title: Insertional inactivation of methylmalonyl coenzyme A (CoA) mutase and isobutyryl-CoA mutase genes in Streptomyces cinnamonensis: influence on polyketide antibiotic biosynthesis.
abstract: The coenzyme B(12)-dependent isobutyryl coenzyme A (CoA) mutase (ICM) and methylmalonyl-CoA mutase (MCM) catalyze the isomerization of n-butyryl-CoA to isobutyryl-CoA and of methylmalonyl-CoA to succinyl-CoA, respectively. The influence that both mutases have on the conversion of n- and isobutyryl-CoA to methylmalonyl-CoA and the use of the latter in polyketide biosynthesis have been investigated with the polyether antibiotic (monensin) producer Streptomyces cinnamonensis. Mutants prepared by inserting a hygromycin resistance gene (hygB) into either icmA or mutB, encoding the large subunits of ICM and MCM, respectively, have been characterized. The icmA::hygB mutant was unable to grow on valine or isobutyrate as the sole carbon source but grew normally on butyrate, indicating a key role for ICM in valine and isobutyrate metabolism in minimal medium. The mutB::hygB mutant was unable to grow on propionate and grew only weakly on butyrate and isobutyrate as sole carbon sources. (13)C-labeling experiments show that in both mutants butyrate and acetoacetate may be incorporated into the propionate units in monensin A without cleavage to acetate units. Hence, n-butyryl-CoA may be converted into methylmalonyl-CoA through a carbon skeleton rearrangement for which neither ICM nor MCM alone is essential.
authors.affiliation: Department of Chemistry, University of Zurich, CH-8057 Zurich, Switzerland.
authors.forename: J W
authors.initials: JW
authors.lastname: Vrijbloed
authors.forename: K
authors.initials: K
authors.lastname: Zerbe-Burkhardt
authors.forename: A
authors.initials: A
authors.lastname: Ratnatilleke
authors.forename: A
authors.initials: A
authors.lastname: Grubelnik-Leiser
authors.forename: J A
authors.initials: JA
authors.lastname: Robinson
mesh_terms: D001426:Bacterial Proteins; D002247:Carbon Isotopes; D004352:Drug Resistance, Microbial / Q000235:genetics; D007535:Isomerases / Q000235:genetics* / Q000378:metabolism*; D046911:Macromolecular Substances; D008765:Methylmalonyl-CoA Mutase / Q000235:genetics* / Q000378:metabolism*; D008985:Monensin / Q000096:biosynthesis / Q000737:chemistry; D016254:Mutagenesis, Insertional; D010641:Phenotype; D013302:Streptomyces / Q000201:enzymology* / Q000235:genetics* / Q000254:growth & development
chemical_list: D001426:Bacterial Proteins; D002247:Carbon Isotopes; D046911:Macromolecular Substances; D008985:Monensin; D007535:Isomerases; C107545:isobutyryl-CoA mutase, Streptomyces; D008765:Methylmalonyl-CoA Mutase