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Welsby PJ, Carr IC, Wilkinson G, Milligan G: Regulation of the avidity of ternary complexes containing the human 5-HT (1A) receptor by mutation of a receptor contact site on the interacting G protein alpha subunit. Br J Pharmacol. 2002 Oct;137(3):345-52.
1 Fusion proteins were constructed between the human 5-HT (1A) receptor and pertussis toxin-resistant forms of both G (i1) alpha and G (o1) alpha mutated at residue (351) from cysteine to either glycine or isoleucine. Each of these was expressed stably in HEK293 cells. 2 Increasing concentrations of GDP inhibited binding of the agonist [(3) H]-8-OH-DPAT but not the antagonist [(3) H]-MPPF to each construct. 3 The IC (50) for GDP was greater for constructs containing isoleucine at residue (351) of the G proteins compared to those with glycine at this position. 4 The G protein antagonist suramin had similar effects to GDP on the binding of [(3) H]-8-OH-DPAT. 5 The proportion of 5-HT (1A) receptor binding sites detected by [(3) H]-MPPF that displayed high affinity for 8-OH-DPAT was significantly greater when the interacting G protein contained isoleucine rather than glycine at residue (351). 6 The 5-HT (1A) receptor displayed similar avidity of interaction with G (i1) alpha and G (o1) alpha. 7 These results indicate that a higher avidity ternary complex is formed between 8-OH-DPAT, the 5-HT (1A) receptor and G proteins when isoleucine rather than glycine is located at residue (351) of the interacting G protein. |
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