Estradiol receptor of calf uterus: interactions with heparin-agarose and purification.

Abstract

Heparin attached covalently to agarose beads binds the native form of the estradiol receptor with very high affinity. Chondroitin sulfate does not bind to the receptor. When the receptor is complexed with hormone, the affinity is at least 10 times higher. Only the native and not the nuclear or the derived (i.e., after activation by a calcium-dependent enzyme) forms of the estradiol receptor interact with heparin. The native estradiol-receptor complex is purified to homogeneity after chromatography on columns of heparin-agarose, Sephadex G-200 and DEAE-cellulose, followed by 2 more Sephadex G-200 columns. The purified molecule is a single polypeptide of MW 69,000 by polyacrylamide gel electrophoresis in sodium dodecyl sulfate. The sedimentation coefficient on sucrose gradients is 4.3 S, the Stokes radius from gel filtration is 36.5 .ANG., and the isoelectric point is 6.4. The purified [3H]estradiol-receptor complex exchanges the radioactive hormone with estradiol or other estrogenic steroids, but not with testosterone, 5.alpha.-dihydrotestosterone, or progesterone.