title: Methylbenzene-Containing Polyketides from a Streptomyces that Spontaneously Acquired Rifampicin Resistance: Structural Elucidation and Biosynthesis.
abstract: Conventional screening for novel bioactive compounds in actinomycetes often results in the rediscovery of known compounds. In contrast, recent genome sequencing revealed that most of the predicted gene clusters for secondary metabolisms are not expressed under standard cultivation conditions. To explore the potential metabolites produced by these gene clusters, we implemented a cryptic gene activation strategy by screening mutants that acquire resistance to rifampicin. The induction of rifampicin resistance in 11 actinomycete strains generated 164 rifampicin-resistant mutants (rif mutants). The comparison of the metabolic profiles between the rif mutants and their wild-type strains indicated that one mutant (TW-R50-13) overproduced an unidentified metabolite (1). During the isolation and structural elucidation of metabolite 1, an additional metabolite was found; both are unprecedented compounds featuring a C5N unit and a methylbenzene moiety. Of these partial structures, the biosynthesis of the latter has not been reported. A feeding experiment using (13)C-labeled precursors demonstrated that the methylbenzene moiety is most likely synthesized by the action of polyketide synthase. The gene deletion experiments revealed that the genes for the methylbenzene moiety are located at a different locus than the genes for the C5N unit.
authors.affiliation: Biotechnology Research Center, The University of Tokyo , 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
authors.forename: Wei Li
authors.initials: WL
authors.lastname: Thong
authors.affiliation: National Institute of Advanced Industrial Science and Technology (AIST) , 2-4-7 Aomi, Koto-ku, Tokyo 135-0064, Japan.
authors.forename: Kazuo
authors.initials: K
authors.lastname: Shin-ya
authors.affiliation: Biotechnology Research Center, The University of Tokyo , 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Nishiyama
authors.affiliation: Biotechnology Research Center, The University of Tokyo , 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
authors.forename: Tomohisa
authors.initials: T
authors.lastname: Kuzuyama
mesh_terms: D039903:Actinobacteria / Q000737:chemistry* / Q000235:genetics; D008826:Microbial Sensitivity Tests; D015394:Molecular Structure; D005810:Multigene Family; D019906:Nuclear Magnetic Resonance, Biomolecular; D048630:Polyketide Synthases / Q000378:metabolism; D061065:Polyketides / Q000737:chemistry* / Q000302:isolation & purification*; D012293:Rifampin / Q000737:chemistry / Q000494:pharmacology*; D013302:Streptomyces / Q000737:chemistry / Q000235:genetics*
chemical_list: D061065:Polyketides; D048630:Polyketide Synthases; D012293:Rifampin