Christopher Walsh

Christopher Walsh
Harvard Medical School | HMS · Department of Biological Chemistry and Molecular Pharmacology

PhD

About

311
Publications
31,224
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33,435
Citations
Citations since 2017
2 Research Items
11417 Citations
201720182019202020212022202305001,0001,500
201720182019202020212022202305001,0001,500
201720182019202020212022202305001,0001,500
201720182019202020212022202305001,0001,500

Publications

Publications (311)
Article
Macrocycles are appealing drug candidates due to their high-affinity, specificity, and favorable pharmacological properties. In this study, we explored the effects of chemical modifications to a natural product macrocycle upon its activity, 3D geometry, and conformational entropy. We chose thiocillin as a model system, a thiopeptide in the ribosoma...
Article
Significance Here we investigate the structural basis for cyclization activity in hybrid polyketide synthase-nonribosomal peptide synthetases. This first structure of a cyclization (Cy) domain reveals an unexpected location for the enzyme active site, providing a fresh perspective on past mutational studies. Our structures also depict two 20-Å-long...
Article
The soil actinomycete Kutzneria sp. 744 produces a class of highly decorated hexadepsipeptides, which represent a new chemical scaffold that has both antimicrobial and antifungal properties. These natural products, known as kutznerides, are created via nonribosomal peptide synthesis using various derivatized amino acids. The piperazic acid moiety c...
Article
Full-text available
Covering: up to 2014Dithiolopyrrolone (DTP) group antibiotics were first isolated in the early half of the 20th century, but only recently has research been reawakened by insights gained from the synthesis and biosynthesis of this structurally intriguing class of molecules. DTPs are characterized by an electronically unique bicyclic structure, whic...
Article
Two hallmarks of assembly line polyketide synthases have motivated an interest in these unusual multi-enzyme systems - their stereospecificity and the capacity for directional biosynthesis. In this review, we summarize the state of knowledge regarding the mechanistic origins of these two remarkable features, using the 6-deoxyerythronolide B synthas...
Article
The bimodular 276 kDa nonribosomal peptide synthetase AspA from Aspergillus alliaceus, heterologously expressed in Saccharomyces cerevisiae, converts tryptophan and two molecules of the aromatic β-amino acid anthranilate (Ant) into a pair of tetracyclic peptidyl alkaloids asperlicin C and D in a ratio of 10:1. The first module of AspA activates and...
Article
Freestanding nonproteinogenic amino acids have long been recognized for their antimetabolite properties and tendency to be uncovered to reactive functionalities by the catalytic action of target enzymes. By installing them regiospecifically into biogenic peptides and proteins, it may be possible to usher a new era at the interface between small mol...
Article
Frei vorkommende nichtproteinogene Aminosäuren sind schon lange wegen ihrer antimetabolen Eigenschaften bekannt. Entdeckt werden sie meist aufgrund der Reaktivität gegenüber der katalytischen Wirkung der Zielenzyme. Führt man sie regiospezifisch in biogene Peptide und Proteine ein, kann es möglich werden, eine neue Ära der Medizinalchemie an der Gr...
Article
There is a continuous need for iterative cycles of antibiotic discovery and development to deal with the selection of resistant pathogens that emerge as therapeutic application of an antibiotic becomes widespread. A short golden age of antibiotic discovery from nature followed by a subsequent golden half century of medicinal chemistry optimization...
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Berninamycin is a member of the pyridine-containing thiopeptide class of antibiotics that undergoes massive posttranslational modifications from ribosomally generated preproteins. Berninamycin has a 2-oxazolyl-3-thiazolyl-pyridine core embedded in a 35-atom macrocycle rather than typical trithiazolylpyridine cores embedded in 26-atom and 29-atom pe...
