to varying degrees, the isolated enzymes eryKR(2), eryKR(5), and eryKR(6) exercised poorer control over substrate selection and the stereochemical course of ketoreduction. These data, together with modeling of diketide binding to KR(1) and KR(2), demonstrate the fine energetic balance between alternative modes of presentation of ketoacylthioester substrates to KR active sites.
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36
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Hong H, Appleyard AN, Siskos AP, Garcia-Bernardo J, Staunton J, Leadlay PF. Chain initiation on type I modular polyketide synthases revealed by limited proteolysis and ion-trap mass spectrometry. FEBS J 2005; 272:2373-87. [PMID: 15885088 DOI: 10.1111/j.1742-4658.2005.04615.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Limited proteolysis in combination with liquid chromatography-ion trap mass spectrometry (LC-MS) was used to analyze engineered or natural proteins derived from a type I modular polyketide synthase (PKS), the 6-deoxyerythronolide B synthase (DEBS), and comprising either the first two extension modules linked to the chain-terminating thioesterase (TE) (DEBS1-TE); or the last two extension modules (DEBS3) or the first extension module linked to TE (diketide synthase, DKS). Functional domains were released by controlled proteolysis, and the exact boundaries of released domains were obtained through mass spectrometry and N-terminal sequencing analysis. The acyltransferase-acyl carrier protein required for chain initiation (AT(L)-ACP(L)), was released as a didomain from both DEBS1-TE and DKS, as well as the off-loading TE as a didomain with the adjacent ACP. Mass spectrometry was used successfully to monitor in detail both the release of individual domains, and the patterns of acylation of both intact and digested DKS when either propionyl-CoA or n-butyryl-CoA were used as initiation substrates. In particular, both loading domains and the ketosynthase domain of the first extension module (KS1) were directly observed to be simultaneously primed. The widely available and simple MS methodology used here offers a convenient approach to the proteolytic mapping of PKS multienzymes and to the direct monitoring of enzyme-bound intermediates.
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Affiliation(s)
- Hui Hong
- Department of Chemistry, University of Cambridge, UK
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37
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Hadfield AT, Limpkin C, Teartasin W, Simpson TJ, Crosby J, Crump MP. The Crystal Structure of the actIII Actinorhodin Polyketide Reductase. Structure 2004; 12:1865-75. [PMID: 15458634 DOI: 10.1016/j.str.2004.08.002] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2004] [Accepted: 08/02/2004] [Indexed: 11/20/2022]
Abstract
We have determined the 2.5 angstroms crystal structure of an active, tetrameric Streptomyces coelicolor type II polyketide ketoreductase (actIII) with its bound cofactor, NADP+. This structure shows a Rossman dinucleotide binding fold characteristic of SDR enzymes. Of two subunits in the crystallographic asymmetric unit, one is closed around the active site. Formate is observed in the open subunit, indicating possible carbonyl binding sites of the polyketide intermediate. Unlike previous models we observe crystal contacts that may mimic the KR-ACP interactions that may drive active site opening. Based on these observations, we have constructed a model for ACP and polyketide binding. We propose that binding of ACP triggers a conformational change from the closed to the open, active form of the enzyme. The polyketide chain enters the active site and reduction occurs. The model also suggests a general mechanism for ACP recognition which is applicable to a range of protein families.
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Affiliation(s)
- Andrea T Hadfield
- Department of Biochemistry, University of Bristol, School of Medical Sciences, University Walk, Bristol, BS8 1TD, United Kingdom.
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38
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Abstract
Combinatorial biosynthesis involves the genetic manipulation of natural product biosynthetic enzymes to produce potential new drug candidates that would otherwise be difficult to obtain. In either a theoretical or practical sense, the number of combinations possible from different types of natural product pathways ranges widely. Enzymes that have been the most amenable to this technology synthesize the polyketides, nonribosomal peptides, and hybrids of the two. The number of polyketide or peptide natural products theoretically possible is huge, but considerable work remains before these large numbers can be realized. Nevertheless, many analogs have been created by this technology, providing useful structure-activity relationship data and leading to a few compounds that may reach the clinic in the next few years. In this review the focus is on recent advances in our understanding of how different enzymes for natural product biosynthesis can be used successfully in this technology.
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39
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Abstract
Polyketides are a large class of structurally diverse, biologically active natural products. Recent experiments add evidence that many of the enzymes involved in the biosynthesis of these natural products are intrinsically tolerant of nonnatural substrates. In addition, an increasing understanding of structure-function relationships in various enzyme-substrate systems is aiding efforts to begin engineering these proteins for even greater synthetic utility.
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Affiliation(s)
- Nicola L Pohl
- Department of Chemistry and the Plant Sciences Institute, 2756 Gilman Hall, Iowa State University, Ames, IA 50011-3111, USA.
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