|Protein Name||Complement factor B|
|Ref Sequence ID||NP_001035616.1|
|Protein Existence Status||Reviewed: Experimental evidence at protein level|
|Protein Function||key glycoprotein in the alternative pathway of complement activation; role in assembly of the C3 convertase complex by association with a C3b molecule; unusual type of serine proteinase. Complement component factor B (Bf), the second component of the alternative complement pathway, has thrombin-like activity, which is supported by a characteristic homology of the trypsin-like domain of Bf to that of thrombin.|
|Biochemical Properties||Bb fragment contains 11 cysteine residues; three commonly conserved disulphide bonds are present and are represented by disulphide bridges linking Cys-252 to Cys-286, Cys-396 to Cys-423 and Cys-436 to Cys-466; homology with thrombin; sequence containing the catalytic residues is considerably longer than that of other serine proteinases;|
|Significance in milk||immune protection against environmental pathogens|
|PTMs||Glycosylated; glucose is covalently attached; sialylated complex biantennary sugars|
| Site(s) of PTM(s) |
|Predicted Disorder Regions||NA|
|TM Helix Prediction||No TM helices|
|Significance of PTMs||N-linked oligosaccharide may be involved in the regulation of FB binding to C3b|
|Bibliography||1. Christie, D. L., & Gagnon, J. (1983). Amino acid sequence of the Bb fragment from complement factor B. Sequence of the major cyanogen bromide-cleavage peptide (CB-II) and completion of the sequence of the Bb fragment. Biochemical Journal, 209(1), 61–70. https://doi.org/10.1042/bj2090061. |
2. Niemann, M. A., Bhown, A. S., & Miller, E. J. (1991). The principal site of glycation of human complement Factor B. Biochemical Journal, 274(2), 473–480. https://doi.org/10.1042/bj2740473.
3. Rainard, P. (2002). Complement factor B and the alternative pathway of complement activation in bovine milk. The Journal of Dairy Research, 69(1), 1–12. https://doi.org/10.1017/s0022029901005337.
4. Davrinche, C., Abbal, M., & Clerc, A. (1990). Molecular characterization of human complement factor B subtypes. Immunogenetics, 32(5), 309–312. https://doi.org/10.1007/bf00211644. 5.Takahashi K, Banda NK, Holers VM, Van Cott EM. Complement component factor B has thrombin-like activity. Biochem Biophys Res Commun. 2021 May 7;552:17-22. doi: 10.1016/j.bbrc.2021.02.134. Epub 2021 Mar 16. PMID: 33740660; PMCID: PMC8035301.