Isolation and Characterization of α1-Acid Glycoprotein from Chimpanzee Plasma

Abstract

α1-Acid glycoprotein has been isolated in homogeneous form from Cohn's Fraction VI of chimpanzee plasma by carboxymethyl cellulose chromatography and also by electrofocusing. The sedimentation coefficient of this glycoprotein is 3.48 and the molecular weight is 39,000 as estimated by the Archibald sedimentation equilibrium method. By using sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the molecular weights of both chimpanzee and human α1-acid glycoprotein were found to be 40,000. General properties of chimpanzee α1-acid glycoprotein, including amino acid composition, carbohydrate composition, and COOH-terminal and NH2-terminal amino acids, closely resemble those of human α1-acid glycoprotein. By electrofocusing, the isoelectric points of both human and chimpanzee α1-acid glycoprotein were found to be 1.82. In spite of the close resemblance between human and chimpanzee α1-acid glycoprotein in chemical and physical properties, and the fact that they appear immunologically identical by the Ouchterlony double diffusion technique, an immunological difference between these two glycoproteins has been shown by quantitative precipitin analysis. The results suggest that these two glycoproteins are different either in the oligosaccharide or in the peptide sequences, or possibly in both oligosaccharide and peptide structures.