Cloning and expression of the essential gene for guanylate kinase from yeast

Guanylate kinase catalyzes the reversible transfer of the terminal phosphoryl group of ATP to the acceptor molecule GMP. Detailed analysis of the in vivo function of this enzyme has been limited by the lack of any genetic data. Using oligonucleotides based on amino acid sequence information of the yeast enzyme, the Saccharomyces cerevisiae gene, GUK1, was isolated and characterized. The gene is present in single copy and maps to chromosome IV. Insertional mutagenesis of the GUK1 locus caused recessive lethality, indicating that this enzyme is necessary for vegetative cell growth. Using inducible expression systems, guanylate kinase was produced in large amounts both in S. cerevisiae and in Escherichia coli.