Cloning and sequencing of the GMP synthetase-encoding gene of Saccharomyces cerevisiae

Abstract We have localised, within a Saccharomyces cerevisiae genomic fragment, the GUA 1 gene whose amplification leads to the accumulation of several polypeptides on the two-dimensional (2-D) map of yeast proteins. Comparison of the sequence of the putative GUA1 protein with a data library shows a strong similarity with Escherichia coli , Bacillus subtilis and Dictyostelium discoideum GMP synthetases (GMPS) and other glutamine amidotransferases. The fact that disruption of the chromosomal copy of the gene leads to guanine auxotrophy, that the gual ::URA3 disruption does not complement an independently obtained gual -3 mutation deficient in GMPS and that GUA 1 complements this latter mutation, confirms the identification of the cloned gene as GUA 1 encoding the S. cerevisiae GMPS. Finally, using microsequencing, we have identified one of the polypeptides, which is overproduced in response to GUA 1 amplification, as corresponding to GUA1.