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Open AccessFeature PaperArticle

Mutated Channelrhodopsins with Increased Sodium and Calcium Permeability

Botanik I, Julius-Maximilians-Universität Würzburg, Biozentrum, Julius-von-Sachs-Platz 2, D-97082 Würzburg, Germany
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Appl. Sci. 2019, 9(4), 664; https://doi.org/10.3390/app9040664
Received: 14 January 2019 / Revised: 7 February 2019 / Accepted: 12 February 2019 / Published: 15 February 2019
(This article belongs to the Special Issue The Advances and Applications of Optogenetics)
(1) Background: After the discovery and application of Chlamydomonas reinhardtii channelrhodopsins, the optogenetic toolbox has been greatly expanded with engineered and newly discovered natural channelrhodopsins. However, channelrhodopsins of higher Ca2+ conductance or more specific ion permeability are in demand. (2) Methods: In this study, we mutated the conserved aspartate of the transmembrane helix 4 (TM4) within Chronos and PsChR and compared them with published ChR2 aspartate mutants. (3) Results: We found that the ChR2 D156H mutant (XXM) showed enhanced Na+ and Ca2+ conductance, which was not noticed before, while the D156C mutation (XXL) influenced the Na+ and Ca2+ conductance only slightly. The aspartate to histidine and cysteine mutations of Chronos and PsChR also influenced their photocurrent, ion permeability, kinetics, and light sensitivity. Most interestingly, PsChR D139H showed a much-improved photocurrent, compared to wild type, and even higher Na+ selectivity to H+ than XXM. PsChR D139H also showed a strongly enhanced Ca2+ conductance, more than two-fold that of the CatCh. (4) Conclusions: We found that mutating the aspartate of the TM4 influences the ion selectivity of channelrhodopsins. With the large photocurrent and enhanced Na+ selectivity and Ca2+ conductance, XXM and PsChR D139H are promising powerful optogenetic tools, especially for Ca2+ manipulation. View Full-Text
Keywords: optogenetics; channelrhodopsins; sodium; calcium; DC gate optogenetics; channelrhodopsins; sodium; calcium; DC gate
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Duan, X.; Nagel, G.; Gao, S. Mutated Channelrhodopsins with Increased Sodium and Calcium Permeability. Appl. Sci. 2019, 9, 664.

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