TRYPSIN-ACTIVATED COMPLEX OF HUMAN FACTOR-B WITH COBRA VENOM FACTOR (CVF), CLEAVING C3 AND C5 AND GENERATING A LYTIC FACTOR FOR UNSENSITIZED GUINEA-PIG ERYTHROCYTES .2. PHYSICOCHEMICAL CHARACTERIZATION OF ACTIVATED COMPLEX

  • 1 January 1975
    • journal article
    • research article
    • Vol. 18  (4) , 205-214
Abstract
A complex CVF-B, between CVF and human factor B (B) [the 3rd component of complement (C3) proactivator] showed weak, short-lived enzymatic activity against C3. Once activated with trypsin, it showed strong, stable activity against C3 and C5. CVF-.hivin.B, an activated form of CVF-B complex, was not affected by the trypsin inhibitor diisopropylfluorophosphate and neuraminidase. Heating at 56.degree. C for 30 min completely destroyed its activity and heating at 50.degree. C for 30 min destroyed approximately half its activity. The activity of CVF-.hivin.B decreased markedly at pH 6.0 but was stable at pH 6.5-8.5. CVF-.hivin.B lost 90% of its activity on reduction with 1 mM dithiothreitol, and was completely adsorbed on a cellulose acetate membrane. CVF-.hivin.B was a complex of CVF and glycine-rich .gamma.-glycoprotein [ggg], with a molecular weight of 340,000. The CVF-.hivin.B molecule consisted of 4 polypeptide chains, 3 of which were derived from CVF and 1 from GGG. Hemolytically active CVF-.hivin.B may be formed from 2 molecules with 4-polypeptide chains linked by unknown bonds. Human, rat and guinea pig sera reacted with CVF-.hivin.B to generate a lytic factor. Human and sheep erythrocytes were not sensitive to the lytic factor generated by CVF-.hivin.B; liposomes prepared from their membrane lipids were equally sensitive to the lytic factor.