FIGURE 4.

BIM-46187 inhibits the physical interaction between GPCR and the heterotrimeric G protein and the GDP/GTP exchange. A, fluorescence emission spectra of the purified Alexa-488-labeled BLT1 receptor mixed with the G protein trimer Gα_i2β₁γ₂ where the Gα_i2 subunit is labeled with Alexa-568 in the presence of LTB4 (1 μm) and in the absence or presence of BIM-46187. The absence of nonspecific FRET was assessed by using Gα_sβ1γ2 instead of Gα_i2β₁γ₂. B, changes in the intensity of the 603-nm band as a function of BIM-46187 concentration (■). Open triangles (△) correspond to the changes when using Alexa-568-labeled β-arrestin 1 instead of Gα_i2β₁γ₂. C, inhibition of BLT1-catalyzed GTPγS binding on the purified Gα_i2β₁γ by increasing concentrations in BIM-46187. D, effects of BIM-46187 on GTP binding induced by the GPCR peptidomimetic Mastoparan-7. The data are the means ± S.E. of three independent experiments. E, effects of BIM-46187 on FUB132-induced GTP binding to isolated Gα_i2. The data are normalized to the maximal effect observed in the absence of BIM-46187. F, effects of BIM-46187 on AlF₄⁻-induced fluorescence changes of Gα_i2. The data are normalized to the maximal effect observed in the absence of BIM-46187. The data are the means ± S.E. of three independent experiments. DMSO, dimethyl sulfoxide.