Specificity of receptor-G protein interactions. Discrimination of Gi subtypes by the D2 dopamine receptor in a reconstituted system.

摘要: The selectivity of D2 dopamine receptor-guanine nucleotide-binding protein (G protein) coupling was studied by reconstitution techniques utilizing purified receptors from bovine anterior pituitary and resolved G proteins brain, pituitary, human erythrocyte. Titration a fixed receptor concentration with varying concentrations revealed two aspects receptor-G coupling. First, Gi2 appeared to couple selectively the approximately 10-fold higher affinity than any other tested Gi subtype. Second, differed in maximal receptor-mediated agonist stimulation intrinsic GTPase activity. be maximally stimulated agonist-receptor complex turnover numbers 2 min-1. subtypes, Gi1 Gi3, could only partially activated, resulting rates 1 Agonist-stimulated activity not detected preparations containing Go brain. differences agonist-stimulated observed among subtypes explained agonist-promoted guanyl nucleotide exchange. Both guanosine 5'-3-O-(thio)triphosphate (GTP gamma S) binding GDP release parameters were enhanced 2-fold for subtype over subtypes. These results suggest that even though several types pertussis toxin substrate may exist most tissues, interact discretely proteins, thereby dictating signal transduction mechanisms.