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. Author manuscript; available in PMC: 2018 Nov 28.
Published in final edited form as: Chemosensors (Basel). 2017 Nov 28;5(4):32. doi: 10.3390/chemosensors5040032

Figure 3. Schematic representation of genetically encoded voltage indicators.

Figure 3

(A) VSFP-butterfly1.2 is a FRET-based voltage sensor consists of mCtirine, CiVSD and mKate. Membrane depolarization induces a conformational change of CiVSD, which alters the FRET efficiency between the donor and acceptor; (B) ASAP1 is a single FP based voltage sensor made by inserting cpGFP in the S3–S4 linker of GgVSD. The conformational change of GgVSD can be transduced to cpGFP, leading to voltage dependent green fluorescence change; (C) ArcLight consists of Ci-VSD and super ecliptic pHluorin (A227D). Compared to other FP, this mutant FP has a higher sensitivity to the conformational change of CiVSD; (D) MacQ-mCitrine is a hybrid voltage reporter consisting a rhodopsin (MacQ) as FRET acceptor and a yellow fluorescent protein (mCitrine) as FRET donor. Membrane depolarization protonates the Schiff base of the bound retinal (orange star) cofactor in rhodopsin, shifting the cofactor absorption spectrum and enhancing FRET efficiency from mCitrine to the weakly fluorescent retinal cofactor.