Corynebacterium glutamicum is a Gram-positive soil bacterium that is widely used for the industrial production of amino acids, e.g., L-glutamate and L-lysine. We have investigated C. glutamicum R for production of organic acids and ethanol under oxygen-deprived conditions. The glycolytic pathway presents an important target to manipulate in order to improve the production yields, even though inadequate information on transcriptional regulation of glycolytic genes is currently available. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH), which catalyzes oxidative phosphorylation of glyceraldehyde-3-phosphate, is a key enzyme in glycolysis. In this study, we investigated transcriptional regulation of the gapA gene encoding GAPDH essential for glycolysis in C. glutamicum R. We applied DNA affinity beads to isolate proteins binding to the promoter region of the gapA gene and obtained SugR, which has been shown to be a repressor of pts genes involved in sugar transport system. Electrophoretic mobility shift assays revealed that SugR specifically bound to the gapA promoter. We examined expression of the gapA gene in a sugR deletion mutant. Effects of mutation in the SugR binding site on gapA-lacZ fusion expression were also examined. These assays revealed that SugR acts as a negative transcriptional regulator of the gapA gene in the absence of sugar, and repression by SugR is alleviated in the presence of sugar, i.e., fructose and sucrose.

This work was partially supported by a grant from the New Energy and Industrial Technology Development Organization (NEDO).