Isolation of a putative receptor from Zea mays microsomal membranes that interacts with the G-protein, GP alpha 1

The C-terminal region of a heterotrimeric G-protein alpha-subunit is known to be one of the principal determinants governing its interaction with its cognate receptor. Use of an oligopeptide corresponding to the fifteen C-terminal residues of the Arabidopsis G alpha-subunit (GP alpha 1), as an affinity ligand, led to the resolution of a tightly binding 37 kDa membrane polypeptide from detergent solubilised Zea microsomal fraction membranes. An identical polypeptide bound tightly to an affinity matrix containing recombinant GP alpha 1 protein as ligand: binding and release of this 37 kDa protein was dependent on the activation state of GP alpha 1 which was regulated by inclusion or omission of the G-protein activator AlF-4. Finally, the isolated 37 kDa protein was labelled with the lectin concanavalin A, indicating it to be glycosylated. These data are consistent with the identity of the 37 kDa membrane polypeptide as a receptor that interacts with the Zea homologue of GP alpha 1.