Figure 3.
Expression of L1 protein in shake flasks. (a and b) HPV L1 protein was constitutively secreted to the culture media or intracellularly produced after cultivation of four P. pastoris clones (two clones for each PPGK1-based vector) with glucose for 72 hours. Upon boiling, multimerization of L1 protein in the protein extract was observed as a protein smear, which was overcome after denaturation at 75°C. Aliquots of HPV16 L1 protein episomally expressed in P. pastoris [13] were used as a positive control (C+), while the protein extracts from P. pastoris strains transformed with the parental vectors were used as negative control (C−).