Seroatlas · Human Serome Atlas

C4BPA

C4b-binding protein alpha chain

Also known as: C4BP, C4BPA_HUMAN

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

Protein identityUniProt · HPA

UniProt accession
P04003
Gene
C4BPA
Ensembl
ENSG00000123838
Chromosome
1
Canonical length
597 aa
Protein class
Human disease related genes, Plasma proteins, Predicted secreted proteins
Secretome location
Secreted to blood
Quaternary structure
Homoheptamer

OverviewNCBI Gene

This gene encodes a member of a superfamily of proteins composed predominantly of tandemly arrayed short consensus repeats of approximately 60 amino acids. Along with a single, unique beta-chain, seven identical alpha-chains encoded by this gene assemble into the predominant isoform of C4b-binding protein, a multimeric protein that controls activation of the complement cascade through the classical pathway. The genes encoding both alpha and beta chains are located adjacent to each other on human chromosome 1 in the regulator of complement activation gene cluster. Two pseudogenes of this gene are also found in the cluster. [provided by RefSeq, Jul 2008]

Canonical amino-acid sequenceUniProt

597 residues, UniProt reviewed canonical sequence.

>P04003|C4BPA
     1  MHPPKTPSGA LHRKRKMAAW PFSRLWKVSD PILFQMTLIA ALLPAVLGNC GPPPTLSFAA
    61  PMDITLTETR FKTGTTLKYT CLPGYVRSHS TQTLTCNSDG EWVYNTFCIY KRCRHPGELR
   121  NGQVEIKTDL SFGSQIEFSC SEGFFLIGST TSRCEVQDRG VGWSHPLPQC EIVKCKPPPD
   181  IRNGRHSGEE NFYAYGFSVT YSCDPRFSLL GHASISCTVE NETIGVWRPS PPTCEKITCR
   241  KPDVSHGEMV SGFGPIYNYK DTIVFKCQKG FVLRGSSVIH CDADSKWNPS PPACEPNSCI
   301  NLPDIPHASW ETYPRPTKED VYVVGTVLRY RCHPGYKPTT DEPTTVICQK NLRWTPYQGC
   361  EALCCPEPKL NNGEITQHRK SRPANHCVYF YGDEISFSCH ETSRFSAICQ GDGTWSPRTP
   421  SCGDICNFPP KIAHGHYKQS SSYSFFKEEI IYECDKGYIL VGQAKLSCSY SHWSAPAPQC
   481  KALCRKPELV NGRLSVDKDQ YVEPENVTIQ CDSGYGVVGP QSITCSGNRT WYPEVPKCEW
   541  ETPEGCEQVL TGKRLMQCLP NPEDVKMALE VYKLSLEIEQ LELQRDSARQ STLDKEL

LocalizationUniProt · AlphaFold · HPA

Whether an antibody against C4BPA 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)
0.39
Highest tissue expression
1,793 nTPM

Expression across tissuesHPA

Tissue

  • liver: 1,793 nTPM
  • lung: 163 nTPM
  • pancreas: 9.3 nTPM
  • cervix: 5.9 nTPM
  • breast: 4.2 nTPM
  • endometrium: 4.2 nTPM

Single-cell type

  • hepatocytes: 1,057 nCPM
  • alveolar cells type 2: 397 nCPM
  • transitional alveolar cells: 240 nCPM
  • alveolar cells type 1: 196 nCPM
  • endometrial glandular cells: 95 nCPM
  • neutrophils: 54 nCPM

Immune cell

  • neutrophil: 30 nTPM
  • non-classical monocyte: 0.2 nTPM
  • classical monocyte: 0.1 nTPM
  • basophil: 0 nTPM
  • eosinophil: 0 nTPM
  • gdT-cell: 0 nTPM

Brain region

  • cerebellum: 2.6 nTPM
  • hypothalamus: 2.6 nTPM
  • pons: 2.1 nTPM
  • basal ganglia: 1.9 nTPM
  • white matter: 1.9 nTPM
  • medulla oblongata: 1.7 nTPM

DiseaseUniProt · ClinVar · IEDB · PubMed

Four sources answering four different questions about C4BPA.

Disease | ImmuneIEDB

Conditions an epitope on C4BPA 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)
0.43
gnomAD pLI
0.46
gnomAD missense Z
1.6
DepMap mean gene effect
0.02
DepMap dependency class
selective

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 C4BPA as an antibody target. Whether an autoantibody or antibody against C4BPA could matter depends on whether native C4BPA is physically reachable, whether the body needs it intact, and whether it acts in a disease-relevant tissue.

C4BPA is annotated as secreted, so native C4BPA 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 C4BPA as an autoantigen. Seroatlas presents hypothesis context only and does not manufacture a known-serology claim.

Canonical record: https://seroatlas.com/gene/C4BPA. 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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