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

- The distal F240A mutation alters the hydroxylation activity of rat CYP1A1 towards two persistent organic pollutants (POPs) in opposing ways.
- Both POPs have a high affinity for lipid membranes, from which they can enter the active site via channels capped by F/A 240.
- The distal F240A mutation enabled efficient binding and positioning of TCDD in the CYP1A1 active site.
- The F240A mutation destabilizes the binding of PCB77 by CYP1A1 and reduces the enzyme's hydroxylation activity towards this substrate.
- Both active site mutations and distal mutations can be exploited in rational enzyme design.

BackgroundCytochromes 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.MethodsWe 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.ResultsWe 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 significanceAmino acids that affect substrate access channels can be viable targets for rational enzyme design even if they are located far from the catalytic site.

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