Effect of Lanthanum on Expression of Recombinant Allophycocyanin Gene in Pichia Pastoris

The enhancing effect of lanthanum on gene expression of recombinant allophycocyanin （rAPC）, a potential antitumor medicine, in Pichia pastoris was studied. PCR and sequence analysis were used in order to prove whether the APC gene had integrated into the yeast genome. The expression level of the recombinant allophycocyanin （rAPC） in BMMY medium containing LaCl3 was detected by ELISA method. The recombinant allophycocyanin was determined by Western blot. The results show that the recombinant Pichia pastoris chromosome contained allophycocyanin gene. Expression efficiency of rAPC gene in Pichia pastoris was promoted by proper LaCl3 concentration like 2, 5, 10 mmol·L-1, among which 5 (mmol·L-1) was the most effective. The highest expression yield of rAPC in the BMMY medium containing 5 mmol·L-1 LaCl3 was 44 mg·L-1 at 48 h, that was increased by 110% compared with 2.1 mg·L-1 of control, in the meantime, the optimum culture time is shortened from 72 to 48 h. The result of western blot analysis indicates that the rAPC consisted of two kinds of subunits with molecular weight of 19 and 21 kDa respectively.