A Gly/Ala switch contributes to high affinity binding of benzoxazinone-based non-peptide oxytocin receptor antagonists

• Published in: FEBS letters Vol. 579; no. 2; pp. 349 - 356
• Main Authors: Hawtin, Stuart R., Ha, Sookhee N., Pettibone, Douglas J., Wheatley, Mark
• Format: Journal Article
• Language: English
• Published: England Elsevier B.V 17-01-2005
• Subjects: 1-((7,7-dimethyl-2(S)-(2(S)-amino-4-(methylsulfonyl)butyramido)bicyclo[2.2.1]-heptan-1(S)-yl)methyl)sulfonyl-4-(2-methylphenyl)piperazine; 1-(1-{4-[1-(2-methyl-1-oxidopyridin-3-ylmethyl)piperidin-4-yloxyl]-2-methoxybenzoyl}piperidin-4-yl)-1,4-dihydrobenz[d][1,3]oxazin-2-one; 1-{1-[4-[(N-acetyl-4-piperidinyl)oxy]-2-methoxybenzoyl]piperidin-4-yl}-4H-3,1-benzoxazin-2(1H)-one; [arginine8]vasopressin; Alanine - genetics; Amino Acid Sequence; Amino Acid Substitution - genetics; Antidiuretic Hormone Receptor Antagonists; AVP; Benzoxazines; Binding, Competitive; bovine rhodopsin; bRho; cyclo(l-prolyl-d-2-naphthylalanyl-l-isoleucyl-d-pipecolyl-l-pipecolyl-d-histidyl); d(CH2)5Tyr(Me)2Thr4Orn8Tyr(NH2)9 vasotocin; G-protein-coupled receptor; Glycine - genetics; GPCR; human; Humans; inositol phosphate; inositol trisphosphate; InsP; InsP3; L-366,948; L-368,899; L-371,257; L-372,662; Ligand binding; Ligands; Models, Molecular; Molecular Sequence Data; Non-peptide antagonist; OTA; OTR; Oxazines - chemistry; Oxazines - pharmacology; oxytocin; Oxytocin receptor; Piperidines - chemistry; Piperidines - pharmacology; Point Mutation - genetics; Pyridines - chemistry; Pyridines - pharmacology; rat; Receptors, Oxytocin - antagonists & inhibitors; Receptors, Oxytocin - chemistry; Receptors, Oxytocin - genetics; Receptors, Vasopressin - genetics; Structure-Activity Relationship; transmembrane helix; V1a vasopressin receptor; V1aR; L-372,662; InsP; Ligand binding; Oxytocin receptor; Non-peptide antagonist; OT; h; InsP3; V1aR; OTR; L-371,257; r; L-368,899; L-366,948; GPCR; TM; bRho; AVP; OTA
• ISSN: 0014-5793; 1873-3468
• DOI: 10.1016/j.febslet.2004.10.108

Non-peptide antagonists of the oxytocin receptor (OTR) have been developed to prevent pre-term labour. The benzoxazinone-based antagonists L-371,257 and L-372,662 display pronounced species-dependent pharmacology with respect to selectivity for the OTR over the V1a vasopressin receptor. Examination of receptor sequences from different species identified Ala318 in helix 7 of the human OTR as a candidate discriminator required for high affinity binding. The mutant receptor [A318G]OTR was engineered and characterised using ligands representing many different chemical classes. Of all the ligands investigated, only the benzoxazinone-based antagonists had decreased affinity for [A318G]OTR. Molecular modelling revealed that Ala318 provides a direct hydrophobic contact with a methoxy group of L-371,257 and L-372,662.