Detection of Heme-Distortions in Ferri- and Ferrocyto-Chrome C by Resonance Raman Scattering

Abstract

We have measured the depolarization ratio and polarized intensities of the oxidation marker A_1g-Raman line at 1363 cm^?1 and 1375 cm^?1 in ferri- and ferrocytochrome c respectively. From these data we derive symmetry classified distortions of the heme group from its ideal D_4h-symmetry. In ferrocytochrome c these distortions are independent of the pH-value of the solution, indicating that the heme environment is stable with respect to pH. In ferricytochrome c we observe pH-dependent changes of the distortions, indicating the well known conformational change with pK = 9.05, where the methionine 80 ligand is replaced by lysine-79. The data indicate that in this conformation due to opening of the heme crevice the heme group has a higher effective symmetry.