Allosteric Interactions in Human Cytochrome P450 CYP3A4: The Role of Phenylalanine 213

The role of Phe213 in the allosteric mechanism of human cytochrome P450 CYP3A4 was studied using a combination of progesterone (PGS) and carbamazepine (CBZ) as probe substrates. We expressed, purified, and incorporated into POPC Nanodiscs three mutants, F213A, F213S, and F213Y, and compared them with wild-type (WT) CYP3A4 by monitoring spectral titration, the rate of NADPH oxidation, and steady-state product turnover rates with pure substrates and substrate mixtures. All mutants demonstrated higher activity with CBZ, lower activity with PGS, and a reduced level of activation of CBZ epoxidation by PGS, which was most pronounced in the F213A mutant. Using all-atom molecular dynamics simulations, we compared the dynamics of WT CYP3A4 and the F213A mutant incorporated into the lipid bilayer and the effect of the presence of the PGS molecule at the allosteric peripheral site and evaluated the critical role of Phe213 in mediating the heterotropic allosteric interactions in CYP3A4.