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Constitutively Active Mutants of the Histamine H1 Receptor Suggest a Conserved Hydrophobic Asparagine-Cage That Constrains the Activation of Class A G Protein-Coupled Receptors
Ist Teil von
Molecular pharmacology, 2008-01, Vol.73 (1), p.94
Ort / Verlag
United States: American Society for Pharmacology and Experimental Therapeutics
Erscheinungsjahr
2008
Quelle
Free E-Journal (出版社公開部分のみ)
Beschreibungen/Notizen
The aim of this study was to create and characterize constitutively active mutant (CAM) histamine H 1 receptors (H 1 R) using random mutagenesis methods to further investigate the activation process of the rhodopsin-like family of G protein-coupled
receptors (GPCRs). This approach identified position 6.40 in TM 6 as a âhot spotâ because mutation of Ile6.40 420 either to Glu, Gly, Ala, Arg, Lys, or Ser resulted in highly active CAM H 1 Rs, for which almost no histamine-induced receptor activation response could be detected. The highly conserved hydrophobic
amino acid at position 6.40 defines, in a computational model of the H 1 R, the asparagine cage motif that restrains the side chain of Asn7.49 of the NPxxY motif toward transmembrane domain (TM 6)
in the inactive state of the receptor. Mutation of the asparagine cage into Ala or Gly, removing the interfering bulky constraints,
increases the constitutive activity of the receptor. The fact that the Ile6.40 420 Arg/Lys/Glu mutant receptors are highly active CAM H 1 Rs leads us to suggest that a positively charged residue, presumably the highly conserved Arg3.50 from the DRY motif, interacts
in a direct or an indirect (through other side chains or/and internal water molecules) manner with the acidic Asp2.50··Asn7.49
pair for receptor activation.