Yeast as an expression system for the production of bacterial and viral antigens.

To develop a yeast system that expresses bacterial and viral antigens in the future, we analyzed yeast secretion with a reporter system based on the cc1A gene of Clostridium thermocellum that encodes endoglucanase A. Sequences coding for the mature CelA protein were fused in frame to yeast promoters and secretion signals, introduced into different vectors and analyzed biochemically in yeast secretory mutants. Gene dosage had little effect, whereas expression from a weak promoter enhanced endoglucanase A secretion. In yeast secretory mutants, a major fraction of endoglucanase A piled up in the endoplasmic reticulum as a core glycosylated protein.