Seroatlas · Human Serome Atlas

CFI

Complement factor I

Also known as: C3b-INA, CFAI_HUMAN, FI, IF, KAF

Cross-references: UniProt · Ensembl · Human Protein Atlas · GeneCards · NCBI Gene

Protein identityUniProt · HPA

UniProt accession
P05156
Gene
CFI
Ensembl
ENSG00000205403
Chromosome
4
Canonical length
583 aa
Protein class
Disease related genes, Enzymes, Human disease related genes, Plasma proteins, Potential drug targets, Predicted secreted proteins
Secretome location
Secreted to blood

OverviewNCBI Gene

This gene encodes a serine proteinase that is essential for regulating the complement cascade. The encoded preproprotein is cleaved to produce both heavy and light chains, which are linked by disulfide bonds to form a heterodimeric glycoprotein. This heterodimer can cleave and inactivate the complement components C4b and C3b, and it prevents the assembly of the C3 and C5 convertase enzymes. Defects in this gene cause complement factor I deficiency, an autosomal recessive disease associated with a susceptibility to pyogenic infections. Mutations in this gene have been associated with a predisposition to atypical hemolytic uremic syndrome, a disease characterized by acute renal failure, microangiopathic hemolytic anemia and thrombocytopenia. Primary glomerulonephritis with immune deposits and age-related macular degeneration are other conditions associated with mutations of this gene. [provided by RefSeq, Dec 2015]

Canonical amino-acid sequenceUniProt

583 residues, UniProt reviewed canonical sequence.

>P05156|CFI
     1  MKLLHVFLLF LCFHLRFCKV TYTSQEDLVE KKCLAKKYTH LSCDKVFCQP WQRCIEGTCV
    61  CKLPYQCPKN GTAVCATNRR SFPTYCQQKS LECLHPGTKF LNNGTCTAEG KFSVSLKHGN
   121  TDSEGIVEVK LVDQDKTMFI CKSSWSMREA NVACLDLGFQ QGADTQRRFK LSDLSINSTE
   181  CLHVHCRGLE TSLAECTFTK RRTMGYQDFA DVVCYTQKAD SPMDDFFQCV NGKYISQMKA
   241  CDGINDCGDQ SDELCCKACQ GKGFHCKSGV CIPSQYQCNG EVDCITGEDE VGCAGFASVT
   301  QEETEILTAD MDAERRRIKS LLPKLSCGVK NRMHIRRKRI VGGKRAQLGD LPWQVAIKDA
   361  SGITCGGIYI GGCWILTAAH CLRASKTHRY QIWTTVVDWI HPDLKRIVIE YVDRIIFHEN
   421  YNAGTYQNDI ALIEMKKDGN KKDCELPRSI PACVPWSPYL FQPNDTCIVS GWGREKDNER
   481  VFSLQWGEVK LISNCSKFYG NRFYEKEMEC AGTYDGSIDA CKGDSGGPLV CMDANNVTYV
   541  WGVVSWGENC GKPEFPGVYT KVANYFDWIS YHVGRPFISQ YNV

LocalizationUniProt · AlphaFold · HPA

Whether an antibody against CFI can act on the native protein depends on physical access: surface and secreted proteins are reachable by circulating antibodies, intracellular proteins usually are not.

Antibody reachability
Secreted
Secreted
Yes
Transmembrane segments
0
Mean surface accessibility (rSASA)
0.27
Highest tissue expression
918 nTPM

Expression across tissuesHPA

Tissue

  • liver: 918 nTPM
  • kidney: 192 nTPM
  • epididymis: 58 nTPM
  • fallopian tube: 52 nTPM
  • gallbladder: 50 nTPM
  • adrenal gland: 49 nTPM

Single-cell type

  • hepatocytes: 50 nCPM
  • endometrial secretory cells: 21 nCPM
  • mesothelial cells: 21 nCPM
  • cholangiocytes: 16 nCPM
  • endometrial stromal cells: 16 nCPM
  • granulosa cells: 14 nCPM

Immune cell

  • basophil: 0 nTPM
  • classical monocyte: 0 nTPM
  • eosinophil: 0 nTPM
  • gdT-cell: 0 nTPM
  • intermediate monocyte: 0 nTPM
  • MAIT T-cell: 0 nTPM

Brain region

  • medulla oblongata: 13 nTPM
  • spinal cord: 6.2 nTPM
  • white matter: 5.5 nTPM
  • choroid plexus: 5 nTPM
  • midbrain: 4.3 nTPM
  • hypothalamus: 4.1 nTPM

DiseaseUniProt · ClinVar · IEDB · PubMed

Four sources answering four different questions about CFI.

Disease | AllUniProt

Conditions CFI is implicated in, by any mechanism.

  • Hemolytic uremic syndrome, atypical, 3 (AHUS3) MIM:612923
  • Complement factor I deficiency (CFI deficiency) MIM:610984
  • Macular degeneration, age-related, 13 (ARMD13) MIM:615439

Disease | GeneticClinVar

134 pathogenic / likely-pathogenic of 828 ClinVar records.

Conditions with pathogenic or likely-pathogenic variants.

Disease | ImmuneIEDB

Conditions an epitope on CFI was assayed in.

Genetic constraint and essentialitygnomAD · DepMap

Does the body need this protein intact? Low LOEUF or a strong DepMap dependency means loss or blockade of the protein is likely to be felt.

gnomAD LOEUF (loss-of-function intolerance)
0.76
gnomAD pLI
0
gnomAD missense Z
0.2
DepMap mean gene effect
0.1
DepMap dependency class
none

Cancer expressionTCGA

Across TCGA tumor cohorts, this protein is over-expressed in roughly 3% of surveyed tumor types (aggregate summary; per-cohort expression, alteration, and survival load in the interactive view).

OntologyGO

Biological processes

Molecular functions

Cellular components

Protein domainsUniProt · Pfam · InterPro

KeywordsUniProt

Antibody and autoantibody relevanceSeroatlas analysis

Seroatlas reads CFI as an antibody target. Whether an autoantibody or antibody against CFI could matter depends on whether native CFI is physically reachable, whether the body needs it intact, and whether it acts in a disease-relevant tissue.

CFI is annotated as secreted, so native CFI circulates and is directly accessible to antibodies. Secreted and cell-surface proteins are the autoantibody targets most likely to act like drugs, blocking or depleting the native protein.

Annotation status

The present source text does not explicitly label CFI as an autoantigen. Seroatlas presents hypothesis context only and does not manufacture a known-serology claim.

Canonical record: https://seroatlas.com/gene/CFI. Study-independent annotations aggregated from UniProt, Human Protein Atlas, PubMed, IEDB, Pfam, InterPro, Gene Ontology, AlphaFold, gnomAD, DepMap, ClinVar, TCGA. Catalog release seroatlas-reviewed-human-uniprot-20260313.

Seroatlas is the reference for exploring autoantibody and antibody serology at the human-protein level: the autoreactome and human serome, multiplex serology (HuProt, HuScan, VirScan, PhIP-Seq).

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