PURIFICATION OF THE CYTOPLASMIC OESTROGEN RECEPTOR FROM MAMMARY TUMOURS INDUCED IN RATS WITH DIMETHYLBENZANTHRACENE

Abstract
The oestrogen receptor from mammary tumours induced in rats by dimethylbenz(a)-anthracene has been extensively purified by affinity chromatography and isoelectric focusing. The unpurified cytoplasmic 8 S oestrogen receptor had a molecular weight of 240 000, a Stokes radius of 5·4 nm and a frictional ratio of 1·32; the Km (dissociation constant) at 4 °C for [3H]oestradiol-17β was 0·184 nmol/l. At the end of affinity chromatography the molecular weight was still 240 000 but under the conditions of isoelectric focusing it was reduced to 110 000, with a Stokes radius of 4·0 nm, a frictional ratio of 1·26 and an isoelectric point of 6·4.