Photoinduced isomerization sampling of retinal in bacteriorhodopsin
1Department of Chemistry, University of Illinois at Chicago, Chicago, IL 60607, USA.
PNAS Nexus
|August 15, 2022
Summary
Bacteriorhodopsin
Area of Science:
- Biophysics
- Structural Biology
- Photochemistry
Background:
- Retinoid photoisomerization is crucial for biological processes like vision and light sensing.
- Bacteriorhodopsin's light-driven proton pumping involves complex conformational changes.
- Resolving transient intermediates in protein photocyles is challenging due to noisy data.
Purpose of the Study:
- To identify and characterize early photoproducts in bacteriorhodopsin's photocycle.
- To elucidate the molecular events preceding and following retinal photoisomerization.
- To develop a method for resolving concurrent events from mixed time-resolved data.
Main Methods:
- Time-resolved serial crystallography.
- Numerical deconvolution of mixed intermediate populations.
- Analysis of electron density maps at atomic resolution.
Main Results:
- Several distinct early photoproducts were identified through deconvolution.
- All-trans retinal samples various isomerization pathways before forming the 13-cis configuration.
- Photoisomerization induces outward bending of transmembrane helices, expanding the binding pocket.
Conclusions:
- The productive photoreaction in bacteriorhodopsin is initiated by light-induced charge separation.
- Protein pocket stereoselectivity governs the photoisomerization process.
- The numerical deconvolution method is broadly applicable to complex biological systems.
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