Fig. 5. (A) The direct comparison of G-protein-anchor FRET pairs suggests that G_q and G_i/o share the same microdomain, whereas G_i/o and G_q do not. The E_max values are given in % ± s.d.; n, number of independent experiments. E_max values of heterotrimer construct FRET pairs are not significantly different (dark grey), whereas the values of G construct FRET pairs N_i2-mCFP/N_i2-mCit and N_GAP-43-mCFP/N_i2-mCit (light grey) are significantly different (P<0.05, 2-tailed Student's t-test). Blue and yellow column headings highlight mCFP- and mCit-labeled constructs, respectively. (B) The FRET map of heterotrimeric G-protein microdomains based on the results of their membrane anchors. This scheme is based on the E_max relationships, where a high E_max value relates to a large overlap of the microdomains or a higher probability of the respective molecules to co-cluster. As an example, the arrow shows how the G_i/o subunit displaces after activation. Its starting microdomain has a lesser `proximity' to the tR-microdomain-marker (low FRET), than the destination microdomain of active G_i/o (high FRET). Thus, activation results in an increase of FRET for the FRET pair G_i/o-construct/tR (Fig. 6C).