Ligand-induced self-association of human luteinizing hormone. Negative cooperativity in the binding of 8-anilino-1-naphthalensulfonate.
The self-association of human luteinizing hormone (hLH) is enhanced in the presence of 8-anilino-1-naphthalenesulfonate (ANS). Sedimentation equilibrium measurements indicate that the hormone exists primarily as a dimer in the presence of excess ANS. It is shown that, for a self-associating protein system in which monomer and dimer have different affinities and/or capacities for ligand, both the shape and the position of the binding curve depend on protein concentration. Gel filtration and fluorescence measurements indicate that the hLH dimer has a single high affintiy site (K greater than 10(6) M-1) for ANS while binding to the monomer is too weak to be observed. This leads to negative cooperativity in the binding and to a shift of the binding curve to lower free ligand concentration with increasing concentration of the hormone.
D000817:Anilino Naphthalenesulfonates / Q000378:metabolism*; D001665:Binding Sites; D002850:Chromatography, Gel; D005260:Female; D006801:Humans; D008024:Ligands; D007986:Luteinizing Hormone / Q000378:metabolism*; D046911:Macromolecular Substances; D008956:Models, Chemical; D011485:Protein Binding; D013050:Spectrometry, Fluorescence; D013329:Structure-Activity Relationship; D014461:Ultracentrifugation
D000817:Anilino Naphthalenesulfonates; D008024:Ligands; D046911:Macromolecular Substances; D007986:Luteinizing Hormone