Structural assignment and extractability of microsomal estradiol receptors.

Two electrophoretically different forms of estradiol receptor can be extracted from crude porcine endometrium microsomes with low ionic strength buffers. Better yields (approximately 50%) of both forms are obtained in the presence of Surfynol 485. Dithiothreitol boosts the solubilization of basic receptor. Together, Surfynol and dithiothreitol have a more than additive effect, amounting to 3-4 times the quantities of receptor extracted with plain buffer. Trypsin more than triples the yields obtained with Surfynol/dithiothreitol, while degrading both receptor forms to a characteristic fragment. Hyaluronoglucosaminidase is somewhat less effective than trypsin. It changes acidic receptor to basic. The proportions of acidic/basic receptor in microsomal subfractions are different. Rough endoplasmic reticulum contains almost exclusively basic receptor. Smooth membranes are rich in acidic receptor. The efficacy of both enzymes is closely related to the proportion of acidic receptor found in Surfynol/dithiothreitol extracts.