High affinity specific binding of the thyrotrophin releasing hormone metabolite histidylproline to rat brain membranes |
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| Authors: | P J Coggins J R McDermott C R Snell |
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| Institution: | 1. CSIRO Agriculture and Food, 39 Kessels Road, Coopers Plains, Qld, Australia;2. School of Biomolecular and Physical Sciences, Griffith University, Nathan, Qld, Australia;3. Departamento de Tecnologia de los Alimentos, Facultad de Ciencias Veterinarias, Universidad Nacional Del Centro de La Província de Buenos Aires, Tandil, Bs. As., Argentina;4. Department of Veterinary and Agricultural Science, The University of Melbourne, Parkville, Vic, Australia;1. Laboratory of Microbiology and Biotechnology of Foods, Department of Food Science and Human Nutrition, Agricultural University of Athens, Iera Odos 75, Athens 11855, Greece;2. Institute of Technology of Agricultural Products, Hellenic Agricultural Organization — DEMETER, Sof. Venizelou 1, Lycovrissi, Athens, Greece |
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| Abstract: | Histidylproline a metabolite of Thyrotrophin Releasing Hormone specifically binds to both high and low affinity sites in fresh rat brain membranes. Characterisation of the high affinity site under optimal conditions demonstrated an equilibrium dissociation constant (KD) of approximately 9nM and maximum binding capacity of approximately 120 fmols/mg protein. Kinetic analysis of 3H]-His-Pro binding is limited by low binding density, instability of the high affinity site and rapid degradation of the radioligand. The thiol blocking reagent pHydroxymercuriphenylsulphonic acid (HMPS) inhibited 3H]-His-Pro degradation but also reduced binding of the peptide to membranes. The results are discussed with reference to the lack of specific binding sites in brain for the proposed neuropeptide and TRH metabolite cyclo(His-Pro). |
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