open access

https://hdl.handle.net/2115/48142

NMR basis for interprotein electron transfer gating between cytochrome c and cytochrome c oxidase

英語

redox-dependent interaction

2011-07-26

National Academy of Sciences

Proceedings of the National Academy of Sciences of the United States of America

108(30)

12271-12276

The final interprotein electron transfer (ET) in the mammalian respiratory chain, from cytochrome c (Cyt c) to cytochrome c oxidase (CcO) is investigated by 1H-15N 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 1H 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 1H- and 1H, 15N-chemical shifts, are also expected to gate intraprotein ET by a polarity control of heme c environment.

学術雑誌論文

Accepted Manuscript

0027-8424