A three-dimensional movie of structural changes in bacteriorhodopsin
Eriko Nango1,2, Antoine Royant3,4, Minoru Kubo1,5
1RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan.
Science (New York, N.Y.)
|December 24, 2016
Summary
Bacteriorhodopsin, a proton pump, undergoes structural changes after light activation. These movements, visualized using advanced X-ray crystallography, reveal how it transports protons across membranes.
Area of Science:
- Membrane biophysics
- Structural biology
- Protein dynamics
Background:
- Bacteriorhodopsin (bR) functions as a light-driven proton pump.
- It serves as a model for membrane transport proteins.
- Understanding bR's mechanism is key to membrane protein function.
Purpose of the Study:
- To visualize the conformational changes in bacteriorhodopsin after photoactivation.
- To elucidate the structural dynamics of proton transport in bR.
- To map the sequence of events from nanoseconds to milliseconds.
Main Methods:
- Time-resolved serial femtosecond crystallography.
- Utilized an X-ray free electron laser (XFEL).
- Captured structural snapshots at high temporal resolution.
Main Results:
- Photoactivation causes the retinal chromophore to twist.
- This twisting displaces a tryptophan residue and a water molecule.
- A cascade of structural changes was observed throughout the protein.
Conclusions:
- The study reveals the choreographed motions underlying proton transport in bR.
- Structural changes facilitate uphill proton translocation against a gradient.
- Provides atomic-level insight into a fundamental biological process.
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