Hydrophobic interaction chromatography of the rabbit uterine progesterone receptor

The chromatographic behavior of the rabbit uterine progesterone receptor interaction on several different hydrophobic matrices was characterized. Receptor, prepared in 0.6 M NaCl, exhibited a progressive retardation of elution, followed by retention, on a series of alkyl agarose columns as the length of the alkyl chain [(CH2)nH-] increased (n = 0-10), reflecting the presence of hydrophobic regions on the protein. Adsorption did not occur directly at the steroid binding site of the molecule and did not require activation to the DNA-binding form. Elution could be achieved by a decrease in the ionic strength of the buffer or the addition of glycerol, resulting in partial purification of receptor. Receptor bound tightly to phenyl agarose, although elution of the receptor under mild conditions (decreasing salt gradient, increasing glycerol gradient) resulted in poor yield and only modest purification. Passage of the non-activated progesterone receptor over Reactive Blue Sepharose effectively removed albumin, presumably by a hydrophobic interaction, although receptor was not retained. In the activated form, approximately 25% of receptor was bound to Reactive Blue Sepharose, reflecting an interaction of the Cibacron Blue dye with the polynucleotide binding site of the receptor. Hydrophobic chromatography may be an important adjunct to methods for purification of the progesterone receptor.