SECRETORY EXPRESSION OF A SINGLE-CHAIN INSULIN PRECURSOR IN YEAST ANDITS CONVERSION INTO HUMAN INSULIN

A synthetic single-chain porcine insulin precursor (PIP) gene and an c r-mating factor leader sequence (alpha MFL) gene obtained by the PCR m ethod are inserted between the promoter and 3'-terminating sequence of the alcohol dehydrogenase gene ADH1 in plasmid pVT102-U to form plasm id pVT102-U/alpha MFL-PIP. The single-chain insulin precursor is expre ssed and secreted to the culture medium by Saccharomyces cerevisiae tr ansformed by pVT102-U/alpha MFL-PIP. The precursor is purified and con verted into human insulin by tryptic transpeptidation. The purified hu man insulin is fully active and on be crystallized. The overall yield of human insulin is 25 mg per liter of culture medium.