Testicular membranes with improved stability of the gonadotropin receptor |
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Authors: | Thomas D Noland David Puett |
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Institution: | Department of Biochemistry, Vanderbilt University, Nashville, TN 37232, U.S.A. |
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Abstract: | A plasma membrane fraction has been prepared from rat testis using an aqueous double-phase polymer system containing dextran, poly(ethylene glycol) 6000 and Zn2+. The membrane-associated gonadotropin receptor for lutropin and human choriogonadotropin can be markedly stabilized by a thawing-washing step of frozen membranes which prolongs the apparent half-life of the unoccupied membrane-associated receptors from less than 1 h at 37°C to greater than 5 h. Also, no degradation of 125I-labeled human choriogonadotropin was detected following incubation with the membrane fraction. The equilibrium binding was characterized by an apparent association constant of 1.6 · 1010 M?1 and a receptor content of 33 fmol/mg protein. Binding kinetic yielded an association rate constant of 1.0 · 108 M?1, while the dissociation rate constant for human choriogonadotropin was too low to be accurately determined under the conditions used. In contrast, ovine lutropin could be reversibly bound to the membranes leaving the previously occupied receptors available for binding by 125I-labeled human choriogonadotropin. |
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Keywords: | Receptor stability Gonadotropin (Testis membrane) CG choriogonotropin LH lutropin SDS sodium dodecyl sulfate |
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