Asn 102 of the Gonadotropin-releasing Hormone Receptor Is a Critical Determinant of Potency for Agonists Containing C-terminal Glycinamide

Davidson, James S; McArdle, Craig A; Davies, Peter; Elario, Ricardo; Flanagan, Colleen A; Millar, Robert P

Asn 102 of the Gonadotropin-releasing Hormone Receptor Is a Critical Determinant of Potency for Agonists Containing C-terminal Glycinamide

Journal Article

1996

Journal Title

The Journal of Biological Chemistry

Link to Journal

https://dx.doi.org/10.1074/jbc.271.26.15510

Department

Division of Chemical Pathology

Faculty

Faculty of Health Sciences

Abstract

We demonstrate a critical role for Asn102 of the human gonadotropin-releasing hormone (GnRH) receptor in the binding of GnRH. Mutation of Asn102, located at the top of the second transmembrane helix, to Ala resulted in a 225-fold loss of potency for GnRH. Eight GnRH analogs, all containing glycinamide C termini like GnRH, showed similar losses of potency between 95- and 750-fold for the [Ala102]GnRHR, compared with wild-type receptor. In contrast, four GnRH analogs that had ethylamide in place of the C-terminal glycinamide residue, showed much smaller decreases in potency between 2.4- and 11-fold. In comparisons of three agonist pairs, differing only at the C terminus, glycinamide derivatives showed an 11-20-fold greater loss of potency for the mutant receptor than their respective ethylamide derivatives. Thus Asn102 is a critical determinant of potency specifically for ligands with C-terminal glycinamide, while ligands with C-terminal ethylamide are less dependent on Asn102. These findings indicate a role for Asn102 in the docking of the glycinamide C terminus and are consistent with hydrogen bonding of the Asn102 side chain with the C-terminal amide moiety. Taken with previous data, they suggest a region of the GnRH receptor formed by the top of helices 2 and 7 as a binding pocket for the C-terminal part of the ligand.