Two Putative G-Protein α Subunits Dissociate from Rice Coleoptile Membranes after GTP Stimulation

The antibody raised against an aminoacidic sequence that is conserved among many animal G protein α subunits (anti-α common antibody) recognized some membrane proteins from rice coleoptile on immunoblot. Two of them, showing apparent molecular weights of 28 and 30 kDa, dissociated from aerobic and anoxic coleoptile membranes following GTPγS or GTP stimulation, but not after GDP addition. Furthermore, anti-α common antibody could be used to immunoprecipitate a saturable GTP binding activity from the supernatant of [35S]GTPγS-stimulated membranes, but not after [3H]GDP addition.