Laboratory for Molecular Diagnostics
Center for Nephrology and Metabolic Disorders
The CFB gene encodes a stimulating factor to the alternative complement pathway. Gain-of-function mutations have been described in atypical HUS and age-related macula degeneration.
The N-terminal fragment, Ba, is released during activation. It is composed of three complement control protein (CCP) domains. The active fragment Bb attains a dumbbell shape, and consists of two domains, one on each side. The N-terminal is a von Willebrand factor type A (vWFA) domain, and the C-terminal domain is a serine protease (SP). The vWFA domain (202 residues) shows structural similarities to the I domain of integrins. This domain contains a motif called Mg ion-dependent adhesion site (MIDAS), which is supposed to take part in C3b binding and SP activation. The Asn residue at codon position 260 is glycosylated. The SP domain consists of 283 residues. The proteolytic site is opposite the MIDAS motif.[Error: Macro 'ref' doesn't exist]
Before activation, factor B circulates in the blood as a single polypeptide chain.
Nativ Factor B is cleaved and activated by Factor D when bound to C3b. Ba is released, and the remaining complex C3bBb is a proficient C3-convertase that accelerates C3 activation by a positive feedback loop. The complex C3bBb is inherently unstable and easily dissociates. This inactivation is promoted by MCP, CFH, and CFI.
| Clinic | Method | Carrier testing |
| Turnaround | 5 days | |
| Specimen type | genomic DNA |
| Clinic | Method | Massive parallel sequencing |
| Turnaround | 25 days | |
| Specimen type | genomic DNA |
| Clinic | Method | Genomic sequencing of the entire coding region |
| Turnaround | 25 days | |
| Specimen type | genomic DNA |
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