Title
Effect of Heme Iron Valence State on the Conformation of Cytochrome c and Its Association with Membrane Interfaces
Author
Iseli L. Nantes, Maria R. Zucchi, Otaciro R. Nascimento, Adelaide Faljoni-Alario
Year
2000
Journal
The Journal of Biological Chemistry
Abstract
Recently cytochrome c has been mentioned as an important mediator in the events of cellular oxidative stress and apoptosis. To investigate the influence of charged interfaces on the conformation of cytochrome c, the CD and magnetic circular dichroic behavior of ferric and ferrous cytochromec in homogeneous medium and in phosphatidylcholine/phosphatidylethanolamine/cardiolipin and dicetylphosphate liposomes was studied in the 300–600 and 200–320 nm wavelength region. EPR spectra demonstrate that the association of cytochrome c with membranes promotes alterations of the crystal field symmetry and spin state of the heme Fe3+. The studies also include the effect of Pi, NaCl, and CaCl2. Magnetic circular dichroism and CD results show that the interaction of both ferrous and ferric cytochrome cwith charged interfaces promotes conformational changes in the α-helix content, tertiary structure, and heme iron spin state. Moreover, the association of cytochrome c with different liposomes is sensitive to the heme iron valence state. The more effective association with membranes occurs with ferrous cytochromec. Dicetylphosphate liposomes, as a negatively charged membrane model, promoted a more pronounced conformational modification in the cytochrome c structure. A decrease in the lipid/protein association is detected in the presence of increasing amounts of CaCl2, NaCl, and Pi, in response to the increase of the ionic strength.
Full Article
Instrument
J-720
Keywords
Circular dichroism, Magnetic circular dichroism, Secondary structure, Vesicle interactions, Coordination chemistry, Biochemistry