The Urate-Binding Alpha₁ -₂ Globulin: Isolation and Characterization of the Protein from Human Plasma

The urate-binding α_1-2 globulin has been isolated from human plasma in a highly purified state. The isolation procedure was based upon anion exchange chromatography of the plasma macromolecular fraction on DEAE-Sephadex columns followed by ammonium sulphate precipitations and preparative polyacrylamide gel electrophoresis. The urate-binding α_1-2 globulin is a rod-shaped glycoprotein with a molecular weight of 67000 as determined by dodecyl sulphate polyacrylamide gel electrophoresis and an isoelectric point of pH 4.6. In the presence of 6 N urea and mercaptoethanol respectively the protein does not split into subunits indicating that it might represent a single polypeptide chain. The urato-binding α_1-2 globulin contains 12.1% of carbohydrates including galactose, mannoso, galactosamine and sialic acid. The amino acid composition of the protein does not differ significantly from what is found in other plasma proteins except for the presence in automatic amino acid analysis of an hitherto unidentified compound. Further work is required in order to determine the number of binding sites for uric acid on the protein molecule.-The urate-binding α_1-2 globulin does not seem to be identical to any previously characterized protein from human blood.