title: Equine follicle-stimulating hormone. Purification, acid dissociation, and binding to equine testicular tissue.
abstract: A simple method of purification of equine follicle-stimulating hormone is described by which two forms of the hormone are obtained. The acid dissociation of the most active preparation was studied and a pKa of 5.8 was determined at 37 degrees C. This value is 2 pH units higher than that observed for pregnant mare serum gonadotropin suggesting that the binding areas between subunits are not identical in the two hormones. We also describe an homologous radioreceptor assay of equine follicle-stimulating hormone which is highly specific for this hormone in contrast to the heterologous systems described so far. The analysis of the properties of equine gonadotropins in homologous and heterologous radioreceptor assays suggests that all glycoprotein hormones share a common high affinity binding site and that specificity of binding is due to binding prohibition sites preventing fixation of each hormone to the receptors of the other glycoprotein hormones. This specific hindering is defined as "negative specificity."
mesh_terms: D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001667:Binding, Competitive; D005640:Follicle Stimulating Hormone / Q000302:isolation & purification / Q000378:metabolism*; D006736:Horses; D007700:Kinetics; D007986:Luteinizing Hormone / Q000378:metabolism; D008297:Male; D011956:Receptors, Cell Surface / Q000378:metabolism*; D011962:Receptors, FSH; D011974:Receptors, LH; D011989:Receptors, Thyrotropin; D013329:Structure-Activity Relationship; D013737:Testis / Q000378:metabolism*; D013972:Thyrotropin / Q000378:metabolism
chemical_list: D000596:Amino Acids; D011956:Receptors, Cell Surface; D011962:Receptors, FSH; D011974:Receptors, LH; D011989:Receptors, Thyrotropin; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D013972:Thyrotropin