C3b is the larger of two elements formed by the cleavage of complement component 3, and is considered an important part of the innate immune system. C3b is potent in opsonization: tagging pathogens, immune complexes (antigen - antibody), and apoptotic cells for phagocytosis.

C3b is a highly unstable molecule that has a unique thioester that allows covalent binding to a microbial cell. Some C3b fragments bind to the target cell, where they act as opsonins. In the classic pathway, most C3b is found in an AbC4bC2aC3b complex on the cell surface, which is called the C5 convertase .

2002年3月22日 · Complement receptor type 1 (CR1 or CD35) is a multiple modular protein that mediates the immune adherence phenomenon, a fundamental event for destroying microbes and initiating an immunological response. It fulfills this role …

2006年10月15日 · Here we present a structure of C3b that reveals a marked loss of secondary structure in the CUB (for ‘complement C1r/C1s, Uegf, Bmp1’) domain, which together with the resulting translocation of...

C3b (and C4b) contains a labile thioester bond that once hydrolyzed, may form a covalent ester or amide bond with cell surface glycoconjugates or immune complexes. The C3b generated by the C3 convertases of the classical/lectin or alternative pathways joins them in forming a C5 converting enzyme, acting specifically on complement C5 and ...

2023年6月8日 · Here, we revealed that complement component 3 (C3) is remarkably upregulated in paclitaxel (PTX)-resistant non-small cell lung cancer (NSCLC) cells and that knockdown of C3 promoted PTX-induced...

2006年10月15日 · Central to the complement system is the activated form of C3, called C3b, which attaches covalently to target surfaces 3 to amplify complement response, label cells for phagocytosis and...

2025年1月14日 · As part of the complement system, C3b is essential for tagging foreign invaders, making them more recognizable to immune cells. Understanding how C3b functions within the broader context of opsonization and immune activation reveals its …

2006年11月9日 · Central to the complement system is the activated form of C3, called C3b, which attaches covalently to target surfaces to amplify complement response, label cells for phagocytosis and stimulate the adaptive immune response. C3b consists of 1,560 amino-acid residues and has 12 domains. It binds various proteins and receptors to effect its functions.

2010年12月24日 · We present crystal structures of the pro-convertase C3bB at 4 angstrom resolution and its complex with factor D at 3.5 angstrom resolution. Our data show how factor B binding to C3b forms an open “activation” state of C3bB.