Article
The echinocandins are a small group of fungal N-acylated cyclic hexapeptides that are fungicidal for candida strains and fungistatic for aspergilli by targeting cell wall 1,3-β-glucan synthases. The side chains of all six amino acid building blocks have hydroxyl groups, including the nonproteinogenic 4R,5R-dihydroxy-Orn1, 4R-OH-Pro3, 3S, 4S-dihydro...
Article
Ardeemins are hexacyclic peptidyl alkaloids isolated from Aspergillus fischeri as agents that block efflux of anticancer drugs by (MultiDrug Resistance) MDR export pumps. To evaluate the biosynthetic logic and enzymatic machinery for ardeemin framework assembly, we sequenced the A. fischeri genome and identified the ardABC gene cluster. Through bot...
Article
Thiopeptide antibiotics exhibit a profound level of chemical diversity that is installed through cascades of posttranslational modifications on ribosomal peptides. Here, we present a technique to rapidly explore the chemical space of the thiopeptide GE37468 through codon randomization, yielding insights into thiopeptide maturation as well as struct...
Article
Biosynthesis of the dithiolopyrrolone antibiotic holomycin in Streptomyces clavuligerus involves the closure of a pair of enethiols to a cyclic disulfide. We have shown that the dithiol oxidase HlmI is responsible for the disulfide formation and this enzyme also plays a role in self-protection. In the present study, we examine how S. clavuligerus d...
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Full-text available
Covering: 1988 to 2012This review presents recommended nomenclature for the biosynthesis of ribosomally synthesized and post-translationally modified peptides (RiPPs), a rapidly growing class of natural products. The current knowledge regarding the biosynthesis of the >20 distinct compound classes is also reviewed, and commonalities are discussed.
Article
Members of the asperlicin family of fungal metabolites produced by Aspergillus alliaceus are known potent CCK(A) antagonists. Herein, we report the identification of the gene cluster responsible for directing their biosynthesis. We validate and probe the pathway by genetic manipulation, and provide the first biochemical characterization of the oxid...
Article
Echinocandins are a family of fungal lipidated cyclic hexapeptide natural products. Due to their effectiveness as antifungal agents, three semisynthetic derivatives have been developed and approved for treatment of human invasive candidiasis. All six of the amino acid residues are hydroxylated, including 4R,5R-dihydroxy-L-ornithine, 4R-hydroxyl-L-p...
Article
The indolocarbazole biosynthetic enzymes StaC, InkE, RebC, and AtmC mediate the degree of oxidation of chromopyrrolic acid on route to the natural products staurosporine, K252a, rebeccamycin, and AT2433-A1, respectively. Here, we show that StaC and InkE, which mediate a net 4-electron oxidation, bind FAD with a micromolar K(d), whereas RebC and Atm...
Article
The thiocillins from Bacillus cereus ATCC 14579 are natural products from the broader class of thiazolyl peptides. Their biosynthesis proceeds via extensive post-translational modification of a ribosomally encoded precursor peptide. This post-translational tailoring involves a key step formal cycloaddition between two distal serine residues. In the...
Article
Which came first? We have investigated the biosynthesis of the piperazic acid (Piz) building blocks in the kutzneride family of metabolites. The flavin-dependent oxygenase KtzI was shown to convert ornithine to N(5)-OH-Orn. LC-MS/MS showed (13)C(5)-labeled versions of these two amino acids to be direct precursors of piperazic acid in vivo.
Article
Nitrogen heterocycles are the key functional and structural elements in both RNA and DNA, in half a dozen of the most important coenzymes, and in many synthetic drug scaffolds. On the other hand, only 3 of 20 proteinogenic amino acids have nitrogen heterocycles: proline, histidine, and tryptophan. This inventory can be augmented in microbial protei...
Article
Polyketide synthases (PKSs) and non-ribosomal peptide synthetases (NRPSs) are large multidomain proteins present in microorganisms that produce bioactive compounds. Curacin A is such a bioactive compound with potent anti-proliferative activity. During its biosynthesis the growing substrate is bound covalently to an acyl carrier protein (ACP) that i...
