title: Active Site Structure and Peroxidase Activity of Oxidatively Modified Cytochrome c Species in Complexes with Cardiolipin.
abstract: We report a resonance Raman and UV-vis characterization of the active site structure of oxidatively modified forms of cytochrome c (Cyt-c) free in solution and in complexes with cardiolipin (CL). The studied post-translational modifications of Cyt-c include methionine sulfoxidation and tyrosine nitration, which lead to altered heme axial ligation and increased peroxidase activity with respect to those of the wild-type protein. In spite of the structural and activity differences between the protein variants free in solution, binding to CL liposomes induces in all cases the formation of a spectroscopically identical bis-His axial coordination conformer that more efficiently promotes lipid peroxidation. The spectroscopic results indicate that the bis-His form is in equilibrium with small amounts of high-spin species, thus suggesting a labile distal His ligand as the basis for the CL-induced increase in enzymatic activity observed for all protein variants. For Cyt-c nitrated at Tyr74 and sulfoxidized at Met80, the measured apparent binding affinities for CL are ∼4 times larger than for wild-type Cyt-c. On the basis of these results, we propose that these post-translational modifications may amplify the pro-apoptotic signal of Cyt-c under oxidative stress conditions at CL concentrations lower than for the unmodified protein.
authors.affiliation: Departamento de Química Inorgánica, Analítica y Química Física and INQUIMAE (CONICET-UBA), Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria , Pab. 2, piso 1, C1428EHA Buenos Aires, Argentina.
authors.forename: Daiana A
authors.initials: DA
authors.lastname: Capdevila
authors.affiliation: Departamento de Química Inorgánica, Analítica y Química Física and INQUIMAE (CONICET-UBA), Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria , Pab. 2, piso 1, C1428EHA Buenos Aires, Argentina.
authors.forename: Santiago
authors.initials: S
authors.lastname: Oviedo Rouco
authors.affiliation: Departamento de Bioquímica and Center for Free Radical and Biomedical Research, Facultad de Medicina, Universidad de la República , Montevideo, Uruguay.
authors.forename: Florencia
authors.initials: F
authors.lastname: Tomasina
authors.affiliation: Departamento de Bioquímica and Center for Free Radical and Biomedical Research, Facultad de Medicina, Universidad de la República , Montevideo, Uruguay.
authors.forename: Verónica
authors.initials: V
authors.lastname: Tortora
authors.affiliation: Departamento de Bioquímica and Center for Free Radical and Biomedical Research, Facultad de Medicina, Universidad de la República , Montevideo, Uruguay.
authors.forename: Verónica
authors.initials: V
authors.lastname: Demicheli
authors.affiliation: Departamento de Bioquímica and Center for Free Radical and Biomedical Research, Facultad de Medicina, Universidad de la República , Montevideo, Uruguay.
authors.forename: Rafael
authors.initials: R
authors.lastname: Radi
authors.affiliation: Departamento de Química Inorgánica, Analítica y Química Física and INQUIMAE (CONICET-UBA), Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria , Pab. 2, piso 1, C1428EHA Buenos Aires, Argentina.
authors.forename: Daniel H
authors.initials: DH
authors.lastname: Murgida
mesh_terms: D000818:Animals; D002308:Cardiolipins / Q000737:chemistry*; D020134:Catalytic Domain; D045304:Cytochromes c / Q000737:chemistry*; D006736:Horses; D011487:Protein Conformation; D013056:Spectrophotometry, Ultraviolet; D013059:Spectrum Analysis, Raman
chemical_list: D002308:Cardiolipins; D045304:Cytochromes c