RGS11 interacts preferentially with R7BP over Gαoa - Characterization of Gβ5-free RGS11

Regulator of G protein signaling 11 (RGS11) is the least characterized member of the R7 family of Gγ-like GGL domain-containing RGS proteins. All R7-RGS proteins of a variety of cell types are found in Gβ5-containing complexes that exhibit a number of unique functional properties. However, presence of Gβ5 reduced the affinity of R7-RGS7 for Gα subunits, also only RGS7 bound to Muscarinic M3-Receptor, but the Gβ5-RGS7 dimer did not, making it difficult to study differential interaction of R7-RGS proteins. Here, we report the successful purification of functionally intact, Gβ5-free recombinant RGS11 (rRGS11), obtained by expressing N- and C-terminally truncated form of RGS11 in Escherichia coli BL 21 (DE3), that differentially interact with R7BP and Gαoa. rRGS11 was capable of interacting with Gαoa and R7BP (RGS7 family binding protein) with equilibrium dissociation constants (KD) of 904 (±208) nM, and 308 (±97) nM, respectively. It also induced several-fold increase in the GTPase activity of Gαoa. The binding of rRGS11 was differential with a binding preference for R7BP over Gαoa implying extended roles of R7BP. In addition, we identified a novel interaction between Gαoa and R7BP with a KD of 592 (±150) nM. The production of stable and functional rRGS11 would provide chances to discover more functions of RGS11 yet to be identified.