Intermolecular electron transfer in cytochrome P450cam covalently bound with Tris(2,2′-bipyridyl)ruthenium(II): structural changes detected by FTIR spectroscopy

Abstract

Using Fourier transform infrared spectroscopy (FTIR) we have monitored the changes in the protein structure following photoinduced electron transfer from Ru(bpy) 3 2+ covalently attached to cysteine 334 on the surface of cytochrome P450cam (CYP101). The FTIR difference spectra between the oxidized and reduced form indicate changes in a salt link and the secondary structure (α-helix and turn regions). Photoreduction was carried out in the presence of carbon monoxide in order to prove the reduction of the heme iron by means of the appearance of the characteristic CO stretch vibration infrared band at 1940 cm −1 for the camphor-bound protein. This infrared band has also been used to estimate electron transfer rates. The observed rates depend on the protein concentration, indicating that intermolecular electron transfer occurs between the labeled molecules.