1
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Hagen A, Poust S, Rond TD, Fortman JL, Katz L, Petzold CJ, Keasling JD. Engineering a Polyketide Synthase for In Vitro Production of Adipic Acid. ACS Synth Biol 2016; 5:21-7. [PMID: 26501439 DOI: 10.1021/acssynbio.5b00153] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Polyketides have enormous structural diversity, yet polyketide synthases (PKSs) have thus far been engineered to produce only drug candidates or derivatives thereof. Thousands of other molecules, including commodity and specialty chemicals, could be synthesized using PKSs if composing hybrid PKSs from well-characterized parts derived from natural PKSs was more efficient. Here, using modern mass spectrometry techniques as an essential part of the design-build-test cycle, we engineered a chimeric PKS to enable production one of the most widely used commodity chemicals, adipic acid. To accomplish this, we introduced heterologous reductive domains from various PKS clusters into the borrelidin PKS' first extension module, which we previously showed produces a 3-hydroxy-adipoyl intermediate when coincubated with the loading module and a succinyl-CoA starter unit. Acyl-ACP intermediate analysis revealed an unexpected bottleneck at the dehydration step, which was overcome by introduction of a carboxyacyl-processing dehydratase domain. Appending a thioesterase to the hybrid PKS enabled the production of free adipic acid. Using acyl-intermediate based techniques to "debug" PKSs as described here, it should one day be possible to engineer chimeric PKSs to produce a variety of existing commodity and specialty chemicals, as well as thousands of chemicals that are difficult to produce from petroleum feedstocks using traditional synthetic chemistry.
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Affiliation(s)
| | | | | | | | | | - Christopher J. Petzold
- Physical
Bioscience Division, Lawrence Berkeley National Laboratory, Berkeley, California 94270, United States
| | - Jay D. Keasling
- Physical
Bioscience Division, Lawrence Berkeley National Laboratory, Berkeley, California 94270, United States
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2
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Annaval T, Paris C, Leadlay PF, Jacob C, Weissman KJ. Evaluating Ketoreductase Exchanges as a Means of Rationally Altering Polyketide Stereochemistry. Chembiochem 2015; 16:1357-64. [DOI: 10.1002/cbic.201500113] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2015] [Indexed: 12/22/2022]
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3
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Prasad G, Borketey LS, Lin TY, Schnarr NA. A mechanism-based fluorescence transfer assay for examining ketosynthase selectivity. Org Biomol Chem 2012; 10:6717-23. [PMID: 22806124 PMCID: PMC4232300 DOI: 10.1039/c2ob26008e] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Since their discovery, polyketide synthases have received massive attention from researchers hoping to harness their potential as a platform for generating new and improved therapeutics. Despite significant strides toward this end, inherent specificities within the enzymes responsible for polyketide production have severely limited these efforts. We have developed a mechanism-based, fluorescence transfer assay for a key enzyme component of all polyketide synthases, the ketosynthase domain. As demonstrated, this method can be used with both ketosynthase-containing didomains and full modules. As proof of principle, the ketosynthase domain from module 6 of the 6-deoxyerythronolide synthase is examined for its ability to accept a variety of simple thioester substrates. Consistent with its natural hexaketide substrate, we find that this ketosynthase prefers longer, α-branched thioesters and its ability to distinguish these structural features is quite remarkable. Substrate electronics are also tested via a variety of p-substituted aromatic groups. In all, we expect this technique to find considerable use in the field of polyketide biosynthesis and engineering due to its extraordinary simplicity and very distinct visible readout.
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Affiliation(s)
- Gitanjeli Prasad
- Department of Chemistry, University of Massachusetts, Amherst, 01003, USA
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4
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Crosby J, Crump MP. The structural role of the carrier protein--active controller or passive carrier. Nat Prod Rep 2012; 29:1111-37. [PMID: 22930263 DOI: 10.1039/c2np20062g] [Citation(s) in RCA: 131] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Common to all FASs, PKSs and NRPSs is a remarkable component, the acyl or peptidyl carrier protein (A/PCP). These take the form of small individual proteins in type II systems or discrete folded domains in the multi-domain type I systems and are characterized by a fold consisting of three major α-helices and between 60-100 amino acids. This protein is central to these biosynthetic systems and it must bind and transport a wide variety of functionalized ligands as well as mediate numerous protein-protein interactions, all of which contribute to efficient enzyme turnover. This review covers the structural and biochemical characterization of carrier proteins, as well as assessing their interactions with different ligands, and other synthase components. Finally, their role as an emerging tool in biotechnology is discussed.
