Isolation of a beta 2-glycoprotein from human serum after precipitation with dextran sulfate and manganese chloride.
A new procedure was developed which affords isolation from among the euglobulins of human serum a beta 2-glycoprotein with a high degree of immunological and electrophoretic homogeneity. The isolated protein displays specific binding affinity for the activated form of the C4 component (C4b), and was identified by immunological and physico-chemical criteria as the C4 binding protein. The isolation procedure comprises the following steps: precipitation of euglobulins from serum at pH 5.5 and low ionic strength; precipitation of beta-lipoproteins from the redissolved precipitate with dextran sulfate and CaCl2; precipitation of a fraction of the lipoprotein-free euglobulins with dextran sulfate and MnCl2; redissolution of the precipitate and eventually chromatography on Sepharose 4B. The overall yield was between 15 and 20 per cent. The final product, devoid of immunologically detectable protein contaminants, was a homogeneous proline-rich monomeric beta 2-glycoprotein made up of eight disulfide-bonded polypeptide chains of the same molecular weight 63,000 +/- 3,000. Under non-reducing conditions, the molecular weight of both the native and the SDS-treated protein was 490,000 +/- 25,000. A monospecific antiserum to the isolated protein was raised in rabbits and used for the quantitation of the protein in sera of normal fasting donors; a mean concentration of 25 mg per 100 ml of serum (1 SD: 5) was established.
D002712:Chlorides; D002850:Chromatography, Gel; D016264:Dextran Sulfate; D003911:Dextrans; D006023:Glycoproteins / Q000097:blood / Q000302:isolation & purification*; D006801:Humans; D008345:Manganese; D017895:Manganese Compounds; D008970:Molecular Weight; D053482:beta 2-Glycoprotein I
D002712:Chlorides; D003911:Dextrans; D006023:Glycoproteins; D017895:Manganese Compounds; D053482:beta 2-Glycoprotein I; D008345:Manganese; D016264:Dextran Sulfate; C025340:manganese chloride