期刊
FREE RADICAL BIOLOGY AND MEDICINE
卷 47, 期 6, 页码 841-849出版社
ELSEVIER SCIENCE INC
DOI: 10.1016/j.freeradbiomed.2009.06.028
关键词
Cytochrome c; Superoxide; Nitric oxide; Peroxynitrite; Peroxidase activity; Phosphatidylcholine; Phosphatidylglycerol
资金
- Fundacao de Amparo a Pesquisa do Estado de Sao Paulo
- Conselho Nacional de Desenvolvimento Cientfico e Tecnologico (CNPq)
- INCT Redoxome (CNPq/MCT)
- International Foundation for Science
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.
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