Fluorescence quenching studies of the rat ovarian LH/hCG receptor

Fluorescence quenching method providing information about the structure and dynamics of proteins, ligand-protein and protein-lipid interactions was used in a study of the rat ovarian LH/hCG receptor. The efficiency of two different quenchers, acrylamide and iodide, was tested. Acrylamide was significantly more effective in quenching of intrinsic fluorescence of ovarian membranes than iodide and therefore it was used in all of the following experiments. Both acrylamide and iodide were not effective in quenching of membranes labelled with fluorescence probe 1,6-diphenyl-1,3,5-hexatriene (DPH). In the process of desensitization of ovarian LH/hCG receptors the administration to rats of hCG modified the quenching rate of protein fluorescence and intrinsic fluorescence spectral properties of membranes. Alteration in the quenching of intrinsic fluorescence of ovarian membranes was observed after chemical modification of LH/hCG receptors by 2-hydroxy-5-nitrobenzyl bromide (HNB-Br). The accessibility of tryptophan fluorophores was increased in HNB-Br-treated membranes. Delipidation of the LH/hCG receptor modified the quenching of protein fluorescence characteristic for control proteoliposomes. These results demonstrate that fluorescence quenching technique can be successfully applied in the study of the LH/hCG receptor.