BINDING AND ELECTRON-TRANSFER BETWEEN PUTIDAREDOXIN AND CYTOCHROME P450CAM - THEORY AND EXPERIMENTS

We present a detailed atomic level view of the interactions between cy tochrome P450cam (CYP101) and its natural redox partner, putidaredoxin (Pdx). A combined theoretical (Poisson-Boltzmann electrostatic calcul ations, electron transfer pathways, and molecular dynamics) and experi mental (site-directed mutagenesis and kinetic analysis) study is used to pinpoint surface residues in both proteins that are important for e lectron transfer, binding, or both. We find a situation where the elec trostatically complementary regions at the surface of both proteins ov erlap strongly with regions that have large electron transfer coupling s to the redox centers. This means that a small surface patch in each protein is involved in binding and electron transfer. A dominant elect ron transfer pathway is identified, corresponding to an electron leavi ng the reduced Fe2S2 in Pdx, going through Cys39 and Asp38, and transf erring across the interprotein interface to Arg112 (CYP101), then to a hemi: propionate group, and finally to the heme iron center.