title: Thioesterases and the premature termination of polyketide chain elongation in rifamycin B biosynthesis by Amycolatopsis mediterranei S699.
abstract: The role of two thioesterase genes in the premature release of polyketide synthase intermediates during rifamycin biosynthesis in the Amycolatopsis mediterranei S699 strain was investigated. Creation of an in-frame deletion in the rifR gene led to a 30 approximately 60% decrease in the production of both rifamycin B by the S699 strain or a series of tetra- to decaketide shunt products of polyketide chain assembly by the rifF strain. Since a similar percentage decrease was seen in both genetic backgrounds, we conclude that the RifR thioesterase 2 is not involved in premature release of the carbon chain assembly intermediates. Similarly, fusion of the Saccharopolyspora erythraea DEBS3 thioesterase I domain to the C-terminus of the RifE PKS subunit did not result in a noticeable increase in the amount of the undecaketide intermediate formed nor in the amounts of the tetra- to decaketide shunt products. Hence, premature release of the carbon chain assembly intermediates is an unusual property of the Rif PKS itself.
authors.affiliation: School of Pharmacy, University of Wisconsin, Madison 53706, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Doi-Katayama
authors.forename: Y J
authors.initials: YJ
authors.lastname: Yoon
authors.forename: C Y
authors.initials: CY
authors.lastname: Choi
authors.forename: T W
authors.initials: TW
authors.lastname: Yu
authors.forename: H G
authors.initials: HG
authors.lastname: Floss
authors.forename: C R
authors.initials: CR
authors.lastname: Hutchinson
mesh_terms: D000192:Actinomycetales / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000096:biosynthesis*; D001483:Base Sequence; D004950:Esterases / Q000378:metabolism*; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000235:genetics; D009154:Mutation; D010441:Peptide Chain Elongation, Translational; D012294:Rifamycins / Q000096:biosynthesis*
chemical_list: D000900:Anti-Bacterial Agents; D009097:Multienzyme Complexes; D012294:Rifamycins; C033974:rifamycin B; D004950:Esterases