Article
2,5-Dihydrophenylalanine (H(2)Phe) is a multipotent nonproteinogenic amino acid produced by various Actinobacteria and Gammaproteobacteria. Although the metabolite was discovered over 40 years ago, details of its biosynthesis have remained largely unknown. We show here that L-H(2)Phe is a secreted metabolite in Photorhabdus luminescens cultures and...
Article
Xenematide, a cyclic depsipeptide antibiotic produced by Xenorhabdus nematophila, had a candidate nonribosomal peptide synthetase (NRPS) with atypical features. Differential metabolite analysis between a mutant and wildtype validated that this stand-alone NRPS was required for xenematide production, and further analysis led to a series of new xenem...
Article
Peptidyl nucleoside antibiotics are a group of natural products targeting MraY, a bacterial translocase involved in the lipid-linked cycle in peptidoglycan biosynthesis. In this Perspective, we explore how Nature builds complex peptidyl nucleoside antibiotics scaffolds from simple nucleoside and amino acid building blocks. We discuss the current st...
Article
Thiazolyl peptides are bacterial secondary metabolites that potently inhibit protein synthesis in Gram-positive bacteria and malarial parasites. Recently, our laboratory and others reported that this class of trithiazolyl pyridine-containing natural products is derived from ribosomally synthesized preproteins that undergo a cascade of posttranslati...
Article
The enzymatic activation of 3,4-dehydrolysine and subsequent formation of the 12-membered syringolin macrolactam were investigated. The timing of the desaturation was elucidated through the analysis of the initial adenylation domain of SylD. The SylD-TTE didomain was characterized and demonstrated to be the catalyst for formation of 12-membered mac...
Article
Pacidamycins are a family of uridyl tetra/pentapeptide antibiotics with antipseudomonal activities through inhibition of the translocase MraY in bacterial cell wall assembly. The biosynthetic gene cluster for pacidamycins has recently been identified through genome mining of the producer Streptomyces coeruleorubidus, and the highly dissociated nonr...
Article
Kutznerides 2 and 8 of the cyclic hexadepsipeptide family of antifungal natural products from the soil actinomycete Kutzneria sp. 744 contain two sets of chlorinated residues, a 6,7-dichlorohexahydropyrroloindole moiety derived from dichlorotryptophan and a 5-chloropiperazate moiety, as well as a methylcyclopropylglycine residue that may arise from...
Article
The dapdiamides make up a family of antibiotics that have been presumed to be cleaved in the target cell to enzyme-inhibitory N-acyl-2,3-diaminopropionate (DAP) warheads containing two alternative electrophilic moieties. Our prior biosynthetic studies revealed that an eneamide warhead is made first and converted to an epoxyamide via a three-enzyme...
Article
Pacidamycins are a family of uridyl peptide antibiotics that inhibit the translocase MraY, an essential enzyme in bacterial cell wall biosynthesis that to date has not been clinically targeted. The pacidamycin structural skeleton contains a doubly inverted peptidyl chain with a β-peptide and a ureido linkage as well as a 3'-deoxyuridine nucleoside...
Article
Non-ribosomal peptide synthetases (NRPSs) are multi-module, multi-domain enzymes, synthesizing a wealth of important natural products in bacteria and fungi. These products often find pharmaceutical applications as antibiotics, antitumor agents or immunosuppressant drugs. NRPS use a remarkable assembly line organization to covalently load substrates...
Article
The gene cluster from Pantoea agglomerans responsible for biosynthesis of the dapdiamide antibiotics encodes an adenylation-thiolation didomain protein, DdaD, and an Fe(II)/α-ketoglutarate-dependent dioxygenase homologue, DdaC. Here we show that DdaD, a nonribosomal peptide synthetase module, activates and sequesters N(β)-fumaramoyl-l-2,3-diaminopr...
