title: Cloning of the pactamycin biosynthetic gene cluster and characterization of a crucial glycosyltransferase prior to a unique cyclopentane ring formation.
abstract: The biosynthetic gene (pct) cluster for an antitumor antibiotic pactamycin was identified by use of a gene for putative radical S-adenosylmethionine methyltransferase as a probe. The pct gene cluster is localized to a 34 kb contiguous DNA from Streptomyces pactum NBRC 13433 and contains 24 open reading frames. Based on the bioinformatic analysis, a plausible biosynthetic pathway for pactamycin comprising of a unique cyclopentane ring, 3-aminoacetophenone, and 6-methylsalicylate was proposed. The pctL gene encoding a glycosyltransferase was speculated to be involved in an N-glycoside formation between 3-aminoacetophenone and UDP-N-acetyl-alpha-D-glucosamine prior to a unique cyclopentane ring formation. The pctL gene was then heterologously expressed in Escherichia coli and the enzymatic activity of the recombinant PctL protein was investigated. Consequently, the PctL protein was found to catalyze the expected reaction forming beta-N-glycoside. The enzymatic activity of the PctL protein clearly confirmed that the present identified gene cluster is for the biosynthesis of pactamycin. Also, a glycosylation prior to cyclopentane ring formation was proposed to be a general strategy in the biosynthesis of the structurally related cyclopentane containing compounds.
authors.affiliation: Department of Chemistry, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8551, Japan. fkudo@chem.titech.ac.jp
authors.forename: Fumitaka
authors.initials: F
authors.lastname: Kudo
authors.forename: Yuko
authors.initials: Y
authors.lastname: Kasama
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Hirayama
authors.forename: Tadashi
authors.initials: T
authors.lastname: Eguchi
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D003517:Cyclopentanes / Q000737:chemistry / Q000378:metabolism*; D005798:Genes, Bacterial / Q000235:genetics*; D005960:Glucosides / Q000378:metabolism; D006031:Glycosylation; D016695:Glycosyltransferases / Q000235:genetics* / Q000378:metabolism*; D005810:Multigene Family; D016366:Open Reading Frames / Q000502:physiology; D010142:Pactamycin / Q000096:biosynthesis* / Q000737:chemistry; D012459:Salicylates / Q000378:metabolism; D013302:Streptomyces / Q000235:genetics* / Q000378:metabolism