The DeoR-type regulator SugR represses expression of ptsG in Corynebacterium glutamicum

Institute of Biotechnology I, Research Center Juelich, Germany; Institute of Molecular Microbiology and Biotechnology, Westfalian Wilhelms University Muenster, Germany

^* To whom correspondence should be addressed. Email: wendisch{at}uni-muenster.de.

	Abstract

C. glutamicum grows on a variety of carbohydrates and organic acids. Uptake of the preferred carbon source glucose via the phosphoenolpyruvate-dependent phosphotransferase system (PTS) is reduced during co-utilization of glucose with acetate, sucrose or fructose as compared to growth on glucose as sole carbon source. Here we show that the DeoR-type regulator SugR (NCgl1856) represses expression of ptsG, which encodes the glucose-specific PTS enzyme II. Overexpression of sugR resulted in reduced ptsG mRNA levels, diminished expression of a ptsG‘-’cat transcriptional fusion, decreased glucose utilization and perturbed growth on media containing glucose. In mutants lacking sugR, expression of the ptsG‘-’cat fusion was increased two- to sevenfold during growth on gluconeogenic carbon sources, but remained similar during growth on glucose or other sugars. As shown by DNA microarray analysis SugR also regulates expression of other genes including ptsS and the putative NCgl1859-fruK-ptsF operon. Purified SugR bound to DNA regions upstream of ptsG, ptsS and NCgl1859 and a 74 bp ptsG promoter fragment was sufficient for SugR binding. Fructose-6-phosphate interfered with binding of SugR to the ptsG promoter DNA. Thus, while during growth on gluconeogenic carbon sources SugR represses ptsG, ptsG expression is derepressed during growth on glucose or under other conditions characterized by high fructose-6-phosphate concentrations representing one mechanism, which allows C. glutamicum adapting glucose uptake to carbon source availability.