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J. Bacteriol., Dec 1996, 7016-7019, Vol 178, No. 23
AW Tsang and JC Escalante-Semerena
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.
Copyright © 1996, American Society for Microbiology
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
Department of Bacteriology, University of Wisconsin-Madison, 53706- 1567, USA.
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