Modeling of Anopheles minimus Mosquito NADPH-Cytochrome P450 Oxidoreductase (CYPOR) and Mutagenesis Analysis

Abstract: Malaria is one of the most dangerous mosquito-borne diseases in many tropical countries, including Thailand. Studies in a deltamethrin resistant strain of Anopheles minimus mosquito, suggest cytochrome P450 enzymes contribute to the detoxification of pyrethroid insecticides. Purified A. minimus CYPOR enzyme (AnCYPOR), which is the redox partner of cytochrome P450s, loses flavin-adenosine di-nucleotide (FAD) and FLAVIN mono-nucleotide (FMN) cofactors that affect its enzyme activity. Replacement of leucine residues at positions 86 and 219 with phenylalanines in FMN binding domain increases FMN binding, enzyme stability, and cytochrome c reduction activity. Membrane-Bound L86F/L219F-AnCYPOR increases A. minimus P450-mediated pyrethroid metabolism in vitro. In this study, we constructed a comparative model structure of AnCYPOR using a rat CYPOR structure as a template. Overall model structure is similar to rat CYPOR, with some prominent differences. Based on primary sequence and structural analysis of rat and A. minimus CYPOR, C427R, W678A, and W678H mutations were generated together with L86F/L219F resulting in three soluble Δ55 triple mutants. The C427R triple AnCYPOR mutant retained a higher amount of FAD bindin

Distal effect of amino acid substitutions in CYP2C9 polymorphic variants causes differences in interatomic interactions against (S)-warfarin.

Cytochrome P450 2C9 (CYP2C9) is crucial in excretion of commonly prescribed drugs. However, changes in metabolic activity caused by CYP2C9 polymorphisms inevitably result in adverse drug effects. CYP2C9*2 and *3 are prevalent in Caucasian populations whereas CYP2C9*13 is remarkable in Asian populations. Single amino acid substitutions caused by these mutations are located outside catalytic cavity but affect kinetic activities of mutants compared to wild-type enzyme. To relate distal effects of these mutations and defective drug metabolisms, simulations of CYP2C9 binding to anti-coagulant (S)-warfarin were performed as a system model. Representative (S)-warfarin-bound forms of wild-type and mutants were sorted and assessed through knowledge-based scoring function. Interatomic interactions towards (S)-warfarin were predicted to be less favorable in mutant structures in correlation with larger distance between hydroxylation site of (S)-warfarin and reactive oxyferryl heme than wild-type structure. Using computational approach could delineate complication of CYP polymorphism in management of drug therapy

Discrimination of near native-like (<i>S</i>)-warfarin-bound complex from stable conformations obtained from MD simulations.

<p>A set of conformations of (<i>S</i>)-warfarin-bound complex were generated by MD simulations. Near native-like complex of each variant was sorted from the set of conformations by knowledge-based distribution functions that consider interatomic contacts at varied distances. The distance bins are derived from interatomic contacts between small molecules and proteins deposited in Cambridge Structural Database (CSD).</p

Comparison of r⋅m⋅r scores of residues that are involved in interaction with (<i>S</i>)-warfarin.

<p>Residues involved in binding with (<i>S</i>)-warfarin are scored and classified based on 6 SRSs comprising ligand binding site of CYPs. Favorable interaction is represented by negative score value. Wild-type and mutant residues are designated by different shading of bars.</p