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Journal of Bacteriology, June 2004, p. 3453-3460, Vol. 186, No. 11
0021-9193/04/$08.00+0     DOI: 10.1128/JB.186.11.3453-3460.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

Identification and Characterization of glxR, a Gene Involved in Regulation of Glyoxylate Bypass in Corynebacterium glutamicum

Hyung-Joon Kim,1 Tae-Hyun Kim,1 Younhee Kim,2 and Heung-Shick Lee1,3*

Graduate School of Biotechnology, Korea University, Anam-Dong, Sungbuk-Ku, Seoul 136-701,1 Department of Oriental Medicine, Semyung University, Checheon, Chungbuk 390-230,2 Department of Biotechnology, Korea University, Jochiwon, Choongnam 339-700, Korea3

Received 3 September 2003/ Accepted 11 February 2004

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.


* Corresponding author. Mailing address: Graduate School of Biotechnology, Korea University, Anam-Dong, Sungbuk-Ku, Seoul 136-701, Korea. Phone: 82-41-860-1415. Fax: 82-41-864-2665. E-mail: hlee{at}korea.ac.kr.


Journal of Bacteriology, June 2004, p. 3453-3460, Vol. 186, No. 11
0021-9193/04/$08.00+0     DOI: 10.1128/JB.186.11.3453-3460.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.




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