Cleavage of C2 by C1̄s̄ into the antigenically distinct fragments C2a and C2b: Demonstration of binding of C2b to C4b
AUTOR(ES)
Nagasawa, Shigeharu
RESUMO
The activation of complement component C2 by C1̄s̄ is a major reaction step leading to the assembly of two related macromolecular enzymes in the classical complement pathway C3 convertase and C5 convertase. The present studies clearly document the smaller fragment, C2b, that results when human C2 reacts with C1̄s̄. We have identified and characterized C2b (34,000 daltons) as a single protein on disc electrophoresis and immunoelectrophoresis. C2a (73,000 daltons), the larger fragment from this reaction, has a more acidic nature and C2b is more basic. These fragments can also be detected by their different antigenic determinants. When the C2-C4b complex is activated in the fluid phase by C1̄s̄ and allowed to decay, it dissociates into C2a and the C2b-C4b complex. Furthermore, when C2 is bound to C4b-Sepharose and then reacted with C1̄s̄, only the C2a fragment is released from the solid phase C2-C4b-Sepharose into the fluid phase, and the C2b fragment remains noncovalently bound to C4b-Sepharose. These results suggest that the C2b portion of C2 contains a stable binding site for C4b and, after the decay release of C2a from this C3 convertase, the C2b fragment remains bound. Thus, the decay release of C2a may represent a temperature-dependent dissociation from C2b.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=431380Documentos Relacionados
- Distinct roles of C2A and C2B domains of synaptotagmin in the regulation of exocytosis in adrenal chromaffin cells
- C2A activates a cryptic Ca2+-triggered membrane penetration activity within the C2B domain of synaptotagmin I
- Biotransformation of Sisomicin to Gentamicin C2b
- A restriction fragment of the C2 gene is a unique marker for C2 deficiency and the uncommon C2 allele C2*B (a marker for type 1 diabetes).
- The Ca2+ Affinity of Synaptotagmin 1 Is Markedly Increased by a Specific Interaction of Its C2B Domain with Phosphatidylinositol 4,5-Bisphosphate