Channelrhodopsins (ChRs) are light-gated ion channels widely used for activating selected cells in large cellular networks. ChR variants with a red-shifted absorption maximum, such as the modified Volvox carteri ChR1 red-activatable channelrhodopsin ("ReaChR," λmax = 527 nm), are of particular interest because longer wavelengths allow optical excitation of cells in deeper layers of organic tissue. In all ChRs investigated so far, proton transfer reactions and hydrogen bond changes are crucial for the formation of the ion-conducting pore and the selectivity for protons versus cations, such as Na+, K+, and Ca2+ (1). By using a combination of electrophysiological measurements and UV-visible and FTIR spectroscopy, we characterized the proton transfer events in the photocycle of ReaChR and describe their relevance for its function. 1) The central gate residue Glu130 (Glu90 in Chlamydomonas reinhardtii (Cr) ChR2) (i) undergoes a hydrogen bond change in D → K transition and (ii) deprotonates in K → M transition. Its negative charge in the open state is decisive for proton selectivity. 2) The counter-ion Asp293 (Asp253 in CrChR2) receives the retinal Schiff base proton during M-state formation. Starting from M, a photocycle branching o...Continue Reading
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Determination of retinal chromophore structure in bacteriorhodopsin with resonance Raman spectroscopy
A vibrational spectral maker for probing the hydrogen-bonding status of protonated Asp and Glu residues
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Glutamate residue 90 in the predicted transmembrane domain 2 is crucial for cation flux through channelrhodopsin 2
In channelrhodopsin-2 Glu-90 is crucial for ion selectivity and is deprotonated during the photocycle.
Towards an understanding of channelrhodopsin function: simulations lead to novel insights of the channel mechanism
Characterization of a highly efficient blue-shifted channelrhodopsin from the marine alga Platymonas subcordiformis.
Resonance Raman and FTIR spectroscopic characterization of the closed and open states of channelrhodopsin-1
Retinal chromophore structure and Schiff base interactions in red-shifted channelrhodopsin-1 from Chlamydomonas augustae
Pre-gating conformational changes in the ChETA variant of channelrhodopsin-2 monitored by nanosecond IR spectroscopy
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Proton transfers in a channelrhodopsin-1 studied by Fourier transform infrared (FTIR) difference spectroscopy and site-directed mutagenesis.
Platymonas subcordiformis Channelrhodopsin-2 (PsChR2) Function: II. RELATIONSHIP OF THE PHOTOCHEMICAL REACTION CYCLE TO CHANNEL CURRENTS.
Characterization of photo-intermediates in the photo-reaction pathways of a bacteriorhodopsin Y185F mutant using in situ photo-irradiation solid-state NMR spectroscopy
Enlightening the photoactive site of channelrhodopsin-2 by DNP-enhanced solid-state NMR spectroscopy
Light-Dark Adaptation of Channelrhodopsin Involves Photoconversion between the all-trans and 13-cis Retinal Isomers
Identification of a Natural Green Light Absorbing Chloride Conducting Channelrhodopsin from Proteomonas sulcata.
Unifying photocycle model for light adaptation and temporal evolution of cation conductance in channelrhodopsin-2
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