title: Repression of the cob operon of Salmonella typhimurium by adenosylcobalamin is influenced by mutations in the pdu operon.
abstract: The cob operon encodes functions needed for the biosynthesis of adenosylcobalamin (Ado-B12). Propanediol induces transcription of the cob operon and the neighboring pdu operon, which encodes proteins for the B12-dependent degradation of propanediol. Expression of the cob (but not the pdu) operon is repressed by exogenous cyanocobalamin. Evidence is provided that cob operon repression is signaled by internally generated Ado-B12, which can be formed either by the CobA adenosyltransferase or by an alternative adenosyltransferase (AdoT) that we infer is encoded within the pdu operon. Repression is also affected by mutations (AdoB) in the pdu operon that map upstream of the inferred pdu adenosyltransferase gene. Such mutations allow cobalamin to mediate repression at concentrations 100-fold lower than those needed in the wild type. It is proposed that these mutations eliminate a component of the propanediol dehydratase enzyme complex (PduCDE) and that this complex competes with the cob regulatory mechanism for a limited supply of Ado-B12.
authors.affiliation: Department of Biology, University of Utah, Salt Lake City, 84112, USA.
authors.forename: M
authors.initials: M
authors.lastname: Ailion
authors.forename: J R
authors.initials: JR
authors.lastname: Roth
mesh_terms: D019883:Alkyl and Aryl Transferases; D001426:Bacterial Proteins; D003038:Cobamides / Q000096:biosynthesis / Q000235:genetics* / Q000494:pharmacology; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D016254:Mutagenesis, Insertional; D009154:Mutation; D009876:Operon; D011401:Promoter Regions, Genetic; D011409:Propylene Glycols / Q000378:metabolism* / Q000494:pharmacology; D012486:Salmonella typhimurium / Q000235:genetics* / Q000378:metabolism; D014166:Transferases / Q000235:genetics*; D014805:Vitamin B 12 / Q000378:metabolism / Q000494:pharmacology
chemical_list: D001426:Bacterial Proteins; D003038:Cobamides; D011409:Propylene Glycols; D014166:Transferases; D019883:Alkyl and Aryl Transferases; C082269:ATP-corrinoid adenosyltransferase; C000913:cobamamide; D014805:Vitamin B 12