Electrochemistry of Cytochrome P450 BM3 in Sodium Dodecyl Sulfate Films

Direct electrochemistry of the cytochrome P450 BM3 heme domain (BM3) was achieved by confining the protein within sodium dodecyl sulfate (SDS) films on the surface of basal-plane graphite (BPG) electrodes. Cyclic voltammetry revealed the heme Fe^(III/II) redox couple at −330 mV (vs Ag/AgCl, pH 7.4). Up to 10 V/s, the peak current was linear with the scan rate, allowing us to treat the system as surface-confined within this regime. The standard heterogeneous rate constant determined at 10 V/s was estimated to be 10 s^(-1). Voltammograms obtained for the BM3−SDS−BPG system in the presence of dioxygen exhibited catalytic waves at the onset of Fe^(III) reduction. The altered heme reduction potential of the BM3−SDS−graphite system indicates that SDS is likely bound in the enzyme active-site region. Compared to other P450-surfactant systems, we find redox potentials and electron-transfer rates that differ by ∼100 mV and >10-fold, respectively, indicating that the nature of the surfactant environment has a significant effect on the observed heme redox properties.