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Importance of the α 3 ‐fragment of complement C4 for the binding with C4b‐binding protein
Author(s) -
Hessing Martin,
van't Veer Cornells,
Hackeng Tilman M.,
Bouma Bonno N.,
Iwanaga Sadaaki
Publication year - 1990
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(90)80389-z
Subject(s) - biochemistry , complement factor i , complement system , chemistry , trypsin , classical complement pathway , protease , peptide sequence , microbiology and biotechnology , biology , antibody , enzyme , gene , immunology
The human regulatory complement component C4b‐binding protein (C4BP) is a multimene plasma protein, which regulates the classical pathway of the complement system. C4BP functions as a cofactor to factor 1 in the degradation of C4b and accelerates the decay rate of the C4b2a complex. Previously, we have demonstrated that monoclonal antibodies (C4‐2 and 9) directed against the α'‐chain of C4b inhibit the binding of C4b to C4BP. In order to identify the structural domain of C4b that binds C4BP, proteolytic fragments of C4 were generated with trypsin and Staphylococcus aureus V8 protease. Sodium dodecyl sulfate polyacrylamide gel electrophoresis, immunoblotting and amino acid sequence analysis of the proteolytic fragments reactive with the anti‐C4 mAb's revealed that the residues Ala 738 ‐Arg 826 of the α 3 ‐fragment of C4b are important for the interaction with C4BP.