ENZYMES OF THE CYCLIC-GMP METABOLISM IN BOVINE RETINA .1. CLONING AND EXPRESSION OF THE GENE FOR GUANYLATE KINASE

Guanylate kinase (EC 2.7.4.8) catalyzing the reaction GMP + ATP = GDP + ADP, was purified to homogeneity from bovine retina. Using oligonucleotides based on the amino acid sequence of this enzyme, the cDNA encoding guanylate kinase (GK) was isolated and its nucleotide sequence was determined. Expression of the GK cDNA in E. coli, and the purification and functional characterization of the expressed enzyme are presented. It is shown that bovine retinal GK, like its yeast counterpart, contains the characteristic glycine-rich motif and all the amino acids involved in GMP binding. Bovine retinal enzyme is extended for several amino acid residues both at the N- and C-termini, compared to the yeast enzyme.