EXPERIENCE WITH THE CLONING AND EXPRESSION OF CLONED GENES IN SACCHAROMYCES CEREVISIAE SUGGESTS THAT THE RECOVERED YIELD OF CORRECTLY FOLDED PROTEIN PRODUCT IS GREATLY IMPROVED BY THE USE OF A YEAST-SECRETION PROCESS.

EXPERIENCE WITH THE CLONING AND EXPRESSION OF CLONED GENES IN SACCHAROMYCES CEREVISIAE SUGGESTS THAT THE RECOVERED YIELD OF CORRECTLY FOLDED PROTEIN PRODUCT IS GREATLY IMPROVED BY THE USE OF A YEAST-SECRETION PROCESS. THIS IS ESPECIALLY TRUE FOR PROTEINS THAT ARE NORMALLY SECRETED FROMTHEIR NATURAL CELL SOURCES. THUS, COLLABORATIVE RESEARCH WILL FUSE THE GENE FOR HUMAN PROINSULIN TO A VARIETY OF YEAST PROMOTER AND SECRETION SIGNAL SEQUENCES AND EXPRESS ITIN YEAST IN AN ATTEMPT TO ISOLATE A STRAIN THAT SECRETES COMMERCIALLY VIABLE AMOUNTS OF PROINSULIN. A NUMBER OF MUTANT YEAST STRAINS ARE AVAILABLE THAT HAVE AN INCREASED CAPACITY FOR THE SECRETION OF FOREIGN PROTEINS. THESE SUPERSECRETING STRAINS WILL BE TESTED FOR THEIR EFFICACY IN SECRETING PROINSULIN. ONCE REASONABLE YIELDS OF SECRETED PROINSULIN ARE OBTAINED, THE PROINSULIN'S STRUCTURE WILL BE ANALYZED IN TERMS OF DISULFIDE BOND CONTENT, AMINO TERMINAL PROCESSING, AND CONVERTABILITY TO INSULIN.