An attempt to isolate an oestradiol receptor from nuclei by adsorption on oestradiol-17-beta.

Abstract

SUMMARY The binding of nuclear proteins from dimethylbenzanthracene (DMBA)-induced rat mammary tumours and other natural and synthetic proteins to columns of oestradiol-17β (oestradiol) has been studied. A wide range of proteins, but not DNA, bind to oestradiol under these conditions and this binding is disrupted by acid. Both histone and acidic nuclear protein fractions bind to oestradiol and the bound fraction had, in both cases, the ability to bind [6,7-3H]oestradiol. Acrylamide gel electrophoresis showed that more than one protein from both the acidic and basic nuclear protein fractions was bound to the oestradiol. More poly-l-glutamic acid and poly-l-glycine was bound to the oestradiol than poly-l-lysine. Oestradiol columns bound more protein from both the histone and acidic protein fraction than did columns of oestrone. Oestradiol bound more acidic protein than testosterone or progesterone but this difference was not evident with the histone fraction. Equilibrium dialysis experiments showed that the ability of a protein to bind to oestradiol was not related to its association constant with [6,7-3H] oestradiol. The acidic nuclear proteins had a higher association constant than the histone fraction. These results are discussed in relation to the purification of oestradiol receptors and to the binding of [6,7-3H]oestradiol in vivo.