Q-band resonance Raman spectra of oxidized and reduced mitochondrial bc1 complexes.
Recently published crystallographic studies of mitochondrial bc1 complexes have stimulated renewed interest in the active site architecture 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 bL,bH, and c1 sites to be assessed. The spectra of the b hemes are particularly noteworthy. They exhibit evidence for a protonation equilibrium involving heme axial ligands and reveal a marked structural heterogeneity at the heme bH site that most likely involves nonplanar distortions of the macrocycle. The possible implications of these findings for heme functionality are discussed.
Gao
F
F
Department of Chemistry, University of New Mexico, Albuquerque 87131 USA.
Qin
H
H
Knaff
D B
DB
Zhang
L
L
Yu
L
L
Yu
C A
CA
Ondrias
M R
MR
D000818:Animals; D001665:Binding Sites; D002417:Cattle; D014450:Electron Transport Complex III / Q000737:chemistry* / Q000378:metabolism*; D006418:Heme / Q000737:chemistry / Q000378:metabolism; D008929:Mitochondria, Heart / Q000201:enzymology*; D010084:Oxidation-Reduction; D011487:Protein Conformation; D016354:Rhodobacter capsulatus / Q000201:enzymology; D013059:Spectrum Analysis, Raman
D006418:Heme; D014450:Electron Transport Complex III