Regulation of expression of general components of the phosphoenolpyruvate:: carbohydrate phosphotransferase system (PTS) by the global regulator SugR in Corynebacterium glutamicum

The phosphoenolpyruvate: carbohydrate phosphotransferase system (PTS) catalyzes transport of carbohydrates by coupling carbohydrate translocation and phosphorylation. Enzyme I and HPr, encoded in ptsI and ptsH, respectively, are cytoplasmic proteins commonly used for transport of variety of PTS sugars. In this study, we investigated the role of SugR on the expression of the ptsI and ptsH which increases in the presence of PTS sugars in Corynebacterium glutamicum. Disruption of sugR resulted in the increased expression of ptsI and ptsH in the absence of PTS sugar. Introduction of a plasmid containing sugR gene complemented the effect of sugR disruption. SugR was purified and binding to the promoter regions of ptsI and ptsH was indicated by EMSA. DNase I footprinting analysis indicated the binding sites of SugR on the promoter region of divergently transcribed ptsI gene and fructose-pts operon. The binding sites contain a possible SugR binding motif which is conserved in the promoter regions of general and sugar-specific pts genes. Mutations in this motif resulted in the decrease of SugR binding to the ptsI promoter. These results suggest that SugR represses ptsI and ptsH in the absence of PTS sugar and derepression is the mechanism for the induction of the general components of PTS.