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pH-induced conformational changes in spinach ferredoxin: steady-state and time-resolved fluorescence studies
J Kieleczawa1, L L France, J C Sutherland
1Biology Department, Brookhaven National Laboratory, Upton, New York 11973.
Archives of Biochemistry and Biophysics
|October 1, 1992
Summary
Spinach ferredoxin undergoes significant pH-induced conformational changes, becoming more hydrophilic at higher pH. This impacts its interaction with other molecules within the chloroplast.
Area of Science:
- Biochemistry
- Plant Physiology
Background:
- Spinach ferredoxin is a crucial electron carrier in photosynthesis.
- Understanding its conformational dynamics is key to elucidating its physiological roles.
Purpose of the Study:
- To investigate pH-induced conformational changes in spinach ferredoxin.
- To correlate these changes with ferredoxin's function in photosynthesis.
Main Methods:
- Steady-state and time-resolved fluorescence spectroscopy were employed.
- Tryptophan-73 (Trp-73) emission properties were analyzed.
- Interactions with quenchers (acrylamide, I-, Cs+) and a detergent (Brij-96) were assessed.
Main Results:
- Increased pH (6.0-7.6) shifted Trp-73 emission maximum, indicating decreased local hydrophobicity.
- Higher pH reduced Brij-96 binding, suggesting overall increased protein hydrophilicity.
- Fluorescence lifetimes increased with pH, consistent with conformational changes in single-tryptophan proteins.
Conclusions:
- Spinach ferredoxin exhibits significant pH-dependent conformational flexibility.
- These changes likely influence ferredoxin's interaction with ferredoxin:NADP+ oxidoreductase.
- The findings provide insights into chloroplast function under varying light conditions.