Impact of Aromatic Residues within Transmembrane Helix 6 of the Human Gonadotropin-Releasing Hormone Receptor upon Agonist and Antagonist Binding

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• 作者：Sascha Hö ; velmann ; Silke H. Hoffmann ; Ronald K&uuml ; hne ; Ton ter Laak ; Helmut Reilä ; nder ; and Thomas Beckers
• 刊名：Biochemistry
• 出版年：2002
• 出版时间：January 29, 2002
• 年：2002
• 卷：41
• 期：4
• 页码：1129 - 1136
• 全文大小：263K
• 年卷期：v.41,no.4(January 29, 2002)
• ISSN：1520-4995

文摘

To investigate the impact of aromatic residues within transmembrane helix 6 (TMH6) of thehuman gonadotropin-releasing hormone receptor (GnRH-R) on agonist and antagonist binding, residuesY²⁸³, Y²⁸⁴, W²⁸⁹, Y²⁹⁰, W²⁹¹, and F²⁹² were exchanged to alanine and analyzed comprehensively in functionalreporter gene and ligand binding assays. Whereas receptor mutants Y²⁸³A, Y²⁸⁴A, and W²⁹¹A were capableof neither ligand binding nor signal transduction, mutants W²⁸⁹A, Y²⁹⁰A, and F²⁹²A were functional: theF²⁹²A mutant behaved like wild-type receptor, while mutants W²⁸⁹A and Y²⁹⁰A differentiated betweenagonistic and antagonistic ligands. On the basis of the high-resolution X-ray structure of bovine rhodopsinas well as available data on GnRH-R mutants, models for ligand-receptor interactions are proposed. Themodel for D-Trp⁶-GnRH (Triptorelin) binding, representing a superagonistic ligand, is in full accordanceto available data. Furthermore, new interactions are proposed: pGlu¹ interacts with N²¹² in transmembranehelix 5, Tyr⁵ with Y²⁹⁰, and D-Trp⁶ with W²⁸⁹. The binding behavior of mutants W²⁸⁹A and Y²⁹⁰Acorresponds to the proposed binding model for the antagonist Cetrorelix. In summary, our data as presentedindicate that Y²⁹⁰ plays a key function in agonist but not antagonist binding.