Fluorescent Probes for Cytochrome P450 Structural Characterization and Inhibitor Screening

We have synthesized two luminescent probes (D-4-Ad and D-8-Ad) that target cytochrome P450cam. D-4-Ad luminescence is quenched by Förster energy transfer upon binding (K_d = 0.83 μM) but is restored when the probe is displaced from the active site by camphor. In contrast, D-8-Ad (K_d ≈ 0.02 μM) is not displaced from the enzyme, even in the presence of a large excess of camphor. The 2.2 Å resolution crystal structure of the D-8-Ad:P450cam complex reveals extensive hydrophobic contacts between the probe and the enzyme, which result from the conformational flexibility of the B‘, F, and G helices. Probes with properties similar to those of D-4-Ad potentially could be useful for screening P450 inhibitors

Conjugates of Heme-Thiolate Enzymes with Photoactive Metal-Diimine Wires

Heme-thiolate enzymes, notably cytochromes P450 and nitric oxide synthases, use dioxygen to oxygenatesubstrates. Photoactive metal-diimine molecular wires that are capable of effecting rapid redox state changesat buried active sites have been developed to generate intermediates in the catalytic cycles of these enzymes.Wires that feature a photoactive head group tethered to an active-site ligand bind P450CAM and induciblenitric oxide synthase (iNOS) primarily by hydrophobic interactions. The wire-binding specificity of eachenzyme is critically dependent on the structural flexibility of the protein. P450CAM:wire conjugates canadopt open or partially open conformations, thereby accommodating a wide range of wires, whereas onlylong wires with smaller [Re(CO)_3(bpy)Im]^+ head groupsare able to bind tightly in the rigid active-site channel of iNOS. Dansyl-terminated molecular wires functionas highly sensitive and isoform specific fluorescent sensors for P450CAM

Conjugates of Heme-Thiolate Enzymes with Photoactive Metal-Diimine Wires

Heme-thiolate enzymes, notably cytochromes P450 and nitric oxide synthases, use dioxygen to oxygenatesubstrates. Photoactive metal-diimine molecular wires that are capable of effecting rapid redox state changesat buried active sites have been developed to generate intermediates in the catalytic cycles of these enzymes.Wires that feature a photoactive head group tethered to an active-site ligand bind P450CAM and induciblenitric oxide synthase (iNOS) primarily by hydrophobic interactions. The wire-binding specificity of eachenzyme is critically dependent on the structural flexibility of the protein. P450CAM:wire conjugates canadopt open or partially open conformations, thereby accommodating a wide range of wires, whereas onlylong wires with smaller [Re(CO)_3(bpy)Im]^+ head groupsare able to bind tightly in the rigid active-site channel of iNOS. Dansyl-terminated molecular wires functionas highly sensitive and isoform specific fluorescent sensors for P450CAM