3wc8 | pdb_00003wc8
Dimeric horse cytochrome c obtained by refolding with desalting method
Structural highlights
Function[CYC_HORSE] Electron carrier protein. The oxidized form of the cytochrome c heme group can accept an electron from the heme group of the cytochrome c1 subunit of cytochrome reductase. Cytochrome c then transfers this electron to the cytochrome oxidase complex, the final protein carrier in the mitochondrial electron-transport chain. Plays a role in apoptosis. Suppression of the anti-apoptotic members or activation of the pro-apoptotic members of the Bcl-2 family leads to altered mitochondrial membrane permeability resulting in release of cytochrome c into the cytosol. Binding of cytochrome c to Apaf-1 triggers the activation of caspase-9, which then accelerates apoptosis by activating other caspases (By similarity). Publication Abstract from PubMedWe have previously shown that horse cytochrome c (cyt c) forms oligomers by domain swapping its C-terminal alpha-helix when interacting with ethanol. Although folding of cyt c has been studied extensively, formation of domain-swapped oligomers of cyt c during folding has never been reported. We found that domain-swapped oligomeric cyt c is produced during refolding from its guanidinium ion-induced unfolded state at high protein concentrations and low temperatures. The obtained dimer exhibited a domain-swapped structure exchanging the C-terminal alpha-helical region between molecules. The extent of dimer formation decreased significantly for the folding of C-terminal cyt c mutants with reduced hydrophobicity achieved by replacement of hydrophobic residues with Gly in the C-terminal region, whereas a large amount of heterodimers was generated for the folding of a mixture of N- and C-terminal mutants. These results show that cyt c oligomers are formed through intermolecular hydrophobic interaction between the N- and C-terminal alpha-helices during folding. A slow phase (4-5 s) was observed in addition to a 400-500 ms phase during folding of a high concentration of cyt c in the presence of 1.17 M guanidine hydrochloride. The fast phase is attributed to the intramolecular ligand exchange process, and we attribute the slow phase to the ligand exchange process in oligomers. These results show that it is important to consider formation of domain-swapped oligomeric proteins when folding at high protein concentrations. Formation of Oligomeric Cytochrome c during Folding by Intermolecular Hydrophobic Interaction between N- and C-Terminal alpha-Helices.,Parui PP, Deshpande MS, Nagao S, Kamikubo H, Komori H, Higuchi Y, Kataoka M, Hirota S Biochemistry. 2013 Dec 3;52(48):8732-44. doi: 10.1021/bi400986g. Epub 2013 Nov, 20. PMID:24206001[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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