%0 Journal Article %A Kim A. Neve %A Medhane G. Cumbay %A Kimberly R. Thompson %A Rui Yang %A David C. Buck %A Val J. Watts %A Curtiss J. DuRand %A Martha M. Teeter %T Modeling and Mutational Analysis of a Putative Sodium-Binding Pocket on the Dopamine D2 Receptor %D 2001 %R 10.1124/mol.60.2.373 %J Molecular Pharmacology %P 373-381 %V 60 %N 2 %X A homology model of the dopamine D2 receptor was constructed based on the crystal structure of rhodopsin. A putative sodium-binding pocket identified in an earlier model (PDB 1I15) was revised. It is now defined by Asn-419 backbone oxygen at the apex of a pyramid and Asp-80, Ser-121, Asn-419, and Ser-420 at each vertex of the planar base. Asn-423 stabilizes this pocket through hydrogen bonds to two of these residues. Highly conserved Asn-52 is positioned near the sodium pocket, where it hydrogen-bonds with Asp-80 and the backbone carbonyl of Ser-420. Mutation of three of these residues, Asn-52 in helix 1, Ser-121 in helix 3, and Ser-420 in helix 7, profoundly altered the properties of the receptor. Mutants in which Asn-52 was replaced with Ala or Leu or Ser-121 was replaced with Leu exhibited no detectable binding of radioligands, although receptor immunoreactivity in the membrane was similar to that in cells expressing the wild-type D2L receptor. A mutant in which Asn-52 was replaced with Gln, preserving hydrogen-bonding capability, was similar to D2L in affinity for ligands and ability to inhibit cAMP accumulation. Mutants in which either Ser-121 or Ser-420 was replaced with Ala or Asn had decreased affinity for agonists (Ser-121), but increased affinity for the antagonists haloperidol and clozapine. Interestingly, the affinity of these Ser-121 and Ser-420 mutants for substituted benzamide antagonists showed little or no dependence on sodium, consistent with our hypothesis that Ser-121 and Ser-420 contribute to the formation of a sodium-binding pocket. %U https://molpharm.aspetjournals.org/content/molpharm/60/2/373.full.pdf