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Updated: Aug 9, 2026
10:03
Proton Transfer and Protein Conformation Dynamics in Photosensitive Proteins by Time-resolved Step-scan Fourier-transform Infrared Spectroscopy
Published on: June 27, 2014
Water as a cofactor in the unidirectional light-driven proton transfer steps in bacteriorhodopsin
Akio Maeda1, Joel E Morgan, Robert B Gennis
1Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL, USA. amaeda@uiuc.edu
Photochemistry and Photobiology
|April 26, 2006
Summary
Internal water molecules play a crucial role in bacteriorhodopsin
Area of Science:
- Biophysics
- Structural Biology
- Photochemistry
Background:
- Bacteriorhodopsin is a light-driven proton pump.
- Its photocycle involves several transient intermediates.
- The role of internal water molecules in its mechanism is under investigation.
Purpose of the Study:
- To review and analyze the involvement of internal water molecules in bacteriorhodopsin's mechanism.
- To investigate the structural and functional roles of water during the photocycle.
Main Methods:
- Fourier transform infrared (FTIR) difference spectroscopy.
- Photoreactions at cryogenic temperatures.
- Analysis of water O-H stretching vibration bands in L, M, and N intermediates.
Main Results:
- A water structure connecting the Schiff base to Thr46-Asp96 was identified in the L intermediate.
- This water structure is transient and disappears in the M intermediate.
- Water interaction with the Schiff base is re-established in the N intermediate.
Conclusions:
- Internal water molecules are critical mobile components in bacteriorhodopsin.
- Organized water structures form in transient intermediates, influencing their chemical behavior.
- Water plays a significant role in the stabilization of intermediates during the photocycle.
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