Regulator of G-protein signaling (RGS) proteins of the R7 subfamily (RGS6, 7, 9, and 11) contain a unique Gγ-like (GGL) domain that enables their association with the G-protein β subunit Gβ5. The existence of these complexes was demonstrated by their purification from native tissues as well as by reconstitution in vitro. According to pulse-chase analysis, Gβ5 and RGS7 monomers undergo rapid proteolytic degradation in cells, whereas the dimer is stable. Studies of the functional role of Gβ5-RGS dimers using GTPase activity, ion channel, and calcium mobilization assays showed that, similarly to other RGS proteins, they can negatively regulate G-protein-mediated signal transduction. Protein-protein interactions involving the Gβ5-RGS7 complex can be studied in cells using fluorescence resonance energy transfer utilizing Gβ5, RGS, and Gα subunits fused to the cyan and yellow versions of green fluorescent protein.
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