title: cobB function is required for catabolism of propionate in Salmonella typhimurium LT2: evidence for existence of a substitute function for CobB within the 1,2-propanediol utilization (pdu) operon.
abstract: The cobB function of Salmonella typhimurium LT2 was defined in vivo as an alternative activity for the nicotinic acid mononucleotide:5,6-dimethylbenzimidazole phosphoribosyltransferase enzyme (CobT), which is involved in the assembly of the nucleotide loop of cobalamin in this bacterium (J. R. Trzebiatowski, G. A. O'Toole, and J. C. Escalante-Semerena, J. Bacteriol. 176:3568-3575, 1994). In this paper we document that, independent of their inability to substitute for CobT function, cobB mutants are unable to use propionate as a carbon and energy source. A plasmid carrying only a wild-type copy of cobB complemented the cobalamin biosynthesis and propionate catabolism phenotypes of cobB mutants, indicating that a lack of CobB was responsible for both phenotypes. We demonstrate the existence of a function encoded by the 1,2-propanediol utilization (pdu) operon, which when induced by 1,2-propanediol compensated for the lack of CobB during propionate catabolism but failed to compensate for CobT in the assembly of the nucleotide loop of cobalamin in a cobB cobT double mutant.
authors.affiliation: Department of Bacteriology, University of Wisconsin-Madison, 53706-1567, USA.
authors.forename: A W
authors.initials: AW
authors.lastname: Tsang
authors.forename: J C
authors.initials: JC
authors.lastname: Escalante-Semerena
mesh_terms: D005798:Genes, Bacterial; D009154:Mutation; D009876:Operon; D011422:Propionates / Q000378:metabolism*; D019946:Propylene Glycol; D011409:Propylene Glycols / Q000378:metabolism*; D012486:Salmonella typhimurium / Q000235:genetics* / Q000378:metabolism; D014805:Vitamin B 12 / Q000096:biosynthesis
chemical_list: D011422:Propionates; D011409:Propylene Glycols; D019946:Propylene Glycol; D014805:Vitamin B 12