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Affiliation(s)
- John Crosby
- School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK
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5
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Amoroso JW, Borketey LS, Prasad G, Schnarr NA. Direct acylation of carrier proteins with functionalized beta-lactones. Org Lett 2010; 12:2330-3. [PMID: 20433156 DOI: 10.1021/ol100684s] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
As the key component of many biosynthetic assemblies, acyl-carrier proteins offer a robust entry point for introduction of small molecule probes and pathway intermediates. Current labeling strategies primarily rely on modifications to the phosphopantetheine cofactor or its biosynthetic precursors followed by attachment to the apo form of a given carrier protein. As a greatly simplified alternative, direct and selective acylation of holo-acyl-carrier proteins using readily accessible beta-lactones as electrophilic partners for the phosphopantetheine-thiol has been demonstrated.
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Affiliation(s)
- Jon W Amoroso
- Department of Chemistry, University of Massachusetts, 710 North Pleasant Street, Amherst, Massachusetts 01003, USA
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6
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Tosin M, Betancor L, Stephens E, Ariel Li WM, Spencer JB, Leadlay PF. Synthetic Chain Terminators Off-Load Intermediates from a Type I Polyketide Synthase. Chembiochem 2010; 11:539-46. [DOI: 10.1002/cbic.200900772] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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7
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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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8
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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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9
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Zou Y, Yin J. Alkyne-functionalized chemical probes for assaying the substrate specificities of the adenylation domains in nonribosomal peptide synthetases. Chembiochem 2009; 9:2804-10. [PMID: 18988209 DOI: 10.1002/cbic.200800480] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Yekui Zou
- Department of Chemistry, The University of Chicago, 929 E. 57th Street, GCIS E505A, Chicago, IL 60637, USA
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10
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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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11
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Wu J, Hothersall J, Mazzetti C, O'Connell Y, Shields JA, Rahman AS, Cox RJ, Crosby J, Simpson TJ, Thomas CM, Willis CL. In vivo mutational analysis of the mupirocin gene cluster reveals labile points in the biosynthetic pathway: the "leaky hosepipe" mechanism. Chembiochem 2008; 9:1500-8. [PMID: 18465759 DOI: 10.1002/cbic.200800085] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
A common feature of the mupirocin and other gene clusters of the AT-less polyketide synthase (PKS) family of metabolites is the introduction of carbon branches by a gene cassette that contains a beta-hydroxy-beta-methylglutaryl CoA synthase (HMC) homologue and acyl carrier protein (ACP), ketosynthase (KS) and two crotonase superfamily homologues. In vivo studies of Pseudomonas fluorescens strains in which any of these components have been mutated reveal a common phenotype in which the two major isolable metabolites are the truncated hexaketide mupirocin H and the tetraketide mupiric acid. The structure of the latter has been confirmed by stereoselective synthesis. Mupiric acid is also the major metabolite arising from inactivation of the ketoreductase (KR) domain of module 4 of the modular PKS. A number of other mutations in the tailoring region of the mupirocin gene cluster also result in production of both mupirocin H and mupiric acid. To explain this common phenotype we propose a mechanistic rationale in which both mupirocin H and mupiric acid represent the products of selective and spontaneous release from labile points in the pathway that occur at significant levels when mutations block the pathway either close to or distant from the labile points.
