Alternative complement activation

Stable Identifier
Homo sapiens
Locations in the PathwayBrowser

The proteins participating in alternative pathway activation are C3 (and C3b), the factors B, D, and properdin. In the first place, alternative pathway activation is a positive feedback mechanism to increase C3b. When C3b binds covalently to sugars on a cell surface, it can become protected. Then Factor B binds to C3b. In the presence of Factor D, bound Factor B is cleaved to Ba and Bb. Bb contains the active site for a C3 convertase. Properdin then binds to C3bBb to stabilize the C3bBb convertase on cell surface leading to cleavage of C3. Finally, a C3bBb3b complex forms and this is a C5 convertase.

Literature References
PubMed ID Title Journal Year
162484 Activation of the alternative complement pathway CRC Crit Rev Immunol 1979
Participant Of
Event Information
Orthologous Events