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Dynamic interaction of plastocyanin with the cytochrome bf complex
J Illerhaus1, L Altschmied, J Reichert
1Institut für Biologie II/Biochemie, Albert-Ludwigs-Universität Freiburg, Schänzlestrasse 1, D-79104 Freiburg, Germany.
The Journal of Biological Chemistry
|June 6, 2000
Summary
Mutant plastocyanin studies reveal distinct binding sites for the cytochrome bf complex, differing from photosystem I interactions. These findings clarify electron transfer pathways and molecular recognition in photosynthesis.
Area of Science:
- Plant molecular biology
- Photosynthesis research
- Protein-protein interactions
Background:
- Plastocyanin and cytochrome bf complex are key components in the photosynthetic electron transport chain.
- Understanding their interaction is crucial for elucidating energy conversion mechanisms in plants.
Purpose of the Study:
- To investigate the electron transfer site and docking regions of plastocyanin interacting with the cytochrome bf complex.
- To clarify the role of specific residues and surface patches in plastocyanin-cytochrome bf complex binding.
Main Methods:
- Stopped-flow kinetics using spinach plastocyanin mutants.
- Site-directed mutagenesis of plastocyanin, including Tyr-83, acidic residues, Ala-90, and Gly-10.
Main Results:
- Mutations at Tyr-83 did not support a secondary electron transfer pathway.
- Conserved negative patches on plastocyanin are essential for binding to the cytochrome bf complex.
- Modifications at the hydrophobic surface (Ala-90 and Gly-10) differentially affected electron transfer rates, indicating distinct binding contributions.
Conclusions:
- Plastocyanin binding to the cytochrome bf complex involves specific conserved negative patches and a divided hydrophobic region.
- The binding sites for the cytochrome bf complex are distinct from those interacting with photosystem I.
- Molecular recognition involves differential use of binding site sub-regions for different membrane complexes.