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Affiliation(s)
- Ji'en Wu
- School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK
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12
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Tao L, Kiefer SE, Xie D, Bryson JW, Hefta SA, Doyle ML. Time-resolved limited proteolysis of mitogen-activated protein kinase-activated protein kinase-2 determined by LC/MS only. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2008; 19:841-854. [PMID: 18400511 DOI: 10.1016/j.jasms.2008.02.014] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2008] [Revised: 02/21/2008] [Accepted: 02/21/2008] [Indexed: 05/26/2023]
Abstract
Mass spectrometry has gained prominence in limited proteolysis studies largely due to its unparalleled precision in determining protein molecular mass. However, proteolytic fragments usually cannot be identified through direct mass measurement, since multiple subsequences of a protein can frequently be matched to observed masses of proteolytic fragments. Therefore, additional information from N-terminal sequencing is often needed. Here we demonstrate that mass spectrometry analysis of the time course of limited proteolysis reactions provides new information that is self-sufficient to identify all proteolytic fragments. The method uses a non-specific protease like subtilisin and exploits information contained in the time-resolved dataset such as: increased likelihood of identifying larger fragments generated during initial proteolysis solely by their masses, additivity of the masses of two mutually exclusive sequence regions that generate the full-length molecule (or an already assigned subfragment), and analyses of the proteolytic subfragment patterns that are facilitated by having established the initial cleavage sites. We show that the identities of the observed proteolytic fragments can be determined by LC/MS alone because enough constraints exist in the time-resolved dataset. For a medium-sized protein, it takes about 8 h to complete the study, a significant improvement over the traditional SDS-PAGE and N-terminal sequencing method, which usually takes several days. We illustrate this method with application to the catalytic domain of mitogen-activated protein kinase-activated protein kinase-2, and compare the results with N-terminal sequencing data and the known X-ray crystal structure.
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Affiliation(s)
- Li Tao
- Department of Gene Expression and Protein Biochemistry, Bristol-Myers Squibb Research and Development, Princeton, New Jersey 08534, USA.
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13
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Tran L, Tosin M, Spencer JB, Leadlay PF, Weissman KJ. Covalent linkage mediates communication between ACP and TE domains in modular polyketide synthases. Chembiochem 2008; 9:905-15. [PMID: 18348128 DOI: 10.1002/cbic.200700738] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Polyketide natural products such as erythromycin A and epothilone are assembled on multienzyme polyketide synthases (PKSs), which consist of modular sets of protein domains. Within these type I systems, the fidelity of biosynthesis depends on the programmed interaction among the multiple domains within each module, centered around the acyl carrier protein (ACP). A detailed understanding of interdomain communication will therefore be vital for attempts to reprogram these pathways by genetic engineering. We report here that the interaction between a representative ACP domain and its downstream thioesterase (TE) is mediated largely by covalent tethering through a short "linker" region, with only a minor energetic contribution from protein-protein molecular recognition. This finding helps explain in part the empirical observation that TE domains can function out of their normal context in engineered assembly lines, and supports the view that overall PKS architecture may dictate at least a subset of interdomain interactions.
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Affiliation(s)
- Lucky Tran
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, UK
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14
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Abstract
This review chronicles the synergistic growth of the fields of fatty acid and polyketide synthesis over the last century. In both animal fatty acid synthases and modular polyketide synthases, similar catalytic elements are covalently linked in the same order in megasynthases. Whereas in fatty acid synthases the basic elements of the design remain immutable, guaranteeing the faithful production of saturated fatty acids, in the modular polyketide synthases, the potential of the basic design has been exploited to the full for the elaboration of a wide range of secondary metabolites of extraordinary structural diversity.
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Affiliation(s)
- Stuart Smith
- Children's Hospital Oakland Research Institute, 5700 Martin Luther King Jr. Way, Oakland, California 94609, USA.
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15
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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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16
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Menzella HG, Reeves CD. Combinatorial biosynthesis for drug development. Curr Opin Microbiol 2007; 10:238-45. [PMID: 17553731 DOI: 10.1016/j.mib.2007.05.005] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2006] [Revised: 04/09/2007] [Accepted: 05/17/2007] [Indexed: 11/17/2022]
Abstract
Combinatorial biosynthesis can refer to any strategy for the genetic engineering of natural product biosynthesis to obtain new molecules, including the use of genetics for medicinal chemistry. However, it also implies the possibility that large libraries of complex compounds might be produced to feed a modern high-throughput screening operation. This review focuses on the multi-modular enzymes that produce polyketides, nonribosomal peptides, and hybrid polyketide-peptide compounds, which are the enzymes that appear to be most amenable to truly combinatorial approaches. The recent establishment of a high-throughput strategy for testing the activity of many non-natural combinations of modules from these enzymes should help speed the advance of this technology.
