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Side-chain interactions in the plastocyanin-cytochrome f complex
M Ejdebäck1, A Bergkvist, B G Karlsson
1Biochemistry and Biophysics, Department of Chemistry, Göteborg University, P.O. Box 462, SE-405 30 Göteborg, Sweden.
Biochemistry
|May 23, 2000
Summary
Nuclear magnetic resonance (NMR) chemical shift mapping reveals the binding interface between cytochrome f and plastocyanin. This study identifies key protein regions involved in electron transfer complex formation and specificity.
Area of Science:
- Biochemistry
- Structural Biology
- Photosynthesis Research
Background:
- Cytochrome f and plastocyanin are crucial redox partners in photosynthetic electron transfer.
- Their interaction forms a transient complex essential for efficient electron transport.
- Understanding this binding interface is key to elucidating electron transfer mechanisms.
Purpose of the Study:
- To precisely map the binding interface between cytochrome f and plastocyanin.
- To investigate the structural effects of complex formation on plastocyanin.
- To correlate structural findings with the mechanism of electron transfer.
Main Methods:
- Utilized Nuclear Magnetic Resonance (NMR) chemical shift perturbation mapping.
- Measured proton chemical shifts of plastocyanin upon titration with cytochrome f.
- Analyzed changes in approximately 500 proton resonances to identify interface regions.
Main Results:
- 86% of plastocyanin proton resonances were observable.
- 19% of resonances showed significant chemical-shift changes, localized to hydrophobic and acidic patches.
- Largest shifts occurred around His87, indicating tight hydrophobic interactions and potential water exclusion.
Conclusions:
- Both hydrophobic and acidic patches of plastocyanin are integral to the binding interface.
- His87 is critical for electron transfer and hydrophobic interactions, dictating binding specificity.
- Electrostatic interactions involving acidic patches likely contribute but allow solvent exposure.