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Proton Transfer and Protein Conformation Dynamics in Photosensitive Proteins by Time-resolved Step-scan Fourier-transform Infrared Spectroscopy
Published on: June 27, 2014
Structural changes in the L photointermediate of bacteriorhodopsin
Janos K Lanyi1, Brigitte Schobert
1Department of Physiology & Biophysics, University of California, Irvine, CA 92697, USA. jlanyi@orion.oac.uci.edu
Journal of Molecular Biology
|December 5, 2006
Summary
The L state structure of bacteriorhodopsin reveals a twisted 13-cis retinal. Proton transfer to Asp85 likely occurs via Wat402, clarifying the transport mechanism.
Area of Science:
- Biochemistry
- Structural Biology
- Photochemistry
Background:
- Bacteriorhodopsin's photocycle involves proton transfer crucial for its function.
- Previous crystallographic structures of the L state showed significant discrepancies.
- Understanding the L state is key to elucidating bacteriorhodopsin's transport mechanism.
Purpose of the Study:
- To resolve discrepancies in bacteriorhodopsin's L state structure.
- To provide a high-resolution structural model of the L state.
- To clarify the proton transfer pathway in the L to M transition.
Main Methods:
- X-ray diffraction at 1.53-1.73 Å resolution.
- Refinement using diffraction intensities from the same crystals before and after illumination.
- Analysis of inter-atomic distances, bond angles, and torsions of retinal.
Main Results:
- A reproducible structural model of the L state was obtained.
- The 13-cis retinal is twisted at C(13)=C(14) and C(15)=NZ double-bonds.
- The Schiff base remains connected to Wat402, suggesting a proton transfer pathway via Wat402 to Asp85.
Conclusions:
- Proton transfer from Schiff base to Asp85 in L to M reaction likely occurs via Wat402.
- Conformational changes propagate from retinal to protein in the L state.
- These changes are essential for bacteriorhodopsin's proton transport mechanism.
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