Effect of disruption of Pichia pastoris YPS1 gene on viability and production of recombinant proteins

In the present study, we constructed a Pichia pastoris mutant strain PS111 that lacks one member of the yapsin family through disruption of the YPS1 gene coding for aspartic protease yapsin 1. Under normal growth conditions, the PS111 mutant strain did not show detectable growth defects. Unlike the S. cerevisiae yps1 mutant, the P. pastoris PS111 strain showed no sensitivity when grown in the presence of CaCl₂, elevated temperature (37°C), under acid (pH 4.9) and alkaline (pH 8.3) conditions. Unlike the S. cerevisiae, the P. pastoris yps1 mutant showed decreased growth phenotype induced by cell wall-perturbing reagent sodium dodecyl sulfate (SDS) only when the concentration of SDS was increased by ten times. The use of the yps1 disruptant to produce human interferon alpha16 (hINF-α16) prevents proteolysis, which occurs in the wildtype strain. It was found that the degradation of recombinant protein Alburon composed of human serum albumin (HSA) and hINF-α16 was slightly decreased in the strain lacking yapsin 1.