Use of the glyceraldehyde-3-phosphate dehydrogenase promotor for production of functional mammalian membrane transport proteins in the yeast Pichia pastoris

The promoter of the glyceraldehyde-3-phosphate dehydrogenase gene (P(GAP)) was employed to produce the mammalian peptide transporters hPEPT1 and rPEPT2 as models for polytopic transmembrane proteins in the methylotrophic yeast Prichia pastoris. Cells of a recombinant renal peptide transporter (rPEPT2) clone produced constitutively the functional carrier protein. The level of functional expression of rPEPT2 with P(GAP) varied depending on the carbon source used for cell growth, but was up to five times higher than that obtained with the commonly employed inducible alcohol oxidase 1 promoter (P(AOX1)). Similar results were obtained for the expression level of the human intestinal peptide transporter hPEPT1 controlled by either P(GAP) or P(AOX1). Therefore, the P(GAP) seems to be an attractive alternative to P(AOX1) for generation of transgenic P. pastoris cells expressing functional mammalian membrane transport proteins at high levels.