Cloning and sequencing of the adenylate kinase gene (adk) ofEscherichia coli

Adenylate kinase, the product of the adk locus in Escherichia coli K12, catalyzes the conversion of AMP and ATP to two molecules of ADP. The gene has been cloned by complementation of an adk temperature sensitive mutation. The DNA sequence of the complete coding region and of 5'- and 3'-untranslated regions were determined. The resulting protein sequence was found to contain several regions of high homology with cytosolic adenylate kinase of pig muscle (AK1), whose three-dimensional structure has been determined. The most significant of the amino acid exchanges is the replacement of histidine 36 with glutamine. This residue is believed to play a role in catalysis through metal ion binding. The codon usage pattern and the determination of adenylate kinase molecules per cell shows that the enzyme is one of the more abundant soluble proteins of the bacterial cells.