[Multicomponent system of specific estrogen-binding liver proteins. Some properties of a rapidly dissociating estrogen-binding liver protein from guinea pigs].

A study was made of some binding and physico-chemical properties of a special estrogen-binding protein of liver cytozol in sexually mature female and male guinea pigs following its partial purification by means of ammonium sulfate sedimentation, gelfiltration and ion-exchange chromatography. The given protein proved to bind estradiol (E2) with Ka of the 10(7) M-1 order and possessed a rather marked hormonal affinity specificity. Under unbalanced conditions its complexes with E2 were capable of rapid dissociation. Characteristics of the size of protein molecules were: molecular weight--about 60000, Stokes' radius--3.2 nm, sedimentation coefficient--4.6, friction coefficient ratio--1.18. Protein E2-binding activity was reversibly depressed in the presence of high salt concentrations, decreased in the presence of dithioerythritol and on heating at the temperature of over 50 degree C. The optimum E2 binding was observed at pH 7.3--7.7. There were no significant differences in the properties of protein from the liver of males and females. A conclusion was drawn on a close similarity between the given protein of guinea pigs and of a special estrogen-binding protein of the liver in male rats detected by the authors earlier.