Identification and characterization of glxR, a gene involved in regulation of glyoxylate bypass in Corynebacterium glutamicum.
A corynebacterial clone, previously isolated by scoring repression of lacZYA fused to the aceB promoter of Corynebacterium glutamicum, was analyzed further. In the clone, an open reading frame designated glxR, consisting of 681 nucleotides and encoding a 24,957-Da protein, was found. The molecular mass of a native GlxR protein was estimated by gel filtration column chromatography to be 44,000 Da, suggesting that the protein formed dimers. The predicted amino acid sequence contained both cyclic AMP (cAMP)- and DNA-binding motifs and was homologous with the cAMP receptor protein family of proteins. The aceB-repressing activity of the glxR clone was markedly relieved in an Escherichia coli cya mutant, but the activity was restored in growth medium containing cAMP. In glucose medium, the intracellular cAMP concentration of C. glutamicum reached 22 nmol/mg of protein in the early exponential phase and then decreased further; but in acetate medium, the intracellular cAMP concentration was only 5 nmol/mg of protein and remained low throughout the growth phase. The expression of glxR was not affected by the carbon source. Binding of purified GlxR to the promoter region of aceB could be demonstrated only in the presence of cAMP. These data suggest that GlxR may form dimers which bind to the aceB promoter region in the presence of cAMP and repress the glyoxylate bypass genes.
Kim
Hyung-Joon
HJ
Graduate School of Biotechnology, Korea University, Anam-Dong, Sungbuk-Ku, Seoul 136-701, Korea.
Kim
Tae-Hyun
TH
Kim
Younhee
Y
Lee
Heung-Shick
HS
D000595:Amino Acid Sequence; D003352:Corynebacterium / Q000235:genetics*; D000242:Cyclic AMP / Q000502:physiology; D004269:DNA, Bacterial / Q000378:metabolism; D019281:Dimerization; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial / Q000502:physiology*; D006038:Glyoxylates / Q000378:metabolism*; D008292:Malate Synthase / Q000235:genetics; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic
D004269:DNA, Bacterial; D006038:Glyoxylates; D000242:Cyclic AMP; D008292:Malate Synthase; C031150:glyoxylic acid