Isospectral intermediates in the photochemical reaction cycle of anion channelrhodopsin GtACR1

The most effective tested optogenetic tools available for neuronal silencing are the light-gated anion channel proteins found in the cryptophyte alga Guillardia theta (GtACRs). Molecular mechanisms of GtACRs, including the photointermediates responsible for the open channel state, are of great inter...

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Bibliographic Details
Published in:Biophysical journal 2023-10, Vol.122 (20), p.4091-4103
Main Authors: Schleissner, Pamela, Szundi, Istvan, Chen, Eefei, Li, Hai, Spudich, John L., Kliger, David S.
Format: Article
Language:English
Subjects:
Anions - metabolism
Channelrhodopsins - metabolism
Cryptophyta - metabolism
Light
Optogenetics - methods
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Summary:The most effective tested optogenetic tools available for neuronal silencing are the light-gated anion channel proteins found in the cryptophyte alga Guillardia theta (GtACRs). Molecular mechanisms of GtACRs, including the photointermediates responsible for the open channel state, are of great interest for understanding their exceptional conductance. In this study, the photoreactions of GtACR1 and its D234N, A75E, and S97E mutants were investigated using multichannel time-resolved absorption spectroscopy. For each of the proteins, the analysis showed two early microsecond transitions between K-like and L-like forms and two late millisecond recovery steps. Spectral forms associated with potential molecular intermediates of the proteins were derived and their evolutions in time were analyzed. The results indicate the presence of isospectral intermediates in the photocycles and expand the range of potential intermediates responsible for the open channel state.
ISSN:0006-3495
1542-0086
1542-0086
DOI:10.1016/j.bpj.2023.09.009