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.

C3：血浆中的C3可自然地、缓慢地裂解，持续产生少量的C3b，释入液相中的C3b迅速被I因子灭活。

C3b充当视蛋白（opsin），有助于进一步放大补体激活以及帮助吞噬作用。 此外，C3b复合物与C3转化酶形成C5转化酶：C3bBbC3b和C4bC2aC3b。

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 ...

C3bBb catalyzes an avalanche of C3a and C3b from C3. C3b opsonization of bacteria triggers their phagocytosis and neutralization by neutrophils and MPs. The recruitment of an additional C3b molecule to C3bBb leads to the formation of the C3bBbC3b complex, the C5 convertase that cleaves C5 into C5a and C5b.

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.

2006年12月12日 · C3 convertase activates C3 by cleaving the alpha chain, releasing C3a anaphylatoxin and generating C3b (beta chain + alpha' chain). Forms the pro-C3-convertase enzyme complex by interacting with Complement factor B Bb fragment (Bb), which is then stabilized by binding CFP, allowing the complex to become active …

2006年10月15日 · Central to the complement system is the activated form of C3, called C3b, which attaches covalently to target surfaces3 to amplify complement response, label cells for phagocytosis and stimulate...

In this context, C3b not only amplifies the complement response via convertase formation but also acts as an effector itself that mediated functions in innate and adaptive immunity. 12 Via binding to complement receptor 1 (CR1; CD35) on immune cells, it confers immune adherence that enables the shuttling of opsonized cells to the spleen and liver.

2025年1月14日 · C3b opsonization enhances the immune system’s ability to identify and eliminate pathogens. This process begins when C3b, a fragment of the complement protein C3, binds to …