[Guanylate kinase from bovine retina: isolation, primary structure, and expression in E. coli]

Guanylate kinase (EC 2.7.4.8), catalysing the reaction GMP+ATP = GDP+ADP, was purified to homogeneity from bovine retina. Primary structure of the enzyme was determined by parallel analyses of amino acid sequences of its peptides and nucleotide sequence of the corresponding cDNA. It is shown that the bovine retinal guanylate kinase like the analogous enzyme from yeast Saccharomyces cerevisiae contains a characteristic glycine-rich motif, involved in ATP binding. All of the amino acids, involved in GMP binding in the yeast enzyme, are conserved or conservatively substituted in the bovine retinal guanylate kinase. The bovine retinal enzyme was expressed in E. coli as a fusion protein. Data are presented on the purification of the fusion protein, its digestion by enteropeptidase, purification of the recombinant enzyme and its functional characteristics.