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  Atomistic Insight into the Role of Threonine 127 in the Functional Mechanism of Channelrhodopsin-2

Ehrenberg, D., Krause, N., Saita, M., Bamann, C., Kar, R. K., Hoffmann, K., et al. (2019). Atomistic Insight into the Role of Threonine 127 in the Functional Mechanism of Channelrhodopsin-2. Applied Sciences, 9(22): 4905. doi:10.3390/app9224905.

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 Creators:
Ehrenberg, David1, Author
Krause, Nils2, Author
Saita, Mattia1, Author
Bamann, Christian3, Author              
Kar, Rajiv K.4, Author
Hoffmann, Kirsten2, Author
Heinrich, Dorothea2, Author
Schapiro, Igor4, Author
Heberle, Joachim1, Author
Schlesinger, Ramona2, Author
Affiliations:
1Experimental Molecular Biophysics, Department of Physics, Freie Universität Berlin, Germany, Arnimallee 14, 14195 Berlin, Germany, ou_persistent22              
2Genetic Biophysics, Department of Physics, Freie Universität Berlin, Germany, Arnimallee 14, 14195 Berlin, Germany, ou_persistent22              
3Emeritusgruppe Biophysikalische Chemie, Max Planck Institute of Biophysics, Max Planck Society, ou_2253652              
4Fritz Haber Center for Molecular Dynamics Research, Institute of Chemistry, Hebrew University of Jerusalem, Jerusalem 9190401, Israel, ou_persistent22              

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Free keywords: channelrhodopsin; resonance Raman; flash photolysis; hybrid QM/MM simulation; electrophysiology
 Abstract: Channelrhodopsins (ChRs) belong to the unique class of light-gated ion channels. The structure of channelrhodopsin-2 from Chlamydomonas reinhardtii (CrChR2) has been resolved, but the mechanistic link between light-induced isomerization of the chromophore retinal and channel gating remains elusive. Replacements of residues C128 and D156 (DC gate) resulted in drastic effects in channel closure. T127 is localized close to the retinal Schiff base and links the DC gate to the Schiff base. The homologous residue in bacteriorhodopsin (T89) has been shown to be crucial for the visible absorption maximum and dark–light adaptation, suggesting an interaction with the retinylidene chromophore, but the replacement had little effect on photocycle kinetics and proton pumping activity. Here, we show that the T127A and T127S variants of CrChR2 leave the visible absorption maximum unaffected. We inferred from hybrid quantum mechanics/molecular mechanics (QM/MM) calculations and resonance Raman spectroscopy that the hydroxylic side chain of T127 is hydrogen-bonded to E123 and the latter is hydrogen-bonded to the retinal Schiff base. The C=N–H vibration of the Schiff base in the T127A variant was 1674 cm−1, the highest among all rhodopsins reported to date. We also found heterogeneity in the Schiff base ground state vibrational properties due to different rotamer conformations of E123. The photoreaction of T127A is characterized by a long-lived P2380 state during which the Schiff base is deprotonated. The conservative replacement of T127S hardly affected the photocycle kinetics. Thus, we inferred that the hydroxyl group at position 127 is part of the proton transfer pathway from D156 to the Schiff base during rise of the P3530 intermediate. This finding provides molecular reasons for the evolutionary conservation of the chemically homologous residues threonine, serine, and cysteine at this position in all channelrhodopsins known so far.

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Language(s): eng - English
 Dates: 2019-10-112019-09-282019-11-122019-11-15
 Publication Status: Published online
 Pages: 15
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.3390/app9224905
 Degree: -

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Title: Applied Sciences
Source Genre: Journal
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Publ. Info: Basel, Schweiz : MDPI
Pages: - Volume / Issue: 9 (22) Sequence Number: 4905 Start / End Page: - Identifier: ISSN: 2076-3417
CoNE: https://pure.mpg.de/cone/journals/resource/2076-3417