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首页> 外文期刊>Bulletin of the Chemical Society of Japan >New Aspects of Cytochrome c: 3D Domain Swapping, Membrane Interaction, Peroxidase Activity, and Met80 Sulfoxide Modification
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New Aspects of Cytochrome c: 3D Domain Swapping, Membrane Interaction, Peroxidase Activity, and Met80 Sulfoxide Modification

机译:细胞色素C的新方面C:3D结构域交换,膜相互作用,过氧化物酶活性和Met80硫氧化物改性

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Cytochrome (cyt) c is a multifunctional water-soluble heme protein. It transfers electrons from the cyt bc(1) complex (Complex III) to cyt c oxidase (Complex IV) in the respiratory chain of mitochondria, and can trigger apoptosis as well. Although cyt c has been studied for more than a century, its new aspects are still being elucidated. For example, we found that cyt c molecules can form oligomers and polymers by 3D domain swapping (3D-DS), where the C-terminal alpha-helix is exchanged between molecules. 3D-DS is observed in other c-type cyts-although the swapping regions may differ-indicating that 3D-DS is a common feature for c-type cyts. 3D-DS of c-type cyt can occur during protein folding and expression in cells. The electron transfer ability of cyt c decreases by 3D-DS, due to the dissociation of Met80 from the heme iron, whereas the peroxidase activity increases. The cyt c electron transfer partners, Complex III and Complex IV, are embedded in the inner mitochondria membrane, whereas positively charged cyt c interacts with negatively charged cardiolipin (CL) molecules at the inner mitochondrial membrane. We have recently elucidated the CL-interaction site of cyt c at atomic level by NMR spectroscopy using CL-containing bicelles. The membrane interaction site of cyt c is relatively wide and similar to the interaction site for Complex III and Complex IV, indicating that cyt c interacts with lipid membranes and partner proteins in a similar way. When cyt c interacts strongly with CL, Met80 dissociates from the heme iron and the peroxidase activity of cyt c increases. We have shown that the proton concentration at the CL-containing membrane is higher than that in the bulk solution, which may enhance the peroxidase activity of cyt c. The Met80-dissociated cyt c has been shown to oxidize CL, increasing the permeability of cyt c through the membrane. We found that when Met80 is dissociated from the heme iron in cyt c, Met80 can be oxidized to methionine sulfoxide by the peroxidase reaction of the heme of cyt c or its reaction with molecular oxygen under reduced conditions. Met80-oxidized cyt c depicts a higher peroxidase activity compared to that of unmodified cyt c; thus Met80 oxidation may enhance lipid oxidation and eventually apoptosis. These new findings not only help in understanding the structure-function relationships of multifunctional cyt c but also show that there are still hidden properties in well-studied proteins.
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