ABSTRACT
The SUC gene family of Saccharomyces includes six structural genes coding for invertase: SUC1—SUC5 and SUC7. The genes of the family are dispersed throughout the yeast genome and have been mapped to the following chromosomes: SUC1, SUC, SUC3, SUC4, SUC5, and SUC7. Closely related strains of S. cerevisiae often differ in SUC gene distribution. Several gene fusions were constructed between the SUC2 gene and the Escherichia coli LacZ gene, which codes for the cytoplasmic enzyme β-galactosidase. Various lengths of SUC2 NH2-terminal coding sequences were fused in frame to a constant segment of the lacZ gene, resulting in the synthesis of hybrid invertase-ß-galactosidase proteins in yeast. Yeast cells harboring the gene fusions did not show extracellular β-galactosidase, even when grown in low glucose. A 2-μm plasmid containing the SUC2 gene and the selectable marker URA3 was mutagenized in vitro with hydroxylamine. This DNA was used to transform a ura3 strain containing a deletion of the SUC2 gene.
