Complement C3: a molecular mosaic of binding sites.
Many of the biological activities of the complement system are mediated by C3, the third complement component, and its proteolytic fragments. At the same time, several of the molecules which regulate complement activation target their action at the C3 molecule. Accordingly, the C3 molecule is equipped with multiple binding sites for at least 14 other complement or complement-related proteins. As described in this review, major progress has been made recently in the identification of the C3 binding sites and the residues involved. Yet this has exposed only the "tip of the iceberg". A novel technique which may facilitate the elucidation of the active sites in C3 is presented. Finally, based on the current knowledge on the C3 molecule, a hypothetical model of the molecular organization of this molecule and its binding sites is presented.
Fishelson
Z
Z
Department of Chemical Immunology, Weizmann Institute of Science, Rehovot, Israel.
D000818:Animals; D001665:Binding Sites; D003167:Complement Activation; D003176:Complement C3 / Q000737:chemistry / Q000502:physiology* / Q000648:ultrastructure; D003180:Complement C3b Inactivator Proteins / Q000378:metabolism; D011415:Complement Factor B / Q000378:metabolism; D017242:Complement Factor H; D003545:Cysteine / Q000737:chemistry; D006801:Humans; D011487:Protein Conformation
C493495:CFH protein, human; D003176:Complement C3; D003180:Complement C3b Inactivator Proteins; D017242:Complement Factor H; D011415:Complement Factor B; D003545:Cysteine