H-072. Regulation of Expression of Genes Encoding General Components of the Phosphoenolpyruvate: Carbohydrate Phosphotransferase System (PTS) in Corynebacterium glutamicum
Background In many bacteria, various sugars are taken up by the phosphoenolpyruvate: carbohydrate phosphotransferase system (PTS). It consists of a sugar-specific transporter and cytoplasmic general components used for any PTS sugar. In Corynebacterium glutamicum, expression of pts genes is enhanced in the presence of PTS sugars. Here, the role of SugR, which was recently reported to regulate expression of the sugar-specific PTS genes, on the expression of the general PTS genes is described. Methods Expression of pts genes was examined by RT-PCR. Histidine-tagged SugR was expressed in Escherichia coli and purified by affinity chromatography. Binding of the SugR to DNA fragments were analyzed by electrophoretic mobility-shift assay (EMSA) and DNase I footprinting. Results Expressions of general PTS genes (ptsI and ptsH) were higher in the sugR disrupted strain than in the C. glutamicum wild-type strain. Introduction of a plasmid containing sugR gene complemented the effect of sugR disruption. Binding of SugR to the promoter region of ptsI and ptsH was indicated by EMSA. DNase I footprinting analysis indicated the binding site of SugR on the promoter region of ptsI. The binding site has repeats of TG(T)2-5G sequences which is present in all the promoter regions of pts genes. The binding site also contains the GTTGCACA sequence which was reported to be the putative SugR binding sequence for the promoter region of glucose-specific pts gene. Mutations at these motifs resulted in the decrease of SugR binding to the ptsI promoter. Conclusion These results suggest that SugR acts as a repressor of general PTS genes, in addition to the sugar specific PTS genes. We also determined a new SugR binding motif TG(T)2-5G which is conserved in the promoter regions of general and sugar-specific PTS genes. Acknowledgement This work was partially supported by a grant from the New Energy and Industrial Technology Development Organization (NEDO). Key words Corynebacterium glutamicum, PTS, sugR