Lysine 270 in the Third Intracellular Domain of the Oxytocin Receptor is an Important Determinant for Gαq Coupling Specificity

摘要: To identify structural elements important to specific Gq coupling in the oxytocin receptor (OTR), intracellular domains were exchanged between OTR and Gs-coupled vasopressin V2 receptors (V2Rs). Substitution of sequence from second (2i) third (3i) V2R into comparable positions markedly reduced ligand affinity resulted a loss coupling. 2i domain decreased vasopressin-stimulated adenylyl cyclase activity only slightly increased phosphatidylinositide turnover. In contrast, substitution OTR3i produced chimera with high affinity, activity, enhanced ligandstimulated The Cterminal 36 amino acids, but not N-terminal 13 contained determinants critical for activation PLC. Mutation single lysine C-terminal corresponding residue (valine) eliminated ability stimulate PLC did affect maximal stimulation. Furthermore, mutation this (K270) wild-type completely abolished turnover, small reduction affinity. These data demonstrate that K270 is critically stimulation by turnover determinant can also increase chimera. adversely affects ERK1/2 phosphorylation. Therefore, plays an role specificity OTR/Gq/PLC (Molecular Endocrinology 16: 814–823, 2002)