Solubilization of the Gonadotropin-Releasing Hormone Receptor From Bovine Pituitary Plasma Membranes

The plasma membrane receptor for GnRH in bovine anterior pituitaries has been solubilized with the cholic acid derivative detergent 3([3-cholamidopropyl)dimethylammonio]propane sulfonate. The soluble receptor in the supernatant from a 100,000 x g x 90 min centrifugation displays high affinity, saturability and specific binding to the agonist, [DA1a6,N alpha MeLeu7, Pro9-NEt]-GnRH. The dissociation constant, KD, for the soluble receptor is 0.56 +/- 0.07 nM (mean +/- SEM) and the number of sites, Ro, is 85 +/- 17 fmols/mg protein. For the membrane-bound receptor the KD is 0.50 +/- 0.04 nM and Ro is 300 +/- 18 fmols/mg protein. The relative potencies of GnRH and the potent antagonist, [Ac-delta 3Pro1,pFDPhe2, DTrp3,6]-GnRH are similar for both the soluble and membrane-bound receptor.