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Action of the C3b-inactivator on the cell-bound C3b. 1979

S K Law, and D T Fearon, and R P Levine

The action of C3bINA and beta 1H on cell-bound C3b is described in this paper. The alpha-polypeptide of C3b that binds covalently to cell surfaces is cleaved by the C3bINA and beta 1H into two fragments: one of 60,000 (C3b alpha-60) and another of 40,000 (C3b alpha-40) daltons. The beta-chain of C3b is unaffected by the C3bINA and beta 1H. The three polypeptides, C3b alpha-60, C3b alpha-40, and C3 beta, are held together as a single unit by disulfide bonds. This unit, referred to as C3b' is covalently bound to cell surfaces via the C3b alpha-60 polypeptide. The conversion of C3b to C3b' by C3bINA and beta 1H abolishes the ability of the C3b-bearing cells to adhere to human erythrocytes as well as the ability to form, on the cell surface, the B, D, and properdin-dependent amplification C3-convertase. However, the agglutinability of the cells with either anti-C3c or anti-C3d is not affected. Treatment of the C3b'-bearing cells with trypsin releases fragments of C3b' into solution, leaving a polypeptide of 32,000 daltons covalently linked to the membrane. Since the trypsinized cells are agglutinable by anti-C3d but not by anti-C3c, the 32,000 dalton polypeptide appears to correspond antigenically to C3d.

UI MeSH Term Description Entries
D008565 Membrane Proteins Proteins which are found in membranes including cellular and intracellular membranes. They consist of two types, peripheral and integral proteins. They include most membrane-associated enzymes, antigenic proteins, transport proteins, and drug, hormone, and lectin receptors. Cell Membrane Protein,Cell Membrane Proteins,Cell Surface Protein,Cell Surface Proteins,Integral Membrane Proteins,Membrane-Associated Protein,Surface Protein,Surface Proteins,Integral Membrane Protein,Membrane Protein,Membrane-Associated Proteins,Membrane Associated Protein,Membrane Associated Proteins,Membrane Protein, Cell,Membrane Protein, Integral,Membrane Proteins, Integral,Protein, Cell Membrane,Protein, Cell Surface,Protein, Integral Membrane,Protein, Membrane,Protein, Membrane-Associated,Protein, Surface,Proteins, Cell Membrane,Proteins, Cell Surface,Proteins, Integral Membrane,Proteins, Membrane,Proteins, Membrane-Associated,Proteins, Surface,Surface Protein, Cell
D008970 Molecular Weight The sum of the weight of all the atoms in a molecule. Molecular Weights,Weight, Molecular,Weights, Molecular
D010455 Peptides Members of the class of compounds composed of AMINO ACIDS joined together by peptide bonds between adjacent amino acids into linear, branched or cyclical structures. OLIGOPEPTIDES are composed of approximately 2-12 amino acids. Polypeptides are composed of approximately 13 or more amino acids. PROTEINS are considered to be larger versions of peptides that can form into complex structures such as ENZYMES and RECEPTORS. Peptide,Polypeptide,Polypeptides
D011817 Rabbits A burrowing plant-eating mammal with hind limbs that are longer than its fore limbs. It belongs to the family Leporidae of the order Lagomorpha, and in contrast to hares, possesses 22 instead of 24 pairs of chromosomes. Belgian Hare,New Zealand Rabbit,New Zealand Rabbits,New Zealand White Rabbit,Rabbit,Rabbit, Domestic,Chinchilla Rabbits,NZW Rabbits,New Zealand White Rabbits,Oryctolagus cuniculus,Chinchilla Rabbit,Domestic Rabbit,Domestic Rabbits,Hare, Belgian,NZW Rabbit,Rabbit, Chinchilla,Rabbit, NZW,Rabbit, New Zealand,Rabbits, Chinchilla,Rabbits, Domestic,Rabbits, NZW,Rabbits, New Zealand,Zealand Rabbit, New,Zealand Rabbits, New,cuniculus, Oryctolagus
D003176 Complement C3 A glycoprotein that is central in both the classical and the alternative pathway of COMPLEMENT ACTIVATION. C3 can be cleaved into COMPLEMENT C3A and COMPLEMENT C3B, spontaneously at low level or by C3 CONVERTASE at high level. The smaller fragment C3a is an ANAPHYLATOXIN and mediator of local inflammatory process. The larger fragment C3b binds with C3 convertase to form C5 convertase. C3 Complement,C3 Precursor,Complement 3,Complement C3 Precursor,Complement Component 3,Precursor-Complement 3,Pro-C3,Pro-Complement 3,C3 Precursor, Complement,C3, Complement,Complement, C3,Component 3, Complement,Precursor Complement 3,Precursor, C3,Precursor, Complement C3,Pro C3,Pro Complement 3
D003179 Complement C3b The larger fragment generated from the cleavage of COMPLEMENT C3 by C3 CONVERTASE. It is a constituent of the ALTERNATIVE PATHWAY C3 CONVERTASE (C3bBb), and COMPLEMENT C5 CONVERTASES in both the classical (C4b2a3b) and the alternative (C3bBb3b) pathway. C3b participates in IMMUNE ADHERENCE REACTION and enhances PHAGOCYTOSIS. It can be inactivated (iC3b) or cleaved by various proteases to yield fragments such as COMPLEMENT C3C; COMPLEMENT C3D; C3e; C3f; and C3g. C3b Complement,C3bi,Complement 3b,Complement Component 3b,Inactivated C3b,iC3b,C3b, Complement,C3b, Inactivated,Complement, C3b,Component 3b, Complement
D003180 Complement C3b Inactivator Proteins Endogenous proteins that inhibit or inactivate COMPLEMENT C3B. They include COMPLEMENT FACTOR H and COMPLEMENT FACTOR I (C3b/C4b inactivator). They cleave or promote the cleavage of C3b into inactive fragments, and thus are important in the down-regulation of COMPLEMENT ACTIVATION and its cytolytic sequence. C3b Inactivators,C3b Inhibitors,Complement 3b Inactivators,Complement 3b Inhibitors,Complement C3b Inactivators,Complement C3b Inhibitor Proteins,Conglutinogen Activating Factors,Factors, Conglutinogen Activating,Inactivators, C3b,Inactivators, Complement 3b,Inactivators, Complement C3b,Inhibitors, C3b,Inhibitors, Complement 3b
D003181 Complement C4 A glycoprotein that is important in the activation of CLASSICAL COMPLEMENT PATHWAY. C4 is cleaved by the activated COMPLEMENT C1S into COMPLEMENT C4A and COMPLEMENT C4B. C4 Complement,C4 Complement Component,Complement 4,Complement C4, Precursor,Complement Component 4,Pro-C4,Pro-complement 4,C4, Complement,Complement Component, C4,Complement, C4,Component 4, Complement,Component, C4 Complement,Pro C4,Pro complement 4
D004591 Electrophoresis, Polyacrylamide Gel Electrophoresis in which a polyacrylamide gel is used as the diffusion medium. Polyacrylamide Gel Electrophoresis,SDS-PAGE,Sodium Dodecyl Sulfate-PAGE,Gel Electrophoresis, Polyacrylamide,SDS PAGE,Sodium Dodecyl Sulfate PAGE,Sodium Dodecyl Sulfate-PAGEs
D006168 Guinea Pigs A common name used for the genus Cavia. The most common species is Cavia porcellus which is the domesticated guinea pig used for pets and biomedical research. Cavia,Cavia porcellus,Guinea Pig,Pig, Guinea,Pigs, Guinea

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