title: NMR basis for interprotein electron transfer gating between cytochrome c and cytochrome c oxidase.
abstract: The final interprotein electron transfer (ET) in the mammalian respiratory chain, from cytochrome c (Cyt c) to cytochrome c oxidase (CcO) is investigated by (1)H-(15)N heteronuclear single quantum coherence spectral analysis. The chemical shift perturbation in isotope-labeled Cyt c induced by addition of unlabeled CcO indicates that the hydrophobic heme periphery and adjacent hydrophobic amino acid residues of Cyt c dominantly contribute to the complex formation, whereas charged residues near the hydrophobic core refine the orientation of Cyt c to provide well controlled ET. Upon oxidation of Cyt c, the specific line broadening of N-H signals disappeared and high field (1)H chemical shifts of the N-terminal helix were observed, suggesting that the interactions of the N-terminal helix with CcO are reduced by steric constraint in oxidized Cyt c, while the chemical shift perturbations in the C-terminal helix indicate notable interactions of oxidized Cyt c with CcO. These results suggest that the overall affinity of oxidized Cyt c for CcO is significantly, but not very much weaker than that of reduced Cyt c. Thus, electron transfer is gated by dissociation of oxidized Cyt c from CcO, the rate of which is controlled by the affinity of oxidized Cyt c to CcO for providing an appropriate electron transfer rate for the most effective energy coupling. The conformational changes in Lys13 upon CcO binding to oxidized Cyt c, shown by (1)H- and (1)H, (15)N-chemical shifts, are also expected to gate intraprotein ET by a polarity control of heme c environment.
authors: Hokkaido University, Sapporo, Japan.
authors: Koichi
authors: K
authors: Sakamoto
authors: Masakatsu
authors: M
authors: Kamiya
authors: Mizue
authors: M
authors: Imai
authors: Kyoko
authors: K
authors: Shinzawa-Itoh
authors: Takeshi
authors: T
authors: Uchida
authors: Keiichi
authors: K
authors: Kawano
authors: Shinya
authors: S
authors: Yoshikawa
authors: Koichiro
authors: K
authors: Ishimori
mesh_terms: D000818:Animals; D001665:Binding Sites; D002417:Cattle; D045304:Cytochromes c / Q000737:chemistry* / Q000378:metabolism*; D004579:Electron Transport; D003576:Electron Transport Complex IV / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D010084:Oxidation-Reduction; D054730:Protein Interaction Domains and Motifs; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism
chemical_list: D011994:Recombinant Proteins; D045304:Cytochromes c; D003576:Electron Transport Complex IV