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Electron transfer between yeast cytochrome bc(1) complex and cytochrome c: a structural analysis.
Carola Hunte1, Sozanne Solmaz, Christian Lange
1Max-Planck-Institute of Biophysics, Dept. Molecular Membrane Biology, Heinrich-Hoffmann-Str. 7, 60528 Frankfurt/M., Germany. Carola.Hunte@mpibp-frankfurt.mpg.de
Biochimica Et Biophysica Acta
|September 11, 2002
Summary
The structure of yeast cytochrome c (CYC) bound to the cytochrome bc(1) complex (QCR) reveals optimal features for transient electron transfer. Key interactions include cation-pi and electrostatic forces, facilitating rapid heme-to-heme electron transfer.
Area of Science:
- Biochemistry
- Structural Biology
- Molecular Biophysics
Background:
- Cytochrome c (CYC) and the cytochrome bc(1) complex (QCR) are crucial for cellular respiration.
- Understanding their interaction is key to elucidating electron transfer mechanisms.
Purpose of the Study:
- To determine the high-resolution structure of the yeast CYC-QCR complex.
- To analyze the molecular interactions governing CYC binding and electron transfer.
Main Methods:
- X-ray crystallography of the CYC-QCR complex with an antibody fragment at 2.97 A resolution.
- Analysis of structural features, including hydrophobic interactions, cation-pi interactions, and electrostatic forces.
- Kinetic studies measuring cytochrome c reduction dependence on ionic strength.
Main Results:
- The CYC-QCR complex structure reveals a compact contact site with a central cation-pi interaction and stabilizing peripheral electrostatic patches.
- Electron transfer is optimized for transient interactions, with rapid reduction facilitated by close heme proximity.
- CYC binds to one site on the homodimeric QCR, influenced by ubiquinone presence and showing less ionic strength dependence in yeast compared to other sources.
Conclusions:
- The determined structure provides insights into the transient nature of the CYC-QCR electron transfer complex.
- Specific interactions dictate substrate binding and orientation, crucial for efficient electron transfer.
- Regulatory mechanisms involving binding site occupancy and ubiquinone presence are suggested.