Figure 2.

Dynamic range of Gq sensors. (A) The fluorescence resonance energy transfer (FRET) ratio change (yellow fluorescent protein:monomeric Turquoise (YFP:mTq)) upon addition of histamine (100 μmol/l) in HeLa cells coexpressing Gαq-mTqΔ6, Gβ1, YFP-Gγ2 and the histamine H1 receptor (H1R) (Inset) the mTq and YFP intensity traces from which the ratio was derived (n = 14; error bars depict SE). Addition of the H1R inverse agonist mepyramine (10 μmol/l) reversed the ratio change induced by histamine. (B) The FRET ratio change (YFP:CFP) upon addition of histamine (100 μmol/l) in HeLa cells coexpressing Gαq-enhanced (E)CFP, EYFP-Gβ1, Gγ2 and H1R. (Inset) the CFP and YFP intensity traces from which the YFP:CFP ratio was derived (n = 17; error bars depict SE). (C) Representative trace of the FRET ratio change (YFP:mTq) upon addition of histamine (100 μmol/l) in HeLa cells coexpressing Gαq- mTqΔ6, EYFP-Gβ1, Gγ2 and H1R. (Inset). The mTq and YFP intensity traces from which the ratio was derived. (D) The FRET ratio change (YFP:CFP) upon addition of histamine (100 μmol/l) in HeLa cells coexpressing Gαq-ECFP, Gβ1, YFP-Gγ2 and H1R. (Inset) the CFP and YFP intensity traces from which the ratio was derived (n = 5; error bars depict SE).