In cellular respiration, cytochrome c transfers electrons from the cytochrome bc1 complex to cytochrome c oxidase by transiently binding to the membrane proteins. The first X-ray structure of the yeast cytochrome bc1 complex with bound cytochrome c revealed the general architecture of the electron-transfer complex. The interface of the complex is small. The haem moieties are centrally located in a mainly non-polar contact site, which includes a cation–π interaction and is surrounded by complementary charged residues. Only one cytochrome c1-docking site of the dimeric complex is occupied with cytochrome c. The recent 1.9 Å (1 Å=0.1 nm) resolution structure of the complex showed that the interface is highly hydrated. With cytochrome c bound, a higher number of interfacial water molecules are present on the cytochrome c1 interface, whereas its protein surface is not affected. Remarkably, the dimer structure is slightly asymmetric. Univalent cytochrome c binding coincides with conformational changes of the Rieske head domain and subunit QCR6p. Pronounced hydration and a mobility mismatch at the interface with disordered charged residues on the cytochrome c side are favourable for transient binding. Comparison with a new structure of the complex with bound isoform-2 cytochrome c led to the definition of a core interface, which refers to four common interaction pairs including the cation–π interaction. They encircle the haem groups and are surrounded by variable interactions. The core interface may be a feature to gain specificity for formation of the reactive complex. The consistency in the binding interaction despite differences in primary sequence, redox state and crystal contacts, together with crystallization at physiological ionic strength, clearly suggest that the structures show the native bound state of the electron-transfer complex.
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October 2008
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Conference Article|
September 19 2008
A structural analysis of the transient interaction between the cytochrome bc1 complex and its substrate cytochrome c
Ajeeta Nyola;
Ajeeta Nyola
*Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, Max-von-Laue-Strasse 3, D-60438 Frankfurt am Main, Germany
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Carola Hunte
Carola Hunte
1
†Institute of Membrane and Systems Biology, University of Leeds, Leeds LS2 9JT, U.K.
‡Center of Excellence ‘Macromolecular Complexes’, Johann Wolfgang Goethe-Universität, D-60590 Frankfurt am Main, Germany
1To whom correspondence should be addressed (email [email protected]).
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Publisher: Portland Press Ltd
Received:
July 02 2008
Online ISSN: 1470-8752
Print ISSN: 0300-5127
© The Authors Journal compilation © 2008 Biochemical Society
2008
Biochem Soc Trans (2008) 36 (5): 981–985.
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Received:
July 02 2008
Citation
Ajeeta Nyola, Carola Hunte; A structural analysis of the transient interaction between the cytochrome bc1 complex and its substrate cytochrome c. Biochem Soc Trans 1 October 2008; 36 (5): 981–985. doi: https://doi.org/10.1042/BST0360981
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