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.

2022年1月1日 · Some of the most fundamental features of C3 biochemistry can be understood by examining the structures of C3, C3b, and C3c, including (i) how the α and β chains relate to one another in the fully-matured molecule, (ii) how the intramolecular thioester required for opsonization remains protected in native C3, yet becomes accessible upon ...

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 the surface of a pathogen. This binding is a specific interaction that occurs when C3b recognizes molecular patterns on the pathogen’s surface.

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...

2017年4月4日 · Central to its function is C3, an abundant multi-domain plasma protein of ~185 kDa that, once activated by distinct initiation pathways, forms the opsonin C3b, which binds covalently to target surfaces (Fig. 1) (2, 3).

The solution structure of complement C3b is crucial for the understanding of complement activation and regulation. C3b is generated by the removal of C3a from C3. Hydrolysis of the C3 thioester produces C3u, an analog of C3b. C3b cleavage results in C3c and C3d (thioester-containing domain; TED).

Complement Component C3b is a serum protein that plays a crucial role in innate and adaptive immunity by binding covalently to pathogens, acting as an opsonin to target them for destruction by phagocytes.

The complement C3b functional assay is a laboratory technique designed to evaluate the activity and functionality of the C3b component within the complement system across various samples. This assessment is achievable through the use of hemolytic tests and solid-phase sandwich ELISA methods.

2009年1月20日 · Using single-particle electron microscopy we have determined the 3-dimensional structures of the C3bB and the C3bBb complexes at ≈27Å resolution. The C3bB structure shows that fB undergoes a dramatic conformational change upon binding to C3b.

Surface-bound C3b is necessary in all three pathways for efficient activation of C5 and formation of C5b-9 complexes that lyse the target cell membrane. Surface-bound C3b and its breakdown products iC3b and C3d are recognized by numerous receptors on lymphoid and phagocytic cells which use the C3b ligand to stimulate antigen presentation to ...