Purification, characterization and identification of an agglutinin in human serum.

A serum protein named agglutinin is able to induce mitochondria to agglutinate. The protein has been purified from human serum by chromatography on DE-52. Sephadex G-200 and immunoglobulin-Sepharose 4B columns. Agglutinin is a glycoprotein that migrates electrophoretically as a gamma-globulin. Its molecular weight was determined to be 50,000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Monospecific antiserum prepared against the agglutinin was found to be identical with anti-beta 2-glycoprotein I and agglutinating activity could be adsorbed on anti-beta 2-glycoprotein I-Sepharose 4B columns. Thus, the agglutinin has been identified as beta 2-glycoprotein I. The reaction between mitochondria and agglutinin shows positive cooperativity, which is independent on the stage of purification of agglutinin. The agglutinating activity could be diminished (inhibited) by acidic non-soluble lipids such as oleic acid, phosphatidic acid, phosphatidyl serine and phosphatidyl inositol.