Expression and secretion of foreign proteins in yeast using the ADH1 promoter and 97 K killer toxin signal sequence

Foreign proteins, endo-beta-1,4-glucanase of Bacillus subtilis, preS1+S2 region of hepatitis B virus large surface antigen, human beta(2)-adrenergic receptor (h beta(2)AR), and bovine growth hormone (bGH) were expressed in Saccharomyces cerevisiae and secreted into the medium. These proteins were expressed using the alcohol dehydrogenase I (ADH1) promoter of Saccharomyces cerevisiae and secreted by signal sequence of the 97 K killer toxin gene of double-stranded linear DNA plasmid (pGKL1) of S. cerevisiae, All these proteins underwent severe modifications; in particular, N-glycosylation in the case of endo-beta-1,4-glucanase, h beta(2)AR, and preS1+S2. Seventy four percent of the expressed endo-beta-1,4-glucanase was secreted into the culture medium. Highly modified proteins were detected in the culture medium and in the cell. Expressed h beta(2)AR, which has seven transmembrane domains, remained in the cell. The degrees of secretion and modification and the states of proteins in the culture medium and in the cell were quite different. These results indicated that the nature of the protein has a critical role in its secretion and modifications.