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Gene Review:

cobB - NAD-dependent deacetylase

Salmonella enterica subsp. enterica serovar Typhimurium str. LT2

Tsang, A.W. et al., Tsang, A.W. et al., Tsang, A.W. et al., Chen, P. et al.

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Disease relevance of cobB

The cobB gene of Salmonella typhimurium LT2 has been isolated and genetically and biochemically characterized. cobB was located by genetic means to the 27-centisome region of the chromosome [1].

High impact information on cobB

Genetic crosses established the gene order to be cobB pepT phoQ, and the direction of cobB transcription was shown to be clockwise [1].
Possible roles of CobB as a regulator are discussed within the context of the catabolism of propionate, a pathway known to require cobB function (Tsang, A. W. and Escalante-Semerena, J. C. (1996) J. Bacteriol. 178, 7016-7019) [1].
The nucleotide sequence of cobB (711 base pairs) predicted a protein of 237 amino acids length with a molecular mass of 26.3 kDa, a mass consistent with the experimentally determined one of approximately 28 kDa [1].
DNA sequence analysis of the region flanking cobB located it 81 base pairs 3' of the potABCD operon, with the potABCD operon and cobB being divergently transcribed. cobB was overexpressed to approximately 30% of the total soluble protein using a T7 overexpression system [1].
The cobB gene was defined genetically by deletions (10), insertions (5), and point mutations (15) [1].

Chemical compound and disease context of cobB

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 [2].

Biological context of cobB

Since synthesis of this Pdu protein depends on the availability of 1,2-propanediol, the cell solves the problem faced in an environment devoid of 1,2-propanediol where propionate is the sole carbon and energy source by having cobB located outside of the pdu operon and its expression independent of 1,2-propanediol [3].
Some cobT mutants appear defective only in DMB synthesis, since they grow on low levels of DMB and retain their CobII phenotype in the presence of a cobB mutation [4].
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 [2].

Associations of cobB with chemical compounds

Expression of the prpBCDE operon in cobB mutants was restored to wild-type levels upon induction of the propanediol utilization (pdu) operon by 1,2-propanediol [3].

References

CobB, a new member of the SIR2 family of eucaryotic regulatory proteins, is required to compensate for the lack of nicotinate mononucleotide:5,6-dimethylbenzimidazole phosphoribosyltransferase activity in cobT mutants during cobalamin biosynthesis in Salmonella typhimurium LT2. Tsang, A.W., Escalante-Semerena, J.C. J. Biol. Chem. (1998) [Pubmed]
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. Tsang, A.W., Escalante-Semerena, J.C. J. Bacteriol. (1996) [Pubmed]
Studies of regulation of expression of the propionate (prpBCDE) operon provide insights into how Salmonella typhimurium LT2 integrates its 1,2-propanediol and propionate catabolic pathways. Tsang, A.W., Horswill, A.R., Escalante-Semerena, J.C. J. Bacteriol. (1998) [Pubmed]
The end of the cob operon: evidence that the last gene (cobT) catalyzes synthesis of the lower ligand of vitamin B12, dimethylbenzimidazole. Chen, P., Ailion, M., Weyand, N., Roth, J. J. Bacteriol. (1995) [Pubmed]

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