Light-induced dynamics in photosystem I electron transfer.
Shana L Bender1, Bridgette A Barry
1School of Chemistry and Biochemistry, Georgia Institute of Technology and the Petit Institute of Bioengineering and Bioscience, Atlanta, Georgia 30332, USA.
Biophysical Journal
|July 22, 2008
Summary
Protein dynamics regulate photosynthesis. This study reveals light-induced conformational changes in photosystem I, impacting electron transfer by altering chlorophyll structure and hydrogen bonding.
Area of Science:
- Biophysics
- Photosynthesis research
- Protein dynamics
Background:
- Protein dynamics are crucial for regulating photosynthetic electron transfer.
- Detailed descriptions of coupled protein conformational changes have been lacking.
- Photosystem I in oxygenic photosynthesis oxidizes plastocyanin/cytochrome c and reduces ferredoxin.
Purpose of the Study:
- To assign chlorophyll (chl) keto vibrational bands to P(A) and P(B) in photosystem I.
- To investigate the structural changes in P(A)(+) using isotopic labeling and spectroscopy.
- To elucidate the role of protein dynamics in photosynthetic electron transfer regulation.
Main Methods:
- Utilized specific chlorophyll isotopic labeling with (13)C and (18)O(2).
- Employed reaction-induced Fourier-transform infrared spectroscopy.
- Studied the cyanobacterium Synechocystis sp. PCC 6803.
Main Results:
- Assigned chl keto vibrational bands to P(A) and P(B).
- P(A)(+) exhibited two chl keto vibrational bands (1653 and 1687 cm(-1)), while P(A) showed one (1638 cm(-1)).
- Observed spectral differences suggest protein relaxation-induced distribution in P(A)(+) hydrogen bonding.
Conclusions:
- Light-induced conformational changes occur in photosystem I.
- These changes may regulate the oxidation of soluble electron donors and other electron transfer reactions.
- Provides unique insights into the role of protein dynamics in oxygenic photosynthesis.
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