Analysis of gene expression in arginine biosynthetic gene cluster of Corynebacterium glutamicum

Abstract

Corynebacterium glutamicum, a Gram-positive bacterium, has been widely used for industrial amino acid production. We have cloned and analyzed arginine gene cluster in this organism. Although, many other bacteria have ArgA (N-acetylglutamate synthase, NAGS), the gene is not found in chromosomal DNA of C glutamicum. Interestingly, significant identity was found between C glutamicum ArgB and N-terminal domain of E coli ArgA in a comparison of amino acid sequences. Moreover, C glutamicum argB gene encoding N-acetylglutamate kinase (NAGK) was able to complement K coli argA auxotroph as well as argB mutant, suggesting C. glutamicum ArgB is a bifunctional enzyme with both NAGS and NAGK activities. The analysis of Northern hybridization and RT-PCR showed that the arginine biosynthesis gene cluster synthesizes two transcripts corresponding to argCJBDFR and agrGH in C glutamicum. The respective transcriptions were started at A and T residues which are located 30bp or 44bp upstream from translation start codon for argC and argG genes respectively. The promoter regions were also analyzed in the region preceding the respective transcription initiate sites. Interestingly, we found that arginine, end product of arginine biosynthesis pathway, regulates the gene expression of argCJBDFR but not argGH.