A novel yeast secretion signal isolated from 28K killer precursor protein encoded on the linear DNA plasmid pGKL1

Abstract

Saccharomyces cerevisiae harboring linear dsDNA plasmids, pGKL1 and pGKL2, secretes a killer toxin consisting of 97, 31 and 28 kilodalton subunits (Nucleic Acids Res., 15, 1031-1046, 1987). We isolated the DNA encoding the N-terminal pre-sequence of the 28K precursor protein and constructed a new secretion vector in S. cerevisiae. Mouse .alpha.-amylase fused to the 28K signal sequence was secreted into the culture medium with a high efficiency similar to those fused to the mating factor .alpha. and 97K-31K killer signal sequences. This data clearly indicates that 28K presequence functions as a secretion signal. Glycosylated and non-glycosylated .alpha.-amylase molecules were detected in the culture medium. The secretion of .alpha.-amylase was blocked by sec18-1 mutation. The secreted .alpha.-amylase recovered from the medium was found to migrate faster in SDS-polyacrylamide gel than the precursor form of .alpha.-amylase synthesized in vitro. These lines of evidence suggest that mouse .alpha.-amylase fused to 28K killer signal sequence was processed, glycosylated and secreted through the normal secretion pathway of the yeast.