Purification and In Vitro Functional Analysis of the Arabidopsis thaliana Regulator of G-Protein Signaling-1

The model organism Arabidopsis thaliana contains a restricted set of heterotrimeric G-protein subunits, with only one canonical Gα subunit (AtGPA1), one Gβ subunit (AtAGB1), and two Gγ subunits (AtAGG1 and AtGG2) identified. We have identified a novel additional component of heterotrimeric G-protein signaling in the A. thaliana genome, regulator of G-protein signaling-1 (AtRGS1). This protein has the predicted topology and structure of a G-protein-coupled receptor in that it contains seven transmembrane domains, but AtRGS1 also contains a unique C-terminal extension, namely a regulator of G-protein signaling domain (RGS box). This article describes methods for the purification and in vitro functional analysis of the RGS box of AtRGS1.