Plant heterotrimeric G protein beta 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 cent rifugation of Arabidopsis and broccoli extracts, G beta was highly enriched in the microsomal pellet. Treatment of microsomes with detergents and salt s indicates that plant G beta is located at the membrane surface and attach ed to membranes by hydrophobic interactions. Analysis of transgenic plants expressing G beta-GFP fusion proteins showed that mutations in the heptad r epeat domain of G beta severely diminished their membrane association. We p ropose that plant G beta is anchored to membranes by an unknown protein sim ilar to animal G beta by G gamma, via coiled-coil formation. (C) 2000 Feder ation of European Biochemical Societies, Published by Elsevier Science B.V. All rights reserved.