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Title: Superoxide radical protects liposome-contained cytochrome c against oxidative damage promoted by peroxynitrite and free radicals
Authors: Mano, Camila M.
Barros, Marcelo P.
Faria, Priscila A.
Prieto, Tatiana
Dyszy, Fabio H.
Nascimento, Otaciro R.
Nantes, Iseli L.
Bechara, Etelvino J. H. [UNIFESP]
Universidade de São Paulo (USP)
Univ Cruzeiro Sul
Univ Mogi das Cruzes
Universidade Federal de São Paulo (UNIFESP)
Keywords: Cytochrome c
Nitric oxide
Peroxidase activity
Issue Date: 15-Sep-2009
Publisher: Elsevier B.V.
Citation: Free Radical Biology and Medicine. New York: Elsevier B.V., v. 47, n. 6, p. 841-849, 2009.
Abstract: The effects of nitrosative species on cyt c structure and peroxidase activity were investigated here in the presence of O(2)(center dot-) and anionic and zwitterionic vesicles. Nitrosative species were generated by 3-morpholinesydnonymine (SIN1) decomposition, using cyt c heme iron and/or molecular oxygen as electron acceptor. Far-and near-UV CD spectra of SIN1-treated cyt c revealed respectively a slight decrease of a-helix content (from 39 to 34%) and changes in the tryptophan structure accompanied by increased fluorescence. the Soret CD spectra displayed a significant decrease of the positive signal at 403 nm. EPR spectra revealed the presence of a low-spin cyt c form (S = 1/2) with g(1) = 2.736, g(2) = 2.465, and g(3) = 2.058 after incubation with SIN1. These data suggest that the concomitant presence of NO(center dot) and O(2)(center dot-) generated from dissolved oxygen, in a system containing cyt c and liposomes, promotes chemical and conformational modi. cations in cyt c, resulting in a hypothetical bis-histidine hexacoordinated heme iron. We also show that, paradoxically, O(2)(center dot-) prevents not only membrane lipoperoxidation by peroxide-derived radicals but also oxidation of cyt c itself due to the ability of O(2)(center dot-) to reduce heme iron. Finally, lipoperoxidation measurements showed that, although it is a more efficient peroxidase, SIN1-treated cyt c is not more effective than native cyt c in promoting damage to anionic liposomes in the presence of tert-ButylOOH, probably due to loss of affinity with negatively charged lipids. (C) 2009 Elsevier Inc. All rights reserved.
ISSN: 0891-5849
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