SITE-DIRECTED MUTAGENESIS OF THE HUMAN 5-HT1B RECEPTOR

Site-directed mutagenesis was used to investigate the molecular intera ctions involved in ligand binding to the human 5-MT1B receptor. Six mu tants were constructed at four positions and expressed in Chinese hams ter ovary cells. Substitution of the amino acid F185 in transmembrane region IV by an alanine increased the affinities of sumatriptan, methy sergide and 8-hydroxy-2-(dipropylamino)tetralin (8-OH-DPAT) 3-4-fold a nd substitution by a methionine increased the affinities of methysergi de and methiothepin 2- and 3-fold, respectively. Substitution of amino acid S334 in transmembrane region VI by an alanine increased the affi nity of 8-OH-DPAT 5-fold. In accordance with this, the EC50 value of 8 -OH-DPAT was decreased 7-fold. This suggests that the serine at positi on 334 causes steric hindrance for 8-OH-DPAT binding that is lost in t he S334A mutant. Mutation of F354 in transmembrane region VII, which d iffers between receptor subtypes, increased the affinity of methiothep in 2-3-fold but the affinities of the other compounds tested were esse ntially unchanged. (C) 1998 Elsevier Science B.V. All rights reserved.