Article
Prephenate is the direct precursor of phenylpyruvate and 4-hydroxyphenylpyruvate in the biogenesis of phenylalanine and tyrosine by action of the decarboxylative, aromatizing enzymes prephenate dehydratase and dehydrogenase, respectively. The recent characterization of BacA in bacilysin biosynthesis as a nonaromatizing decarboxylase reveals a new r...
Article
Nonribosomal peptide synthetase (NRPS) assembly lines are major avenues for the biosynthesis of a vast array of peptidyl natural products. Several hundred bacterial NRPS gene clusters contain a small (∼70-residue) protein belonging to the MbtH family for which no function has been defined. Here we show that two strictly conserved Trp residues in Mb...
Article
Glidobactins are hybrid NRPS-PKS natural products that function as irreversible proteasome inhibitors. A variety of medium chain 2(E),4(E)-diene fatty acids N-acylate the peptidolactam core and contribute significantly to the potency of proteasome inhibition. We have expressed the initiation NRPS module GlbF (C-A-T) in Escherichia coli and observe...
Article
Full-text available
Pacidamycins are a family of uridyl tetra/pentapeptide antibiotics that act on the translocase MraY to block bacterial cell wall assembly. To elucidate the biosynthetic logic of pacidamcyins, a putative gene cluster was identified by 454 shotgun genome sequencing of the producer Streptomyces coeruleorubidus NRRL 18370. The 31-kb gene cluster encode...
Article
The pyridine core of the thiocillins has long been postulated to arise from a late-stage tail-to-tail condensation of two dehydroalanines. Genetic disruption of tclM, a proposed "Diels-Alderase", allowed isolation of acyclic precursors to this pyridine ring. The isolated products possess the full cohort of post-translational modifications that are...
Article
Full-text available
Antibiotics of the thiocillin, GE2270A, and thiostrepton class, which block steps in bacterial protein synthesis, contain a trithiazolyl (tetrahydro)pyridine core that provides the architectural constraints for high affinity binding to either the 50 S ribosomal subunit or elongation factor Tu. These mature antibiotic scaffolds arise from a cascade...
Article
The enzymes DdaG and DdaF, encoded in the Pantoea agglomerans dapdiamide antibiotic biosynthetic gene cluster, when expressed in Escherichia coli, form the tandem amide bonds of the dapdiamide scaffold at the expense of ATP cleavage. DdaG uses fumarate, 2,3-diaminopropionate (DAP), and ATP to make fumaroyl-AMP transiently on the way to the N(beta)-...
Article
Bacillus cereus ATCC 14579 converts the C-terminal 14 residues of a 52-mer prepeptide into a related set of eight variants of the thiocillin subclass of thiazolyl peptide antibiotics by a cascade of post-translational modifications that alter 13 of those 14 residues. We have introduced prepeptide gene variants into a knockout strain to conduct an a...
Article
A number of natural products contain a 2-amino-3-hydroxycyclopent-2-enone five membered ring, termed C(5)N, which is condensed via an amide linkage to a variety of polyketide-derived polyenoic acid scaffolds. Bacterial genome mining indicates three tandem ORFs that may be involved in C(5)N formation and subsequent installation in amide linkages. We...
Article
Natural products have played a prominent role in the history of organic chemistry, and they continue to be important as drugs, biological probes, and targets of study for synthetic and analytical chemists. In this Perspective, we explore how connecting Nature's small molecules to the genes that encode them has sparked a renaissance in natural produ...
Article
Full-text available
Fungal natural products containing benzodiazepinone- and quinazolinone-fused ring systems can be assembled by nonribosomal peptide synthetases (NRPS) using the conformationally restricted beta-amino acid anthranilate as one of the key building blocks. We validated that the first module of the acetylaszonalenin synthetase of Neosartorya fischeri NRR...