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Affiliation(s)
- Hugo G Menzella
- Kosan Biosciences, Inc. 3832 Bay Center Place, Hayward, CA 94545, USA
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17
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Richter CD, Stanmore DA, Miguel RN, Moncrieffe MC, Tran L, Brewerton S, Meersman F, Broadhurst RW, Weissman KJ. Autonomous folding of interdomain regions of a modular polyketide synthase. FEBS J 2007; 274:2196-209. [PMID: 17419733 DOI: 10.1111/j.1742-4658.2007.05757.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Domains within the multienzyme polyketide synthases are linked by noncatalytic sequences of variable length and unknown function. Recently, the crystal structure was reported of a portion of the linker between the acyltransferase (AT) and ketoreductase (KR) domains from module 1 of the erythromycin synthase (6-deoxyerythronolide B synthase), as a pseudodimer with the adjacent ketoreductase (KR). On the basis of this structure, the homologous linker region between the dehydratase (DH) and enoyl reductase (ER) domains in fully reducing modules has been proposed to occupy a position on the periphery of the polyketide synthases complex, as in porcine fatty acid synthase. We report here the expression and characterization of the same region of the 6-deoxyerythronolide B synthase module 1 AT-KR linker, without the adjacent KR domain (termed DeltaN AT1-KR1), as well as the corresponding section of the DH-ER linker. The linkers fold autonomously and are well structured. However, analytical gel filtration and ultracentrifugation analysis independently show that DeltaN AT1-KR1 is homodimeric in solution; site-directed mutagenesis further demonstrates that linker self-association is compatible with the formation of a linker-KR pseudodimer. Our data also strongly indicate that the DH-ER linker associates with the upstream DH domain. Both of these findings are incompatible with the proposed model for polyketide synthase architecture, suggesting that it is premature to allocate the linker regions to a position in the multienzymes based on the solved structure of animal fatty acid synthase.
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18
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Dorrestein PC, Bumpus SB, Calderone CT, Garneau-Tsodikova S, Aron ZD, Straight PD, Kolter R, Walsh CT, Kelleher NL. Facile detection of acyl and peptidyl intermediates on thiotemplate carrier domains via phosphopantetheinyl elimination reactions during tandem mass spectrometry. Biochemistry 2006; 45:12756-66. [PMID: 17042494 PMCID: PMC2518290 DOI: 10.1021/bi061169d] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
With the emergence of drug resistance and the genomic revolution, there has been a renewed interest in the genes that are responsible for the generation of bioactive natural products. Secondary metabolites of one major class are biosynthesized at one or more sites by ultralarge enzymes that carry covalent intermediates on phosphopantetheine arms. Because such intermediates are difficult to characterize in vitro, we have developed a new approach for streamlined detection of substrates, intermediates, and products attached to a phosphopantetheinyl arm of the carrier site. During vibrational activation of gas-phase carrier domains, facile elimination occurs in benchtop and Fourier-transform mass spectrometers alike. Phosphopantetheinyl ejections quickly reduce >100 kDa megaenzymes to <1000 Da ions for structural assignment of intermediates at <0.007 Da mass accuracy without proteolytic digestion. This "top down" approach quickly illuminated diverse acyl intermediates on the carrier domains of the nonribosomal peptide synthetases (NRPSs) or polyketide synthases (PKSs) found in the biosynthetic pathways of prodigiosin, pyoluteorin, mycosubtilin, nikkomycin, enterobactin, gramicidin, and several proteins from the orphan pksX gene cluster from Bacillus subtilis. By focusing on just those regions undergoing covalent chemistry, the method delivered clean proof for the reversible dehydration of hydroxymethylglutaryl-S-PksL via incorporation of 2H or 18O from the buffer. The facile nature of this revised assay will allow diverse laboratories to spearhead their NRPS-PKS projects with benchtop mass spectrometers.
