Evidence that rseC, a gene in the rpoE cluster, has a role in thiamine synthesis in Salmonella typhimurium

In Salmonella typhimurium, the genetic loci and biochemical reactions necessary for the conversion of aminoimidazole ribotide (AIR) to the 4-amino-5-hydroxymethyl-2-methyl pyrimidine (HMP) moiety of thiamine remain unknown. Preliminary genetic analysis indicates that there may be more than one pathway responsible for the synthesis of HMP from ATR and that the function of these pathways depends on the availability of UR, synthesized by the purine pathway or by the purF-independent alternative pyrimidine biosynthetic (APE) pathway (L., Petersen and D. Downs, J., Bacteriol. 178:5676-5682, 1996). An insertion in rseB, the third gene in the rpoE rseABC gene cluster at 57 min, prevented HMP synthesis in a purl: mutant, Complementation analysis demonstrated that the HMP requirement of the purF rseB strain was due to polarity of the insertion in rseB on the downstream rseC gene. The role of RseC in thiamine synthesis was independent of rpoE.