co-immunoprecipitation of the Arabidopsis G protein β subunit AGB1

Heterotrimeric guanine nucleotide-binding (G) proteins are composed of Gα, Gβ, and Gγ subunits, and function as molecular switches in signal transduction. In Arabidopsis thaliana there are one canonical Gα (GPA1), three extra-large Gα (XLG1, XLG2 and XLG3), one Gβ (AGB1) and three Gγ (AGG1, AGG2 and AGG3) subunits. To elucidate AGB1 molecular signaling, we performed immunoprecipitation using plasma membrane enriched proteins followed by mass spectrometry to identify the protein interactors of AGB1. After eliminating proteins present in the control immunoprecipitation, commonly identified contaminants, and organellar proteins, a total of 103 candidate AGB1-associated proteins were confidently identified. We identified all of the G protein subunits except XLG1, receptor-like kinases (RLKs), Ca2+ signaling related proteins and 14-3-3-like proteins, all of which may couple with or modulate G protein signaling.