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Open AccessArticle

Photocycle Dynamics of the Archaerhodopsin 3 Based Fluorescent Voltage Sensor QuasAr1

1
Fakultät für Physik, Universität Regensburg, Universitätsstraße 31, D-93053 Regensburg, Germany
2
Experimentelle Biophysik, Institut für Biologie, Humboldt Universität zu Berlin, Invalidenstraße 42, D-10115 Berlin, Germany
*
Author to whom correspondence should be addressed.
Int. J. Mol. Sci. 2020, 21(1), 160; https://doi.org/10.3390/ijms21010160
Received: 8 November 2019 / Revised: 18 December 2019 / Accepted: 19 December 2019 / Published: 25 December 2019
The retinal photocycle dynamics of the fluorescent voltage sensor QuasAr1 (Archaerhodopsin 3 P60S-T80S-D95H-D106H-F161V mutant from Halorubrum sodomense) in pH 8 Tris buffer was studied. The samples were photoexcited to the first absorption band of the protonated retinal Schiff base (PRSB) Ret_580 (absorption maximum at λmax ≈ 580 nm), and the retinal Schiff base photoisomerization and protonation state changes were followed by absorption spectra recordings during light exposure and after light exposure. Ret_580 turned out to be composed of two protonated retinal Schiff base isomers, namely Ret_580I and Ret_580II. Photoexcitation of Ret_580I resulted in barrier-involved isomerization to Ret_540 (quantum yield ≈ 0.056) and subsequent retinal proton release leading to Ret_410 deprotonated retinal Schiff base (RSB). In the dark, Ret_410 partially recovered to Ret_580I and partially stabilized to irreversible Ret_400 due to apoprotein restructuring (Ret_410 lifetime ≈ 2 h). Photoexcitation of Ret_580II resulted in barrier-involved isomerization to Ret_640 (quantum yield ≈ 0.00135) and subsequent deprotonation to Ret_370 (RSB). In the dark, Ret_370 partially recovered to Ret_580II and partially stabilized to irreversible Ret_350 due to apoprotein restructuring (Ret_370 lifetime ≈ 10 h). Photocycle schemes and reaction coordinate diagrams for Ret_580I and Ret_580II were developed and photocyle parameters were determined. View Full-Text
Keywords: QuasAr1; Archaerhodopsin 3; genetically encoded fluorescent voltage sensor; absorption spectroscopic characterization; fluorescence studies; photocycle dynamics; photoisomerization; deprotonation; reprotonation QuasAr1; Archaerhodopsin 3; genetically encoded fluorescent voltage sensor; absorption spectroscopic characterization; fluorescence studies; photocycle dynamics; photoisomerization; deprotonation; reprotonation
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Penzkofer, A.; Silapetere, A.; Hegemann, P. Photocycle Dynamics of the Archaerhodopsin 3 Based Fluorescent Voltage Sensor QuasAr1. Int. J. Mol. Sci. 2020, 21, 160.

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