Q-BAND RESONANCE RAMAN-SPECTRA OF OXIDIZED AND REDUCED MITOCHONDRIAL BC(1) COMPLEXES

Recently published crystallographic studies of mitochondrial bc(1) com plexes have stimulated renewed interest in the active site architectur e of these important integral membrane proteins. We present resonance Raman spectra obtained via variable excitation within the heme Q-band from samples poised in several different net redox states. Appropriate subtraction and polarization analysis allows the vibrational behavior of the individual heme b(L), b(H), and c(1) sites to be assessed. The spectra of the b hemes are particularly noteworthy. They exhibit evid ence for a protonation equilibrium involving heme axial ligands and re veal a marked structural heterogeneity at the heme bH site that most l ikely involves nonplanar distortions of the macrocycle. The possible i mplications of these findings for heme functionality are discussed.