Article
Differentiation-inducing factor 1 (DIF-1) is a polyketide-derived morphogen which drives stalk cell formation in the developmental cycle of Dictyostelium discoideum. Previous experiments demonstrated that the biosynthetic pathway proceeds via dichlorination of the precursor molecule THPH, but the enzyme responsible for this transformation has elude...
Article
Bacillus subtilis produces the antibiotic anticapsin as an L-Ala-L-anticapsin dipeptide precursor known as bacilysin, whose synthesis is encoded by the bacA-D genes and the adjacent ywfGH genes. To evaluate the biosynthesis of the epoxycyclohexanone amino acid anticapsin from the primary metabolite prephenate, we have overproduced, purified, and ch...
Article
Syringolins are a class of cyclic tripeptide natural products that are potent and irreversible inhibitors of the eukaryotic proteasome. In addition to being hybrid NRPS/PKS molecules, they also feature an unusual ureido-linkage (red) between two amino acid monomers. Here we report the first in vitro characterization of enzymatic ureido-linkage form...
Article
The thiocillins are natural-product antibiotics derived from ribosomally encoded peptides that undergo extensive posttranslational modifications to yield the mature trithiazolylpyridine-containing macrocyclic compound. Poor pharmacokinetic properties have prevented the clinical use of these highly potent antibiotics. Through in vivo manipulation of...
Article
The antifungal and antimicrobial kutznerides, hexadepsipeptides composed of one alpha-hydroxy acid and five nonproteinogenic amino acids, are remarkable examples of the structural diversity found in nonribosomally produced natural products. They contain D-3-hydroxyglutamic acid, which is found in the threo and erythro isomers in mature kutznerides....
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Full-text available
We present a time-shared 3D HSQC-NOESY experiment that enables one to simultaneously record (13)C- and (15)N-dispersed spectra in Ile, Leu and Val (ILV) methyl-labeled samples. This experiment is designed to delineate the two spectra which would otherwise overlap with one another when acquired together. These spectra display nOe correlations in the...
Article
Full-text available
The alpha-ketoglutarate-dependent hydroxylases and halogenases employ similar reaction mechanisms involving hydrogen-abstracting Fe(IV)-oxo (ferryl) intermediates. In the halogenases, the carboxylate residue from the His(2)(Asp/Glu)(1) "facial triad" of iron ligands found in the hydroxylases is replaced by alanine, and a halide ion (X(-)) coordinat...
Article
NovP is an S-adenosyl-l-methionine-dependent O-methyltransferase that catalyzes the penultimate step in the biosynthesis of the aminocoumarin antibiotic novobiocin. Specifically, it methylates at 4-OH of the noviose moiety, and the resultant methoxy group is important for the potency of the mature antibiotic: previous crystallographic studies have...
Article
The fungal neurotoxin alpha-cyclopiazonic acid (CPA), a nanomolar inhibitor of Ca(2+)-ATPase with a unique pentacyclic indole tetramic acid scaffold, is assembled by a three enzyme pathway CpaS, CpaD, and CpaO in Aspergillus sp. We recently characterized the first pathway-specific enzyme CpaS, a hybrid two module polyketide synthase-nonribosomal pe...
Article
Full-text available
Nonribosomal peptides have a variety of medicinal activities including activity as antibiotics, antitumor drugs, immunosuppressives, and toxins. Their biosynthesis on multimodular assembly lines as a series of covalently tethered thioesters, in turn covalently attached on pantetheinyl arms on carrier protein way stations, reflects similar chemical...
Article
The fungal neurotoxin alpha-cyclopiazonic acid (CPA), a nanomolar inhibitor of Ca2+-ATPase, has a pentacyclic indole tetramic acid scaffold that arises from one molecule of tryptophan, acetyl-CoA, malonyl-CoA, and dimethylallyl pyrophosphate by consecutive action of three enzymes, CpaS, CpaD, and CpaO. CpaS is a hybrid, two module polyketide syntha...
