Purification and properties of a progesterone-induced basic glycoprotein from the uterine fluids of pigs.
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The proteins present in the uterine secretions of pigs change both quantitatively and qualitatively during the normal estrous cycle. One of these proteins, which comprises about 15% of the total at Day 15 after estrus, is strongly basic and migrates toward the cathode during polyacrylamide gel electrophoresis at pH 7.0. It also has a characteristic lavender color with an extinction maximum at 545 nm ( = 1.76 x 103) and gives a positive reaction with periodic acid Schiff stain. In nonpregnant animals this protein is present in the uterus only between Days 12 and 16 after estrus but is absent from serum. It can, however, be induced at approximately the same time in ovariectomized animals given daily doses of progesterone or progesterone plus estrogen. Estrogen alone is ineffective. The protein has been purified from both normal and ovariectomized animals given progesterone by successive chromatography on Sephadex G 100 and CM cellulose. It was homogeneous as determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis and by immunodiffusion criteria. The protein has a molecular weight of about 32,000 and an isoelectric point at approximately pH 9.7. Large amounts of basic amino acids are present and the molecule is about 12.5% carbohydrate by weight. Antiserum prepared against this protein does not cross react with extracts from tissues other than the uterus.