Q-band resonance Raman investigation of turnip cytochrome f and Rhodobacter capsulatus cytochrome c(1)

The results of a comprehensive Q-band resonance Raman investigation of cyto chrome cl and cytochrome f subunits of bc(1) and b(6)f complexes are presen ted. Q-band excitation provides a particularly effective probe of the local heme environments of these species. The effects of protein conformation (p articularly axial ligation) on heme structure and function were further inv estigated by comparison of spectra obtained from native subunits to those o f a site directed c(1) mutant (M183L) and various pH-dependent species of h orse heart cytochrome c. In general, all species examined displayed variabi lity in their axial amino acid ligation that suggests a good deal of flexib ility in their hemepocket conformations. Surprisingly, the large scale prot ein rearrangements that accompany axial ligand replacement have little or n o effect on macrocycle geometry in these species. This indicates the identi ty and/or conformation of the peptide linkage between the two cysteines tha t are covalently linked to the heme periphery may determine heme geometry. (C) 1999 Elsevier Science B.V. All rights reserved.