Nucleotide sequence of the purM gene encoding 5'-phosphoribosyl-5-aminoimidazole synthetase of Escherichia coli K12.

5'-Phosphoribosyl-5-aminoimidazole synthetase (EC 6.3.3.1), encoded by the purM gene of Escherichia coli, catalyzes the synthesis of 5'-phosphoribosyl-5-aminoimidazole from 5'-phosphoribosylformylglycinamidine. The purM gene was subcloned from the Clarke and Carbon (Clarke, L., and Carbon, J. (1976) Cell 9, 91-99) plasmid pLC1-41 and the nucleotide sequence determined. The mature protein, as deduced from the purM structural gene sequence, contains 344 amino acid residues and has a calculated Mr of 36,726. The 5' end of the purM mRNA was determined by mung bean nuclease mapping to be 44-45 nucleotides up-stream of the proposed GTG translation initiation codon. A C-G-rich region characteristic of stringently controlled promoters is located immediately in front of the proposed purM promoter region. Comparison of the upstream sequences of the purM and the coregulated purF loci revealed a highly conserved (33 of 39 base pairs are identical) sequence. The presumptive purM promoter is located in this region, thus suggesting that both purine loci share a common mechanism of regulation mediated through this sequence.