The retinal structure of channelrhodopsin-2 assessed by resonance Raman spectroscopy.
Channelrhodopsin-2 mediates phototaxis in green algae by acting as a light-gated cation channel. As a result of this property, it is used as a novel optogenetic tool in neurophysiological applications. Structural information is still scant and we present here the first resonance Raman spectra of channelrhodopsin-2. Spectra of detergent solubilized and lipid-reconstituted protein were recorded under pre-resonant conditions to exclusively probe retinal in its electronic ground state. All-trans retinal was identified to be the favoured configuration of the chromophore but significant contributions of 13-cis were detected. Pre-illumination hardly changed the isomeric composition but small amounts of presumably 9-cis retinal were found in the light-adapted state. Spectral analysis suggested that the Schiff base proton is strongly hydrogen-bonded to a nearby water molecule.
Bielefeld University, Biophysical Chemistry, 33615 Bielefeld, Germany.
Melanie
M
Nack
Ionela
I
Radu
Christian
C
Bamann
Ernst
E
Bamberg
Joachim
J
Heberle
D020418:Algal Proteins / Q000737:chemistry / Q000302:isolation & purification; D019843:Archaeal Proteins / Q000737:chemistry / Q000302:isolation & purification; D001426:Bacterial Proteins / Q000737:chemistry / Q000302:isolation & purification; D001436:Bacteriorhodopsins / Q000737:chemistry / Q000302:isolation & purification; D002352:Carrier Proteins / Q000737:chemistry*; D016825:Chlamydomonas reinhardtii / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D019617:Halobacterium salinarum / Q000737:chemistry; D008027:Light; D019633:Natronobacterium / Q000737:chemistry; D020560:Proteobacteria / Q000737:chemistry; D025604:Rhodopsins, Microbial / Q000737:chemistry* / Q000302:isolation & purification; D013059:Spectrum Analysis, Raman / Q000379:methods*; D013237:Stereoisomerism
D020418:Algal Proteins; D019843:Archaeal Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D025604:Rhodopsins, Microbial; C523009:channelopsin-2, Chlamydomonas reinhardtii; D001436:Bacteriorhodopsins