Retinal-Based Proton Pumping in the Near Infrared
Srividya Ganapathy1, Hanka Venselaar2, Que Chen3
1Leiden Institute of Chemistry, Leiden University , 2333 CC Leiden, The Netherlands.
Journal of the American Chemical Society
|January 18, 2017
Summary
Researchers developed novel retinal analogues, including MMAR, to red-shift proton pumps like proteorhodopsin. This breakthrough enables near-infrared light-driven activity, expanding optogenetics and biotechnology applications.
Area of Science:
- Biochemistry
- Molecular Biology
- Biophysics
Background:
- Proteorhodopsin (PR) and Gloeobacter rhodopsin (GR) are visible light-activated proton pumps.
- Shifting their absorption spectra beyond 700 nm is crucial for optogenetics and sensor technologies.
Purpose of the Study:
- To investigate the spectral properties and pump activity of rhodopsins using red-shifted retinal analogues and mutations.
- To achieve significant red-shifts in rhodopsin absorption spectra for novel applications.
Main Methods:
- Synthesized and tested novel retinal analogues, including 3-methylamino-16-nor-1,2,3,4-didehydroretinal (MMAR).
- Combined MMAR with rhodopsin variants, including the PR-D212N,F234S double mutant.
- Measured spectral properties and proton pump activity under visible and near-infrared light.
Main Results:
- MMAR induced significant red-shifts in all tested rhodopsin variants, extending absorbance to 850-950 nm.
- The MMAR/PR-D212N,F234S combination achieved an unprecedented 200 nm red-shift in absorbance maximum.
- MMAR-containing holoproteins demonstrated sustained proton pump activity under near-infrared (730 nm) illumination.
Conclusions:
- MMAR is a potent red-shifting analogue for retinal proteins.
- This study reports the largest red-shift ever achieved in a retinal protein.
- MMAR-based rhodopsins are the first to exhibit significant proton pump activity under near-infrared light, opening new avenues in synthetic biology and biophysics.
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