Download MendeleyStructure of complement component c2a: implications for convertase formation and substrate binding.
Milder, F.J., Raaijmakers, H.C., Vandeputte, M.D., Schouten, A., Huizinga, E.G., Romijn, R.A., Hemrika, W., Roos, A., Daha, M.R., Gros, P.(2006) Structure 14: 1587-1597
- PubMed: 17027507
- DOI: https://doi.org/10.1016/j.str.2006.08.008
- Primary Citation of Related Structures:
2I6Q, 2I6S - PubMed Abstract:
C2a provides the catalytic center to the convertase complexes of the classical and lectin-binding pathways of complement activation. We determined two crystal structures of full-length C2a, with and without a pseudo ligand bound. Both structures reveal a near-active conformation of the catalytic center of the serine protease domains, while the von Willebrand factor A-type domains display an intermediate activation state of helix alpha7 with an open, activated metal-ion-dependent adhesion site. The open adhesion site likely serves to enhance the affinity for the ligand C4b, similar to "inside-out" signaling in integrins. Surprisingly, the N-terminal residues of C2a are buried in a crevice near helix alpha7, indicative of a structural switch between C2 and C2a. Extended loops on the protease domain possibly envelop the protruding anaphylatoxin domain of the substrate C3. Together with a putative substrate-induced completion of the oxyanion hole, this may contribute to the high substrate specificity of the convertases.
Organizational Affiliation:
Crystal and Structural Chemistry, Bijvoet Center for Biomolecular Research, Faculty of Science, Utrecht University, 3584 CH Utrecht, The Netherlands.
