Reversible denaturation of the estrogen receptor and estimation of polypeptide chain molecular weight

The estrogen receptor protein loses its ability to bind to estrogens upon denaturation with sodium dodecyl sulfate and 2-mercaptoethanol. Binding activity is recovered at 60-80% efficiency upon removal of the denaturants, equilibration with 6 M guanidine hydrochloride, and dilution into buffer containing estrogen. Renatured receptor is similar to native receptor in affinity for 17 beta-estradiol and ability to bind DNA. Detection of receptor activity after sodium dodecyl sulfate-polyacrylamide gel electrophoresis of uterine or pituitary cytosol or of uterine nuclear extracts reveals a single unique polypeptide species of 65,000 mol wt.