Nucleotide sequence and analysis of the purA gene encoding adenylosuccinate synthetase of Escherichia coli K12.

Adenylosuccinate synthetase (EC 6.3.4.4), encoded by the purA gene of Escherichia coli K12, catalyzes the synthesis of adenylosuccinate (SAMP) from IMP, the first committed step in AMP biosynthesis. The E. coli K12 purA gene and flanking DNA was cloned by miniMu-mediated transduction, and the nucleotide sequence was determined. The mature SAMP synthetase subunit, as deduced from the DNA sequence, contains 427 amino acid residues and has a calculated Mr of 47,277. The size of the purA mRNA was determined by Northern blotting to be approximately 1.5 kilobase pairs. The 5'-end of the purA mRNA was identified by primer extension and is located 23 nucleotides upstream of the ATG translational initiation codon. Comparison of the purA control region with the guaBA control region revealed a common region of dyad symmetry which may suggest mutual elements of regulation. The purA control region did not resemble the control regions of the other known pur loci.