2OK5: Human Complement Factor B

Citation:
Abstract
Factor B is the central protease of the complement system of immune defense. Here, we present the crystal structure of human factor B at 2.3-A resolution, which reveals how the five-domain proenzyme is kept securely inactive. The canonical activation helix of the Von Willebrand factor A (VWA) domain is displaced by a helix from the preceding domain linker. The two helices conformationally link the scissile-activation peptide and the metal ion-dependent adhesion site required for binding of the ligand C3b. The data suggest that C3b binding displaces the three N-terminal control domains and reshuffles the two central helices. Reshuffling of the helices releases the scissile bond for final proteolytic activation and generates a new interface between the VWA domain and the serine protease domain. This allosteric mechanism is crucial for tight regulation of the complement-amplification step in the immune response.
PDB ID: 2OK5Download
MMDB ID: 44730
PDB Deposition Date: 2007/1/16
Updated in MMDB: 2012/12
Experimental Method:
x-ray diffraction
Resolution: 2.3  Å
Source Organism:
Similar Structures:
Biological Unit for 2OK5: monomeric; determined by author
Molecular Components in 2OK5
Label Count Molecule
Protein (1 molecule)
1
Complement Factor B(Gene symbol: CFB)
Molecule annotation
Chemicals (24 molecules)
1
6
2
1
3
4
4
13
* Click molecule labels to explore molecular sequence information.

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