Complement factor B

Complement factor B is a protein that in humans is encoded by the CFB gene.^[5]

CFB
Available structures PDB Ortholog search: PDBe RCSB List of PDB id codes 3HS0, 1DLE, 1Q0P, 1RRK, 1RS0, 1RTK, 2OK5, 2WIN, 2XWB, 2XWJ, 3HRZ
Identifiers
Aliases	CFB, Cfb, AI195813, AI255840, Bf, C2, Fb, H2-Bf, AHUS4, ARMD14, BFD, CFAB, CFBD, FBI12, GBG, PBF2, complement factor B
External IDs	OMIM: 138470; MGI: 105975; HomoloGene: 1292; GeneCards: CFB; OMA:CFB - orthologs
Gene location (Human) Chr. Chromosome 6 (human)[1] Band 6p21.33 Start 31,945,650 bp[1] End 31,952,084 bp[1]
Gene location (Mouse) Chr. Chromosome 17 (mouse)[2] Band 17 B1|17 18.41 cM Start 35,075,350 bp[2] End 35,081,494 bp[2]
RNA expression pattern Bgee Human Mouse (ortholog) Top expressed in right lobe of liver gallbladder appendix duodenum islet of Langerhans olfactory zone of nasal mucosa Descending thoracic aorta gastric mucosa right coronary artery human kidney Top expressed in proximal tubule right kidney human kidney white adipose tissue hepatobiliary system liver jejunum ileum colon duodenum More reference expression data BioGPS More reference expression data
Gene ontology Molecular function peptidase activity serine-type peptidase activity serine-type endopeptidase activity hydrolase activity complement binding protein binding Cellular component extracellular region plasma membrane blood microparticle extracellular exosome extracellular space Biological process complement activation regulation of complement activation proteolysis immune system process complement activation, alternative pathway innate immune response Sources:Amigo / QuickGO
Orthologs Species Human Mouse Entrez 629 14962 Ensembl ENSG00000243570 ENSG00000239754 ENSG00000243649 ENSG00000241253 ENSG00000242335 ENSG00000241534 ENSG00000204359 ENSMUSG00000090231 UniProt P00751 P04186 RefSeq (mRNA) NM_001710 NM_001142706 NM_008198 RefSeq (protein) NP_001701 NP_001136178 NP_032224 NP_001389804 Location (UCSC) Chr 6: 31.95 – 31.95 Mb Chr 17: 35.08 – 35.08 Mb PubMed search [3] [4]
Wikidata
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Function

This gene encodes complement factor B, a component of the alternative pathway of complement activation. Factor B circulates in the blood as a single chain polypeptide. Upon activation of the alternative pathway, it is cleaved by complement factor D yielding the noncatalytic chain Ba and the catalytic subunit Bb. The active subunit Bb is a serine protease that associates with C3b to form the alternative pathway C3 convertase. Bb is involved in the proliferation of preactivated B lymphocytes, while Ba inhibits their proliferation. This gene localizes to the major histocompatibility complex (MHC class III) region on chromosome 6. This cluster includes several genes involved in regulation of the immune reaction. The polyadenylation site of this gene is 421 bp from the 5' end of the gene for complement component 2.^[5]

Alternative pathway. (Some labels are in Polish.)

Complement tests

C4 (C)	FB (A)	C3	CH50	Conditions
·	↓	↓	↓	PSG, C3 NeF AA
↓	·	↓	·	HAE, C4D
·	·	·	↓	TCPD
↓	·/↓	↓	↓	SLE
↑	↑	↑	↑	inflammation