Validation of the Hsp150 polypeptide carrier and HSP150 promoter in expression of rat alpha2,3-sialyltransferase in yeasts.

Heterologous glycoproteins usually do not fold properly in yeast cells and fail to leave the endoplasmic reticulum. Here we show that the Hsp150Delta polypeptide carrier promoted proper folding and secretion of the catalytic ectodomain of rat alpha2,3-sialyltransferase (ST3Ne) in Pichia pastoris. The efficiency of the Hsp150Delta carrier in P. pastoris and Saccharomyces cerevisiae was at least as high as that of the MFalpha carrier. Most of Hsp150Delta-ST3Ne and MFalpha-ST3Ne remained noncovalently attached to the cell wall via the ST3Ne portion. The strength of the HSP150 promoter was found to be comparable to that of the GAL1 promoter.