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Affiliation(s)
- Pieter C. Dorrestein
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL, 600 S. Mathews Ave. 61801
| | - Stefanie B. Bumpus
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL, 600 S. Mathews Ave. 61801
| | - Christopher T. Calderone
- Department of Biological Chemistry & Molecular Pharmacology, Harvard Medical School, Boston, MA 02115
| | - Sylvie Garneau-Tsodikova
- Department of Biological Chemistry & Molecular Pharmacology, Harvard Medical School, Boston, MA 02115
| | - Zachary D. Aron
- Department of Biological Chemistry & Molecular Pharmacology, Harvard Medical School, Boston, MA 02115
| | - Paul D. Straight
- Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, MA 02115
| | - Roberto Kolter
- Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, MA 02115
| | - Christopher T. Walsh
- Department of Biological Chemistry & Molecular Pharmacology, Harvard Medical School, Boston, MA 02115
| | - Neil L. Kelleher
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL, 600 S. Mathews Ave. 61801
- Corresponding author: , Fax 217−244−8068, Phone 217−244−3927. Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL, 600 S. Mathews Ave. 61801
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Dorrestein PC, Blackhall J, Straight PD, Fischbach MA, Garneau-Tsodikova S, Edwards DJ, McLaughlin S, Lin M, Gerwick WH, Kolter R, Walsh CT, Kelleher NL. Activity screening of carrier domains within nonribosomal peptide synthetases using complex substrate mixtures and large molecule mass spectrometry. Biochemistry 2006; 45:1537-46. [PMID: 16460000 PMCID: PMC2565507 DOI: 10.1021/bi052333k] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
For screening a pool of potential substrates that load carrier domains found in nonribosomal peptide synthetases, large molecule mass spectrometry is shown to be a new, unbiased assay. Combining the high resolving power of Fourier transform mass spectrometry with the ability of adenylation domains to select their own substrates, the mass change that takes place upon formation of a covalent intermediate thus identifies the substrate. This assay has an advantage over traditional radiochemical assays in that many substrates, the substrate pool, can be screened simultaneously. Using proteins on the nikkomycin, clorobiocin, coumermycin A1, yersiniabactin, pyochelin, and enterobactin biosynthetic pathways as proof of principle, preferred substrates are readily identified from substrate pools. Furthermore, this assay can be used to provide insight into the timing of tailoring events of biosynthetic pathways as demonstrated using the bromination reaction found on the jamaicamide biosynthetic pathway. Finally, this assay can provide insight into the role and function of orphan gene clusters for which the encoded natural product is unknown. This is demonstrated by identifying the substrates for two NRPS modules from the pksN and pksJ genes that are found on an orphan NRPS/PKS hybrid cluster from Bacillus subtilis. This new assay format is especially timely for activity screening in an era when new types of thiotemplate assembly lines that defy classification are being discovered at an accelerating rate.
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Affiliation(s)
- Pieter C Dorrestein
- Department of Chemistry, University of Illinois, Urbana, Illinois 61801, USA
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20
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Hicks LM, Mazur MT, Miller LM, Dorrestein PC, Schnarr NA, Khosla C, Kelleher NL. Investigating Nonribosomal Peptide and Polyketide Biosynthesis by Direct Detection of Intermediates on >70 kDa Polypeptides by Using Fourier-Transform Mass Spectrometry. Chembiochem 2006; 7:904-7. [PMID: 16642537 DOI: 10.1002/cbic.200500416] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Leslie M Hicks
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, IL 61801, USA
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21
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Hicks LM, Moffitt MC, Beer LL, Moore BS, Kelleher NL. Structural characterization of in vitro and in vivo intermediates on the loading module of microcystin synthetase. ACS Chem Biol 2006; 1:93-102. [PMID: 17163649 DOI: 10.1021/cb500007v] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The microcystin family of toxins is the most common cause of hepatotoxicity associated with water blooms of cyanobacterial genera. The biosynthetic assembly line producing the toxic cyclic peptide, microcystin, contains an adenylation-peptidyl carrier protein didomain (A-PCP) at the N-terminus of the initiator module McyG (295 kDa) that has been postulated to activate and load the starter unit phenylacetate for formation of the unusual aromatic beta-amino acid residue, Adda, before subsequent extension. Characterization of the McyG A-PCP didomain (78 kDa) using ATP-PP i exchange assays and mass spectrometry revealed that assorted phenylpropanoids are preferentially activated and loaded onto the PCP carrier domain rather than phenylacetate itself. For the first time, thioesters formed in vivo were detected directly using large molecule mass spectrometry. Additionally substrates were cleaved using a type II thioesterase for structural elucidation by small molecule mass spectrometry. Unprecedented features of the McyG A-PCP didomain include the in vivo acylation of the holo PCP with exogenous and endogenous substrates, along with the ability of the apo protein to retain the acyl-AMP intermediate during affinity purification. These results imply that phenylpropanoids are preferentially loaded onto the McyG PCP; however one carbon must be excised following extension of the starter unit with malonyl-CoA in order to generate the expected polyketide chain which leads us to ponder the novel biochemistry by which this occurs.