Article
Full-text available
We present an experiment that allows for a straightforward assignment of NMR resonances, even in large and/or challenging proteins. A single 3D double-TROSY experiment provides three pairs of sequential correlations between two alpha carbons, two amide protons, and two nitrogen nuclei. Thus, all correlated nuclei can readily be visualized within al...
Article
Antibiotic-resistant strains of pathogenic bacteria are increasingly prevalent in hospitals and the community. New antibiotics are needed to combat these bacterial pathogens, but progress in developing them has been slow. Historically, most antibiotics have come from a small set of molecular scaffolds whose functional lifetimes have been extended b...
Article
To acquire iron, the N(2)-fixing, symbiotic bacterium Rhizobium sp. produce the cyclic trihydroxamate siderophore vicibactin, containing a 30-membered trilactone scaffold. Herein we report the overproduction and purification of the six proteins VbsACGOLS in the bacterial host Escherichia coli and the reconstitution of the biosynthesis of vicibactin...
Article
Scientists are using new tools and tactics in the race to discover novel antibiotics
Article
The 39-kDa Escherichia coli enzyme MccB catalyses a remarkable posttranslational modification of the MccA heptapeptide during the biosynthesis of microcin C7 (MccC7), a 'Trojan horse' antibiotic. The approximately 260-residue C-terminal region of MccB is homologous to ubiquitin-like protein (UBL) activating enzyme (E1) adenylation domains. Accordin...
Article
Aliphatic halogenases activate O2, cleave α-ketoglutarate (αKG) to CO2 and succinate, and form haloferryl [X−Fe(IV)O; X = Cl or Br] complexes that cleave aliphatic C−H bonds to install halogens during the biosynthesis of natural products by non-ribosomal peptide synthetases (NRPSs). For the related αKG-dependent dioxygenases, it has been shown that...
Article
CytC3, a member of the recently discovered class of nonheme Fe(II) and R-ketoglutarate (RKG)- dependent halogenases, catalyzes the double chlorination of L-2-aminobutyric acid (Aba) to produce a known Streptomyces antibiotic, gamma,gamma-dichloroaminobutyrate. Unlike the majority of the Fe(II)-RKG-dependentenzymes that catalyze hydroxylation reacti...
Article
Siderophores play a vital role in the survival of bacteria, as they facilitate the transport of iron in low-concentration environments. Nature employs a variety of coordinating functional groups in siderophore scaffolds as a way of creating structural diversity. We have successfully shown that the pseudomonine synthetase can produce three distinct...
Article
With the rise in resistance that inevitably follows the clinical deployment of an antibiotic, there is a continual need for new antibiotic discovery, development and approval. Food and Drug Administration approvals for Synercid (quinupristin/dalfopristin) in 1999, Zyvox (linezolid) in 2000, and Cubicin (daptomycin) in 2003 have addressed life-threa...
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Full-text available
Smoothened (Smo), a 7-pass transmembrane protein, is essential for transduction of a Hedgehog (Hh) signal across the cell membrane. Smo is also the principle therapeutic target for several candidate drugs in the treatment of Hh-related diseases. Mammalian Smo translocates to the primary cilium in response to Sonic hedgehog (Shh) ligand-mediated sig...
Article
The thiazolylpeptides are a family of >50 bactericidal antibiotics that block the initial steps of bacterial protein synthesis. Here, we report a biosynthetic gene cluster for thiocillin and establish that it, and by extension the whole class, is ribosomally synthesized. Remarkably, the C-terminal 14 residues of a 52-residue peptide precursor under...
Article
Full-text available
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-ca...
Article
The conventional notion that peptides are poor candidates for orally available drugs because of protease-sensitive peptide bonds, intrinsic hydrophilicity, and ionic charges contrasts with the diversity of antibiotic natural products with peptide-based frameworks that are synthesized and utilized by Nature. Several of these antibiotics, including p...
