Diethylpyrocarbonate, a Histidine Selective Reagent, Causes Structural Alteration of Rat Ovarian LH/hCG Receptor

Abstract. Treatment of íat ovanan membiane-bound and Tnton X-100 solubilized LH/hCG íeceptoi with a histidme-specific icagent diethylpyiocaibonate (DEPC) íesulted m macti\ation of the ability of the íeccptoi to bind hCG The paitial íe-veisibihťv of this inhibition by hydioxylamme domonstiated that histidine losidues aie involved m hCG-ieceptoi binding Fhioies(ence quenching expeiiments nidi cated that DEPC did not change the accessibihty of fiuoiophoies foi aciylamide Alterations of quenchiiig íate goneially suggest exposuie of tivptophanvl íesidues Modification of histidjl íesidues was connected with an alteiation of the physical state of ovanan membianes Membiane lipid iigicht\ was dec leased aftei DEPC íe action Theimal peitmbation techniques won used to monitoi stnutuial (lianges m the ícceptoi clue to the action of DEPC on membianes Heat mactnation of hCG-bmdmg sites demonstiated that theie was a signmc ant destabilization of the LH/hCG íeeeptoi stmctuie when the inembianes weio tieated with DEPC Thei mal dcstabih/ation pioduced h\ 5 mmol/1 DEPC ( ausc d a dec lease m T^, 0 \ allies bv about 12°C These íesults suggest that histidine lesidues aie lo< ated at the binding sites of the íeeeptoi and that they aie also imohed m alteiations of membiane piotems the stiuctuial mtcgiitv of w Inch sec ondanly influences the ae ce^ssibihty oi the LH/hCG íeceptoi Key words: Diethv lpyiocaibonate LH/hCG nceptois Theimal mat tnation Fluoiesc enc e polaii/atio