The synthesis and processing of pea legumin in saccharomyces cerevisiae

Abstract

An expression vector utilising the promoter from the yeast phosphoglycerate kinase gene and a complete protein-encoding sequence, was used to direct the expression of the pea seed storage protein, legumin, in yeast (Sciccharomyces cerevisicie) . Levels of expression of between 1.95 and 2.24% total cellular protein were obtained. The legumin polypeptide expressed in yeast has an estimated M(_r). of 59,000. In plants, the legumin precursor polypeptide is processed by co-translational proteolysis to remove a "leader" sequence and by post-translational proteolysis to generate the mature disulphide-1inked x + β polypeptides (approximate M-.'s of 38,000 and 21,000 respectively).Although "leader" sequence removal in yeast may take place, post-translational proteolysis to generate the two smaller sub-units does not occur.