Efficient Secretion and Processing of Heterologous Proteins in Saccharomyces cerevisiae Is Mediated Solely by the Pre-Segment of α-Factor Precursor

A novel processing site was identified in fusions of the α-factor precursor of Saccharomyces cerevisiae following its 19 amino-terminal residues (pre-segment). Fusions of the pre-segment to heterologous proteins, including aminoglycoside phosphotransferase (APH) and human granulocyte-macrophage colony stimulating factor (hGM-CSF), were as efficiently secreted and processed as corresponding pre-pro fusions. Pre- and pre-pro fusions to hGM-CSF were identically N- and O-glycosylated. While pre-pro fusions to interleukin- 1β were not cleaved, pre-fusions were correctly processed during secretion. The high secretion efficiency of pre-fusions suggests that the pro-segment of the α-factor precursor is not required for efficient secretion and processing of protein fusions.