A common regulator for the operons encoding the enzymes involved in D-galactarate, D-glucarate, and D-glycerate utilization in Escherichia coli

Genes for D-galactarate (gar) and D-glucarate (gud) metabolism in Escherich ia coli are organized in three transcriptional units: garD, garPLRK, and gu dPD. Two observations suggested a common regulator for the three operons. ( i) Their expression was triggered by D-galactarate, D-glucarate, and D-glyc erate. (ii) Metabolism of the three compounds was impaired by a single Tn5 insertion mapped in the yaeG gene (proposed name, sdaR), outside the D-gala ctarate and D-glucarate systems. Expression of the sdaR gene is autogenousl y regulated.