[Isolation and characterization of a 19S-alpha1-glycoprotein from human erythrocytes and its identification as placenta protein PP6].

A high molecular weight protein was isolated from the hemolysate of washed human erythrocytes by a procedure involving ion exchange chromatography, ammonium sulfate fractionation and gel filtration. The purified protein was found to have a sedimentation coefficient of 18,68S and a molecular weight of 8 times 10-5 to 1 times 10-6 daltons. In the presence of sodium dodezylsulfate the molecules are dissociated into at least four different subunits having molecular weights ranging from 12,000 to 30,000 daltons. The protein has the electrophoretic mobility of an alpha-1-globulin and an isoelectric point of pH 4.75. The chemical analysis revealed that the protein is chemical and immunochemical properties the 19S-alpha-1-glycoprotein from human erythrocytes was shown to be identical with the protein PP6 isolated from huamn placentae. The content of this protein in packed red blood cells was determined to be around 50 mg per 100 ml.