[9] C3b inactivator and β1H

Deficiency of a surface membrane glycoprotein (Mo1) in man.

“…C3bi-coated sheep erythrocytes (EAC43bi) were made by incubating EAC43b with purified factor I (10 Mg/ml) and factor H (50 Ug/ml) (17) in Hanks' balanced salt solution containing Ca (1.27 mM) and Mg (1.23 mM) (HBSS) for I h at 370C as described (3). Alternatively, EAC43bi…”

Inhibition of phagocytosis of complement C3- or immunoglobulin G-coated particles and of C3bi binding by monoclonal antibodies to a monocyte-granulocyte membrane glycoprotein (Mol).

“…The Fab fragments of monoclonal antibodies were prepared as described (20) and purity of fragments shown by SDS PAGE analysis. Human C3, C3b dimers, ,BIH, and C3b inactivator were purified as described (2,(21)(22). CS was further purified by sequential affinity chromatography on Sepharose to which the Ig fraction of rabbit antibodies to human C5, 1 Abbreviations used in this paper: Es, sheep erythrocyte; HSA, human serum albumin; ORO, oil red 0; PAGE, polyacrylamide gel electrophoresis; RT, room temperature.…”

Complement factor I in health and disease

“…With improvement in protein purification methods, it was shown that more highly purified FI does not cleave C3b or C4b: an additional protein, a cofactor, was required, which formed a complex with C3b or C4b, and only the complex was attacked by FI. The soluble cofactors FH and C4BP were isolated from plasma in the 1970s, and the membrane-bound cofactors CR1 and MCP in the 1980s (summarised by (Crossley, 1981;Sim et al, 1993). Additional virus-encoded proteins, which mimic activities of the cofactor proteins were identified in vaccinia virus, herpes virus 8 and in the smallpox virus .…”

“…Studies on the polypeptide chain structure, and N-terminal amino acid sequence of isolated FI led to the conclusion that it was a serine protease but with atypical mode of action as it was not inhibited by the wide-spectrum serine protease inhibitor, DFP (diisopropyl fluorophosphate) (Crossley, 1981). Complete cDNA sequencing (Catterall et al, 1987;Goldberger et al, 1987) confirmed that FI had a typical serine protease domain, related to that of trypsin, with the conserved catalytic triad, Asp-Ser-His.…”