PROTEIN DISULFIDE-ISOMERASE OVEREXPRESSION INCREASES SECRETION OF FOREIGN PROTEINS IN SACCHAROMYCES-CEREVISIAE

Overexpression of protein disulfide isomerase (PDI) from a single chro mosomally integrated copy in Saccharomyces cerevisiae results in ten-f old higher levels of secretion of human platelet derived growth factor B homodimer, and a four-fold increase in secretion of Schizosaccharom yces pombe acid phosphatase. This result provides evidence that ineffi cient protein folding limits the secretion of some heterologous protei ns, and that manipulation of the endoplasmic reticulum lumenal environ ment can help overcome this limitation.