Evidence for G-protein-linked receptors in higher plants: stimulation of GTP-gamma-S binding to membrane fractions by the mastoparan analogue mas 7

Stimulation of G-protein activity by the amphipathic tetradecapeptide mastoparan is well documented in animal systems and occurs via mimickry of the third cytoplasmic domain of the cognate seven-transmembrane-span (7TMS) receptor. Binding of guanosine 5-O-thiotriphosphate to microsomal and plasma-membrane fractions from Pisum sativum L. and Zea mays L. was stimulated by the tetradecapeptide mastoparan analogue mas 7 over a narrow concentration range, with maximal effect exerted at 10 M peptide, while the nonamphipathic analogue, mas CP, which differed from mas 7 by only one amino acid, was ineffective at promoting binding. This stimulation could be completely abolished by inclusion of low concentrations of the non-ionic detergents nonanoyl-N-methylglucamide and Lubrol PX. Taken together, these data provide good evidence for the existence of G-protein-linked 7TMS receptors in higher plant systems.Abbreviations GTPS guanosine 5-O-thiotriphosphate - MEGA-9 nonanoyl-N-methylglucamide - 7TMS 7 trans-membrane span The authors wish to acknowledge the financial support of the European Community (I.R.W.), ICI and the Science and Engineering Research Council (A.W.) and the Agricultural and Food Research Council (P.A.M.).