MICROHETEROGENEITY OF HUMAN KININOGEN BY ISOELECTRIC FOCUSING AND CROSSED IMMUNOELECTROPHORESIS

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Abstract
LMW [low MW] kininogen was isolated from whole human plasma by gel filtration on Sephadex G-200 (Kav 0.34) followed by DEAE-chromatography according to earlier established methods. Further purification was performed with specific Sepharose-antibody columns to remove protein contaminants, avoiding procedures which may denature kininogen. The microheterogeneity was investigated by isoelectric focusing in column in the pH-gradients 3.5-10, 4-6 and 3.5-5. Kininogen components were determined by single radial immunodiffusion against monospecific anti-human kininogen serum, in comparison with focusing of whole plasma. Of isolated as well as whole plasma kininogen 40% focused at pI 4.5; the respective focusing ranges were pI 4.4-4.7 (60-80%) and pI 4.3-4.6 (92%). The results were verified by crossed immunoelectrophoresis. The pI 4.5 component was apparently the main native form of human kininogen as shown by focusing of whole human blood bank plasma. Earlier described difficulty of separating kininogen and .alpha.2HS-glycoprotein was verified by crossed immunoelectrophoresis which showed approximately 7 kininogen components after focusing in polyacrylamide gel electrophoresis at pI 4.5-5.0 and 4 .alpha.2HS components at pI 4.2-4.6.