Regulation of purine biosynthetic genes expression in Salmonella typhimurium Ⅳ O^c mutation site of purG and its function analysis

Salmonella typhimurium 5 phosphoribosylformylglycinamide (FGAR) amidotransferase encoded by purG gene catalyzes the conversion of FGAR to formylglycinamide ribonucleotide (FGAM) in the presence of glu-tamine and ATP for the de novo purine nucleotide biosynthesis. purG gene is negatively regulated by a repressor-oper-ator system. The O+ purG and OC purG were cloned respectively in vivo. Restriction enzymes analysis of preliminary clones pLBG-1 (O + ) and pLBG-2 (OC) were carried out. The hybrid plasmids pLB1933 (O+ ) and pLB1927 (OC) containing 5 control region of purG were constructed and the DNA sequences were determined respectively. DNA se-quences data showed that Oc mutation of purG occurred at the 3rd position of 16 bp PUR box in the 5' control region ( G→A). Gel retardation experiment indicated that the repressor bound well with O+ PUR box, but not with Oc PUR box. The result strongly supported the idea that PUR box is the binding region of represser protein and the 3rd posi-tion base G of PUR box is essential for the binding function with repressor protein.

Salmonella typhimurium 5 phosphoribosylformylglycinamide (FGAR) amidotransferase encoded by purG gene catalyzes the conversion of FGAR to formylglycinamide ribonucleotide (FGAM) in the presence of glu-tamine and ATP for the de novo purine nucleotide biosynthesis. purG gene is negatively regulated by a repressor-oper-ator system. The O+ purG and OC purG were cloned respectively in vivo. Restriction enzymes analysis of preliminary clones pLBG-1 (O + ) and pLBG-2 (OC) were carried out. The hybrid plasmids pLB1933 (O+ ) and pLB1927 (OC) containing 5 control region of purG were constructed and the DNA sequences were determined respectively. DNA se-quences data showed that Oc mutation of purG occurred at the 3rd position of 16 bp PUR box in the 5’ control region ( G→A). Gel retardation experiment indicated that the repressor bound well with O+ PUR box, but not with Oc PUR box. The result strongly supported the idea that PUR box is the binding region of represser protein and the 3rd posi-tion base G of PUR