title: Positive co-operativity in the membrane receptor mediated response.
abstract: In a hormonal system stimulated by one of the known hypothalamic peptides, gonadotropin releasing hormone (GnRH), the biological response seen, when physiologically called for, may be positively co-operative, showing as well the expected dynamics due to a singular or continuing stimulus. Mediation is by a receptor protein which in purified form shows positively co-operative binding and specifically aggregates in solution in the presence of the hypothalamic peptide. An introduced simple amplification receptor model encompassing both kinetic and structural features is based on known biological and biochemical parameters of the hormonal system. A novel feature of the model is an obligatory presence on a cell, at given times, of characteristic molecular forms (assemblies of various order) which all must be fully occupied as a condition of (1) their nontransient existence and (2) stimulus mediated effects. The model relates temporal changes in assemblies' occupancy, conformation and affinity to ligand concentration. It provides for sigmoid dose response curve.
mesh_terms: D000818:Animals; D001665:Binding Sites; D002417:Cattle; D005260:Female; D006801:Humans; D008024:Ligands; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D008954:Models, Biological; D010906:Pituitary Hormone-Releasing Hormones / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism*; D011966:Receptors, LHRH
chemical_list: D008024:Ligands; D008565:Membrane Proteins; D010906:Pituitary Hormone-Releasing Hormones; D011956:Receptors, Cell Surface; D011966:Receptors, LHRH