The cytochrome P450s catalyze the oxidation of a wide variety of xenobiotic and endogenous compounds. Biochemical, biophysical, and computational approaches are applied to examine the structure-function relationships which govern the interactions of P450s with substrates, inhibitors, membrane lipids, and microsomal proteins. Since these interactions modulate P450 activity, elucidation of their molecular mechanism will aid in (1) clarifying the mechanism of P450-mediated drug and carcinogen metabolism; (2) defining the role of individual P450s in the metabolism of endogenous and environmental chemicals; and (3) development of specific P450 inhibitors. The flash photolysis technique was used to examine the kinetics of CO binding to P450. Although monoexponential kinetics were observed for P450 2E1, P450s 3A4 and 1A1 exhibited nonexponential kinetics. The Maximum Entropy Method was applied to obtain a kinetic distribution profile that corresponds to the conformational landscape. This statistical approach yielded P450-specific conformer distributions that were altered by substrate addition. These results suggest that P450 structure may be best viewed as a distribution of different conformers. Homology modeling was employed to generate a structure for human P450 1A2. On the basis of proposed active groups in the substrate binding site, we computationally searched a small molecule database for complementary molecules. This approach successfully identified several P450 inhibitors, thus providing further validation of our P450 homology model.
