Jim Staunton

University of Cambridge, Cambridge, ENG, United Kingdom

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Publications (3)10.58 Total impact

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    ABSTRACT: A previously unidentified set of genes encoding a modular polyketide synthase (PKS) has been sequenced in Saccharopolyspora erythraea, producer of the antibiotic erythromycin. This new PKS gene cluster (pke) contains four adjacent large open reading frames (ORFs) encoding eight extension modules, flanked by a number of other ORFs which can be plausibly assigned roles in polyketide biosynthesis. Disruption of the pke PKS genes gave S. erythraea mutant JC2::pSBKS6, whose growth characteristics and pattern of secondary metabolite production did not apparently differ from the parent strain under any of the growth conditions tested. However, the pke PKS loading module and individual pke acyltransferase domains were shown to be active when used in engineered hybrid PKSs, making it highly likely that under appropriate conditions these biosynthetic genes are indeed expressed and active, and synthesize a novel polyketide product.
    Journal of Molecular Microbiology and Biotechnology 02/2004; 8(2):73-80. DOI:10.1159/000084562 · 1.49 Impact Factor
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    ABSTRACT: Sequence comparisons of multiple acyltransferase (AT) domains from modular polyketide synthases (PKSs) have highlighted a correlation between a short sequence motif and the nature of the extender unit selected. When this motif was specifically altered in the bimodular model PKS DEBS1-TE of Saccharopolyspora erythraea, the products included triketide lactones in which acetate extension units had been incorporated instead of propionate units at the predicted positions. We also describe a cassette system for convenient construction of hybrid modular PKSs based on the tylosin PKS in Streptomyces fradiae and demonstrate its use in domain and module swaps.
    Journal of Industrial Microbiology and Biotechnology 09/2003; 30(8):489-94. DOI:10.1007/s10295-003-0062-0 · 2.51 Impact Factor
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    ABSTRACT: Polyketides are a large and structurally diverse group of natural products that include antibiotics, antifungal agents and immunosuppressant compounds. Polyketides are biosynthesised in filamentous bacteria on modular polyketide synthases (PKSs) in which each cycle of chain extension requires a different 'module' of enzymatic activities. The recently proposed dimeric model for modular PKSs predicts that even a single-module PKS should be catalytically active in the absence of other PKS components. Researchers are also interested in manipulating the stereochemical outcome of polyketide chain extension using genetic engineering of domains within each module. We have constructed a minimal modular PKS from the erythromycin-producing PKS (DEBS) of Saccharopolyspora erythraea. The diketide synthase (DKS1-2) consists of a single chimaeric extension module, derived from the DEBS module 1 ketoacyl-ACP synthase (KS), sandwiched between a loading module and a chain-terminating thioesterase. When DKS1-2 was expressed in S. erythraea, the strain preferentially6 accumulated the diketide (2R, 3S)-2-methyl-3-hydroxy pentanoic acid. These results demonstrate that, as predicted, even a single-module PKS is catalytically active in the absence of other DEBS proteins. In its normal context, the ketosynthase domain KS1 is thought to generate a (2S)-2methyl-3-hydroxy intermediate by epimerising the initial product of carbon-carbon chain formation, the (2R)-2-methyl-3-ketoester. The observed formation of the alternative (2R)-methyl-3-hydroxy product catalysed by DKS1-2 provides strong support for this proposal, and indicates how targeted alteration of stereospecificity can be achieved on a modular PKS.
    Chemistry & Biology 09/1998; 5(8):407-12. DOI:10.1016/S1074-5521(98)90157-0 · 6.59 Impact Factor