CFB (Complement Factor B)
Key component of the alternative complement pathway
Gene Information Card
| Symbol | CFB |
|---|---|
| Full Name | Complement Factor B |
| Gene Type | Protein coding |
| Chromosomal Location | 6p21.33 |
| NCBI Gene ID | 629 ncbi.nlm.nih.gov/gene/629 |
| Ensembl ID | ENSG00000166226 |
| UniProt ID | P00751 |
| OMIM ID | 138470 |
| HGNC ID | 1037 |
| Aliases | BF, BFD, CFAB, CFBD, GBG, H2-Bf, PBF2 |
Description
The CFB gene encodes complement factor B, a serine protease that is a central component of the alternative complement pathway. Factor B binds to C3b to form the C3 convertase (C3bBb), which cleaves C3 to initiate the amplification loop of complement activation. This gene is located in the MHC class III region on chromosome 6. Mutations in CFB are associated with atypical hemolytic uremic syndrome (aHUS), C3 glomerulopathy, and age-related macular degeneration (AMD).
Disease Associations
| Disease category | Pathophysiological mechanism | Genomic evidence |
|---|---|---|
| Atypical hemolytic uremic syndrome (aHUS) | Gain-of-function mutations in CFB lead to uncontrolled alternative pathway activation, causing endothelial damage and microvascular thrombosis. | ClinVar, OMIM |
| C3 glomerulopathy (C3G) | Dysregulation of the alternative pathway due to CFB mutations results in excessive C3 deposition in glomeruli. | ClinVar, OMIM |
| Age-related macular degeneration (AMD) | CFB variants (e.g., R32Q) alter complement activation, contributing to drusen formation and retinal degeneration. | NCBI Gene, OMIM |
| Complement factor B deficiency | Loss-of-function mutations cause impaired alternative pathway activity, leading to increased susceptibility to Neisseria infections. | OMIM, ClinVar |
Expression Profile
Tissue Expression
| Tissue | nTPM | level |
|---|---|---|
| Liver | 57.2 | High |
| Adipose tissue | 12.1 | Medium |
| Lung | 8.5 | Medium |
| Kidney | 6.3 | Medium |
| Spleen | 5.9 | Medium |
| Pancreas | 4.2 | Low |
| Heart | 3.1 | Low |
| Brain | 0.8 | Not detected |
Cell Line Expression
| Cell Line | nTPM | Notes |
|---|---|---|
| HepG2 (liver) | 62.5 | High expression |
| A549 (lung) | 15.3 | Moderate expression |
| HEK293 (embryonic kidney) | 8.7 | Moderate expression |
| K562 (leukemia) | 2.1 | Low expression |
| MCF7 (breast) | 1.4 | Low expression |
Data source：Human Protein Atlas（proteinatlas.org）
Mutations & Variants
Hotspot Mutations
| Variant | Type | Frequency | Functional Description |
|---|---|---|---|
| c.95G>A (p.Arg32Gln) | Missense | Common in AMD | Gain-of-function; increases C3 convertase activity |
| c.967A>G (p.Lys323Glu) | Missense | Rare in aHUS | Gain-of-function; enhances C3b binding |
| c.1690C>T (p.Arg564Cys) | Missense | Rare in C3G | Gain-of-function; stabilizes convertase |
| c.1A>G (p.Met1?) | Start loss | Very rare | Loss-of-function; complete deficiency |
Mutation functional classification
Loss of Function (LOF)
Rare start-loss or nonsense mutations cause complete CFB deficiency, impairing alternative pathway activation and increasing infection risk.
Gain of Function (GOF)
Missense mutations (e.g., R32Q, K323E, R564C) enhance C3 convertase stability or activity, leading to complement overactivation and diseases like aHUS, C3G, and AMD.
Dominant Negative (DN)
No well-characterized dominant-negative mutations reported for CFB.
View complete mutation data：
Gene Ontology (GO)
Pathways
• Alternative complement pathway (Reactome: R-HSA-173736)
• Complement cascade (KEGG: hsa04610)
• Staphylococcus aureus infection (KEGG: hsa05150)
• Systemic lupus erythematosus (KEGG: hsa05322)
Protein Summary
Complement factor B (UniProt P00751) is a 764-amino-acid glycoprotein synthesized primarily in the liver. It circulates in plasma as a single-chain zymogen. Upon activation by factor D, it is cleaved into Ba and Bb fragments. The Bb fragment contains the serine protease domain and associates with C3b to form the alternative pathway C3 convertase (C3bBb). Factor B is essential for the amplification loop of complement activation, playing a critical role in innate immunity.
Related Services
Related Products
| Product name | Cat.No. | Species | Gene ID | |
|---|---|---|---|---|
| CFB Knockout HEK293 Cell Line | EDJ-KQ50154 | Human | 629 | Details Get a Quote |
| CFB Knockout HeLa Cell Line | EDJ-KQ52716 | Human | 629 | Details Get a Quote |
| CFB Knockout A-549 Cell Line | EDJ-KQ61187 | Human | 629 | Details Get a Quote |
| CFB Knockout HCT 116 Cell Line | EDJ-KQ69679 | Human | 629 | Details Get a Quote |
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