Optimizing the human aryl hydrocarbon receptor (hAHR) expression in Pichia pastoris

The aryl hydrocarbon receptor (AHR) is a transcription factor which heterodimerizes with the aryl hydrocarbon receptor nuclear translocator (Arnt) to regulate downstream gene transcription. For the purpose of studying the crystal structure of human aryl hydrocarbon receptor (hAHR), it is essential to obtain abundant amount of pure recombinant protein.Basing on the benefits of using P. pastoris system to produce recombinant protein, including appropriate folding, secretion of interest proteins to the external environment of the cell, and easier purification process of protein due to the its limited production of endogenous secretory proteins [1], our lab chose P. pastoris yeast as the host to overexpress human AHR. My lab has successfully used the protease-deficient P. pastoris (ySMD1163) strain to express AHR [2], but unfortunately the yield is modest, presumably due to low copy number. My work addressed whether increasing the copy number of hAHR in the yeast genome would increase the expression level of hAHR in Pichia pastoris. Results from my experiments showed that although the copy number correlated with the expression levels of hAHR, the increased expression of the hAHR largely in the pellet, suggesting that the soluble expression of hAHR can’t be enhanced merely by increasing its production