Molecular insights into the role of a distal F240A mutation that alters CYP1A1 activity towards persistent organic pollutants

Background: Cytochromes P450 are major drug-metabolizing enzymes involved in the biotransformation of diverse xenobiotics and endogenous chemicals. Persistent organic pollutants (POPs) are toxic hydrophobic compounds that cause serious environmental problems because of their poor degradability. This calls for rational design of enzymes capable of catalyzing their biotransformation. Cytochrome P450 1A1 isoforms catalyze the biotransformation of some POPs, and constitute good starting points for the design of biocatalysts with tailored substrate specificity. Methods: We rationalized the activities of wild type and mutant forms of rat cytochrome P450 1A1 towards 2,3,7,8-tetrachloro-dibenzo-p-dioxin (TCDD) and 3,3',4,4'-tetrachlorobiphenyl (PCB77) using experiments and molecular dynamics simulations. Results: We showed that the enhanced activity of the CYP1A1 mutant towards TCDD was due to more efficient binding of the substrate in the active site even though the mutated site was over 2.5 nm away from the catalytic center. Moreover, this mutation reduced activity towards PCB77. General significance: Amino acids that affect substrate access channels can be viable targets for rational enzyme design even if they are located far from the catalytic site.