Physiological regulation, xenobiotic induction, and heterologous expression of P450 monooxygenase gene pc-3 (CYP63A3), a new member of the CYP63 gene cluster in the white-rot fungus Phanerochaete chrysosporium.

In order to characterize the functional diversity in CYP63 cluster of tandemly linked P450 genes (pc-1, pc-2, and pc-3) in Phanerochaete chrysosporium, here we report the functional characterization of pc-3 (CYP63A3), a newly cloned member of this group. pc-3 expression was favored in nutrient-limited versus nutrient-rich media in 3-6-day-old cultures and was upregulated by starch as a carbon source or by oxygenation of cultures. pc-3 was induced by various xenobiotics in defined nutrient-limited (3-9-fold) and nutrient-rich (2-5-fold) cultures. Particularly, a range of unsubstituted and substituted aliphatic hydrocarbons (alkanes and fatty acids) induced the expression under the two nutrient conditions albeit in a differential manner. Interestingly, pc-3 was also inducible by certain oxygenated mono aromatics (nitrophenol, benzoate, and resorcinol), lower molecular weight (2 to 4 ring size) polycyclic aromatic hydrocarbons (PAHs) and alkali-treated lignin derivatives in nutrient-rich malt extract cultures. The study further establishes that the three CYP63 genes (CYP63A1, A2, and A3) are independently regulated despite being members of the tandem gene cluster with high gene structural similarity (13-14 introns) and protein sequence homology (59-85%). The pc-3 cDNA (1,812 bp) was expressed in E. coli as a His-tagged protein (approximately 74 kDa). This constitutes the first report on heterologous expression of a P450 monooxygenase enzyme from this model white-rot fungus.