Analysis of the molecular species of the chick oviduct progesterone receptor using isoelectric focusing

Abstract

Conditions are described for the preparative isoelectric focusing in flat beds of Sephadex of the progesterone [P] receptor from the chick oviduct. The method allows the fractionation of the receptor into 2 molecular species, one focusing at pI [isoelectric point] 6 and the other at pI 7 with good purification and recovery. The pI 6 and pI 7 receptor species were purified 2- and 26-fold, respectively. The assaying of the focused fractions with the charcoal binding method provides an accurate identification and quantitation of the [3H]P receptor. The method is reproducible in recovery, quantitation, and resolution of the 2 receptor species. The receptor with an apparent pI of 6 sediments at .apprx. 4 S on linear sucrose gradients, while the receptor with an apparent pI of 7 sediments at .apprx. 3.5 S. On the basis of the sedimentation values and elution patterns from DEAE chromatography, the pI 6 component is equivalent to the B receptor species and the pI 7 component is equivalent to the A receptor species described previously.