Article
Crystals of recombinant NovN, an O-carbamoyltransferase from Streptomyces spheroides, were grown by vapour diffusion. The protein crystallized in two different crystal forms. Crystal form I belonged to space group C2 and native data were collected to 2.9 A resolution in-house. Crystal form II had I-centred orthorhombic symmetry and native data were...
Article
RebC is a putative flavin hydroxylase functioning together with RebP to carry out a key step in the biosynthesis of rebeccamycin. To probe the mechanism of flavin-based chemistry in RebC, we solved the structure of RebC with reduced flavin. Upon flavin reduction, the RebC crystal undergoes a change in its unit cell dimension concurrent with a 5 A m...
Article
Kutznerides are actinomycete-derived antifungal nonribosomal hexadepsipeptides which are assembled from five unsual nonproteinogenic amino acids and one hydroxy acid. Conserved in all structurally characterized kutznerides is a dichlorinated tricyclic hexahydropyrroloindole postulated to be derived from 6,7-dichlorotryptophan. In this Communication...
Article
The pseudomonal phytotoxin syringomycin E and related nonribosomal peptides contain an L- threo-beta-hydroxyaspartyl residue at the eighth position of the lipodepsipeptide backbone as part of a conserved nonproteinogenic tripeptide motif. Informatic analysis of the P. syringae genome suggests only one putative non-heme iron hydroxylase, AspH. On he...
Article
MceIJ is a two protein complex responsible for attachment of a C-glycosylated and linearized derivative of enterobactin, an iron scavenger (siderophore) and product of nonribosomal peptide synthetase machinery, to the C-terminal serine residue of microcin E492 (MccE492), an 84 aa ribosomal antibiotic peptide produced by Klebsiella pneumoniae RYC492...
Article
Polyketide biosynthesis is typically directed by cis-acting catalytic domains. In the case of the Bacillus subtilis secondary metabolite dihydrobacillaene, the cis-acting domains are not sufficient to generate the saturated C14'-C15' bond. In this communication, we identify PksE as a trans-acting enoyl reductase utilized in the biosynthesis of this...
Article
Nitrogen-heteroatom bonds figure prominently in the structural, chemical, and functional diversity of natural products. In the case of Pseudomonas siderophore pseudomonine, an N-O hydroxamate linkage is found uncommonly configured in an isoxazolidinone ring. In an effort to understand the biogenesis of this heterocycle, we have characterized the ps...
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Full-text available
The polyketide signaling metabolites bacillaene and dihydrobacillaene are biosynthesized in Bacillus subtilis on an enzymatic assembly line with both nonribosomal peptide synthetase (NRPS) and polyketide synthase (PKS) modules acting along with catalytic domains servicing the assembly line in trans. These signaling metabolites possess the unusual s...
Article
The antibiotic andrimid, a nanomolar inhibitor of bacterial acetyl coenzyme A carboxylase, is generated on an unusual polyketide/nonribosomal peptide enzyme assembly line in that all thiolation (T) domains/small-molecule building stations are on separate proteins. In addition, a transglutaminase homologue is used to condense andrimid building block...
Article
This review surveys efforts to reconstitute key steps in polyketide and nonribosomal peptide biosynthetic pathways with purified enzymes and substrates; 344 references are cited.
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Full-text available
Non-ribosomal peptide synthetases (NRPS) and polyketide synthases (PKS) found in bacteria, fungi and plants use two different types of thioesterases for the production of highly active biological compounds. Type I thioesterases (TEI) catalyse the release step from the assembly line of the final product where it is transported from one reaction cent...
Article
Full-text available
Andrimid is a hybrid nonribosomal peptide-polyketide antibiotic that blocks the carboxyl-transfer reaction of bacterial acetyl-CoA carboxylase (ACC) and thereby inhibits fatty acid biosynthesis with submicromolar potency. The andrimid biosynthetic gene cluster from Pantoea agglomerans encodes an admT gene with homology to the acetyl-CoA carboxyltra...