Allosteric and Orthosteric Binding Modes of Two Nonpeptide Human Gonadotropin-Releasing Hormone Receptor Antagonists

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• 作者：Susan K. Sullivan ; Michael S. Brown ; Yinghong Gao ; Colin J. Loweth ; Francisco M. Lio ; Paul D. Crowe ; R. Scott Struthers ; Stephen F. Betz
• 刊名：Biochemistry
• 出版年：2006
• 出版时间：December 26, 2006
• 年：2006
• 卷：45
• 期：51
• 页码：15327 - 15337
• 全文大小：374K
• 年卷期：v.45,no.51(December 26, 2006)
• ISSN：1520-4995

文摘

Nonpeptide antagonists of the human gonadotropin-releasing hormone receptor (GnRH-R)have been the subject of considerable interest because of their potential as a new class of oral therapeuticsfor the treatment of sex hormone-dependent diseases and infertility. While many classes of competitiveGnRH-R antagonists have been described, we present here the first characterization of an allostericnonpeptide GnRH-R antagonist. Previously, 5-(3,5,5,8,8-pentamethyl-5,6,7,8-tetrahydronaphthalen-2-ylmethyl)furan-2-carboxylic acid (2,4,6-trimethoxyphenyl)amide (here called Furan-1) had been demonstrated to be a potent GnRH-R antagonist both in vitro and in vivo. Using mutagenesis, the binding sitesfor Furan-1 and another potent nonpeptide antagonist (NBI-42902) have been mapped and are shown tobe adjacent but nonoverlapping. Furan-1 is shown to affect the binding kinetics of radiolabeled peptideagonists as well as radiolabeled NBI-42902, and the kinetic data fit the allosteric ternary complex model.Furan-1 is considerably negatively cooperative with the nonpeptide antagonist and extremely negativelycooperative with the peptide agonist [¹²⁵I-His5,D-Tyr6]GnRH so that it is nearly indistinguishable froman orthosteric competitive compound. Taken together, these data were used to develop a model of thenonpeptides bound to the GnRH-R binding site consistent with the current data.