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Affiliation(s)
- Leslie M Hicks
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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Dorrestein PC, Kelleher NL. Dissecting non-ribosomal and polyketide biosynthetic machineries using electrospray ionization Fourier-Transform mass spectrometry. Nat Prod Rep 2006; 23:893-918. [PMID: 17119639 DOI: 10.1039/b511400b] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Many virulence factors and bioactive compounds with antifungal, antimicrobial, and antitumor properties are produced via the non-ribosomal peptide synthetase (NRPS) or polyketide synthase(PKS) paradigm. During the biosynthesis of these natural products, substrates, intermediates and side products are covalently tethered to the NRPS or PKS catalyst, introducing mass changes, making these biosynthetic systems ideal candidates for interrogation by large molecule mass spectrometry. This review serves as an introduction into the application of electrospray ionization Fourier-Transform massspectrometry (ESI-FTMS) to investigate NRPS and PKS systems. ESI-FTMS can be used to understand substrate tolerance, timing of covalent linkages, timing of tailoring reactions and the transfer of substrates and biosynthetic intermediates from domain to domain. Therefore we not only highlight key mechanistic insights for thiotemplate systems as found on the enterobactin,yersiniabactin, epothilone, clorobiocin, coumermycin, pyoluteorin, gramicidin, mycosubtilin, C-1027,6-deoxyerythronolide B and FK520 biosynthetic pathways, but we also explain the approaches taken to identify active sites from complex digests and compare the FTMS based assay to traditional assays and other mass spectrometric techniques. Although mass spectrometry was introduced over two decades ago to investigate NRPS and PKS biosynthetic systems, this is the first review devoted to this methodology.
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Affiliation(s)
- Pieter C Dorrestein
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
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Schnarr NA, Chen AY, Cane DE, Khosla C. Analysis of covalently bound polyketide intermediates on 6-deoxyerythronolide B synthase by tandem proteolysis-mass spectrometry. Biochemistry 2005; 44:11836-42. [PMID: 16128585 DOI: 10.1021/bi0510781] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Polyketide natural products are biosynthesized via successive chain-elongation events mediated by elaborate protein assemblies. Facile detection of protein-bound intermediates in these systems will increase our understanding of enzyme reactivity and selectivity. We have developed a tandem proteolysis/mass spectrometric method for monitoring substrate loading and elongation in 6-deoxyerythronolide B synthase (DEBS), responsible for production of the macrolide precursor to erythromycin. Information regarding ketosynthase loading and polyketide unit elongation is readily acquired without need for complex protein or small molecule labels. A panel of structurally related substrates is evaluated through competition experiments and kinetic assays using LC-MS to resolve closely related species. Strong stereochemical effects are observed for ketosynthase substrate specificity. Semiquantitative kinetic analyses allow the resolution of the effects of structural and stereochemical changes on the individual ketosynthase-catalyzed steps of acyl-enzyme formation and polyketide chain extension.
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Affiliation(s)
- Nathan A Schnarr
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
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Kelleher NL, Hicks LM. Contemporary mass spectrometry for the direct detection of enzyme intermediates. Curr Opin Chem Biol 2005; 9:424-30. [PMID: 16129650 DOI: 10.1016/j.cbpa.2005.08.018] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2005] [Accepted: 08/16/2005] [Indexed: 11/28/2022]
Abstract
The field of enzymology has long used small-molecule mass spectrometry. However, the direct interrogation of covalent and non-covalent intermediates by large-molecule mass spectrometry of enzymes or large peptide substrates is illuminating an increasingly diverse array of chemistries used in nature. Recent advances now allow improved detection of several modifications formed at sub-stoichiometric levels on the same polypeptide, and elucidation of intermediate dynamics with low millisecond temporal resolution. Highlighting recent applications in both ribosomal and non-ribosomal biosynthesis of natural products, along with acetyl transferases, sulfonucleotide reducatases, and PEP-utilizing enzymes, the utility of small- and large-molecule mass spectrometry to reveal enzyme intermediates and illuminate mechanism is described briefly. From ever more complex mixtures, mass spectrometry continues to evolve into a key technology for a larger number of today's enzymologists.
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Affiliation(s)
- Neil L Kelleher
- Department of Chemistry, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA.
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