title: Structure elucidation of new ascomycins produced by genetic engineering.
abstract: Three new ascomycins produced by genetic engineering of Streptomyces hygroscopicus ATCC 14891 have been purified and characterized. Replacement of the 13-methoxyl group of ascomycin was accomplished by substitution of the corresponding acyltransferase domain of the polyketide synthase with a domain specific for either malonyl-CoA or methylmalonyl-CoA. The strain containing the methylmalonyl-specific acyltransferase domain produced a compound with properties consistent with those expected for 13-demethoxy-13-methylascomycin. NMR analysis revealed this material to be predominantly the cis amide rotamer, similar to ascomycin. The strain containing the malonyl-specific acyltransferase domain produced a mixture of two compounds, 13-demethoxyascomycin and the 9,14-hemiacetal isomer of 13-demethoxyascomycin, in nearly equal amounts. NMR analysis revealed both compounds to be predominantly the trans amide rotamers.
authors.affiliation: Department of Chemistry and Process Science, Kosan Biosciences, Inc., 3832 Bay Center Place, Hayward, CA 94545, USA. carney@kosan.com
authors.forename: John R
authors.initials: JR
authors.lastname: Carney
authors.forename: Gary W
authors.initials: GW
authors.lastname: Ashley
authors.forename: Robert L
authors.initials: RL
authors.lastname: Arslanian
authors.forename: Greg O
authors.initials: GO
authors.lastname: Buchannan
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D005818:Genetic Engineering; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D048630:Polyketide Synthases / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D013237:Stereoisomerism; D013302:Streptomyces / Q000235:genetics* / Q000378:metabolism; D016559:Tacrolimus / Q000031:analogs & derivatives* / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D048630:Polyketide Synthases; C058028:immunomycin; D016559:Tacrolimus