Kinetics of Gq activation. (A) The fluorescence resonance energy transfer (FRET) ratio change (yellow fluorescent protein:monomeric Turquoise (YFP:mTq)) upon addition of histamine in cells expressing Gαq-mTqΔ6, Gβ1, YFP-Gγ2 and histamine H1 receptor (H1R), measured with high temporal resolution. Images were acquired at a frame rate of 0.064 seconds, and 1000 data points are shown. (B) Average FRET ratio change (scaled between 0 and 1) upon addition of histamine (n = 11; error bars depict SE). The data points were appropriately fitted with a monoexponential curve (solid line).