Gβ subunits from animals are anchored to membranes via Gγ subunits. No Gγ has been identified in plants to date. Using differential centrifugation of Arabidopsis and broccoli extracts, Gβ was highly enriched in the microsomal pellet. Treatment of microsomes with detergents and salts indicates that plant Gβ is located at the membrane surface and attached to membranes by hydrophobic interactions. Analysis of transgenic plants expressing Gβ–GFP fusion proteins showed that mutations in the heptad repeat domain of Gβ severely diminished their membrane association. We propose that plant Gβ is anchored to membranes by an unknown protein similar to animal Gβ by Gγ, via coiled-coil formation.
