Plant heterotrimeric G protein β subunit is associated with membranes via protein interactions involving coiled-coil formation

G beta subunits from animals are anchored to membranes via G gamma subunits. No G gamma has been identified in plants to date. Using differential centrifugation of Arabidopsis and broccoli extracts, G beta was highly enriched in the microsomal pellet. Treatment of microsomes with detergents and salts indicates that plant G beta is located at the membrane surface and attached to membranes by hydrophobic interactions. Analysis of transgenic plants expressing G beta-GFP fusion proteins showed that mutations in the heptad repeat domain of G beta severely diminished their membrane association. We propose that plant G beta is anchored to membranes by an unknown protein similar to animal G beta by G gamma, via coiled-coil formation. (C) 2000 Federation of European Biochemical Societies, Published by Elsevier Science B.V. All rights reserved.