Organization and Analysis of the Histidine Biosynthetic Genes from Corynebacterium Glutamicum

Abstract

Corynebacterium glutamicum, a Gram-positive bacterium, has been widely used for industrial amino acid production. In addition to our previously cloned hisEG and hisHA-impA-hisFI genes, the remaining hisDCB genes were cloned in this study. The entire C glutamicum histidine biosynthesis genes, when compared with those of other microorganisms, showed high degree of similarities in deduced amino acid sequences but also significant differences in gene organization. Transcription analysis by RT-PCR revealed that C glutamicum his genes are located and transcribed in two unlinked loci, hisEG and hisDCB-orf1-orf2-hisHA-impA-impA-hisFI. The primer extension analysis showed that the latter his operon starts the transcription at C residue localized 196-bp upstream of the hisD ATG start codon. Genetic analysis in hisD promoter region showed the putative Pribnow boxes, TTTAAT and CAGTAT at 7 and 31 upstream of hisD gene transcription start site. Further analysis revealed Shine-Dalgarno sequence, AGGGAG, at 10-bp upstream of hisD translational start codon. Our result also suggests that the histidine biosynthesis in C glutamicum is negatively regulated by their end-product, histidine, suggesting the histidine-dependent regulation of his gene transcription.