title: A spin label study of conformational changes in cytochrome c.
abstract: Spin-labeled pig heart cytochromes c singly modified at Met-65, Tyr-74 and at one of the lysine residues, Lys-72 or Lys-73, were investigated by the ESR method under conditions of different ligand and redox states of the heme and at various pH values. Replacement of Met-80 by the external ligand, cyanide, was shown to produce a sharp increase in the mobility of all the three bound labels while reduction of the spin-labeled ferricytochromes c did not cause any marked changes in their ESR spectra. In the pH range 6-13, two conformational transitions in ferricytochrome c were observed which preceded its alkaline denaturation: the first with pK 9.3 registered by the spin label at the Met-65 position, and the second with pK 11.1 registered by the labels bound to Tyr-74 and Lys-72(73). The conformational changes in the 'left-hand part' of ferricytochrome c are most probably induced in both cases by the exchange of internal protein ligands at the sixth coordination site of the heme.
mesh_terms: D000818:Animals; D003574:Cytochrome c Group / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D006736:Horses; D008958:Models, Molecular; D009206:Myocardium; D011487:Protein Conformation; D013113:Spin Labels; D013552:Swine
chemical_list: D003574:Cytochrome c Group; D013113:Spin Labels