Skip Header

You are using a version of Internet Explorer that may not display all features of this website. Please upgrade to a modern browser.
Contribute Send feedback
Read comments (?) or add your own

P02746 (C1QB_HUMAN) Reviewed, UniProtKB/Swiss-Prot

Last modified April 16, 2014. Version 159. Feed History...

Clusters with 100%, 90%, 50% identity | Documents (6) | Third-party data text xml rdf/xml gff fasta
to top of pageNames·Attributes·General annotation·Ontologies·Interactions·Sequence annotation·Sequences·References·Web links·Cross-refs·Entry info·DocumentsCustomize order

Names and origin

Protein namesRecommended name:
Complement C1q subcomponent subunit B
Gene names
Name:C1QB
OrganismHomo sapiens (Human) [Reference proteome]
Taxonomic identifier9606 [NCBI]
Taxonomic lineageEukaryotaMetazoaChordataCraniataVertebrataEuteleostomiMammaliaEutheriaEuarchontogliresPrimatesHaplorrhiniCatarrhiniHominidaeHomo

Protein attributes

Sequence length253 AA.
Sequence statusComplete.
Sequence processingThe displayed sequence is further processed into a mature form.
Protein existenceEvidence at protein level

General annotation (Comments)

Function

C1q associates with the proenzymes C1r and C1s to yield C1, the first component of the serum complement system. The collagen-like regions of C1q interact with the Ca2+-dependent C1r2C1s2 proenzyme complex, and efficient activation of C1 takes place on interaction of the globular heads of C1q with the Fc regions of IgG or IgM antibody present in immune complexes.

Subunit structure

C1 is a calcium-dependent trimolecular complex of C1q, c1r and C1s in the molar ration of 1:2:2. C1q subcomponent is composed of nine subunits, six of which are disulfide-linked dimers of the A and B chains, and three of which are disulfide-linked dimers of the C chain. Ref.4

Subcellular location

Secreted.

Post-translational modification

Hydroxylated on lysine and proline residues. Hydroxylated lysine residues can be glycosylated. Human C1Q contains up to 68.3 hydroxylysine-galactosylglucose residues and up to 2.5 hydroxylysine-galactose per molecule. Total percentage hydroxylysine residues glycosylated is 86.4%. Ref.4 Ref.8

Involvement in disease

Complement component C1q deficiency (C1QD) [MIM:613652]: A disorder caused by impaired activation of the complement classical pathway. It generally leads to severe immune complex disease with features of systemic lupus erythematosus and glomerulonephritis.
Note: The disease is caused by mutations affecting the gene represented in this entry. Ref.11

Sequence similarities

Contains 1 C1q domain.

Contains 2 collagen-like domains.

Binary interactions

With

Entry

#Exp.

IntAct

Notes

C1QAP027454EBI-2813376,EBI-1220209

Sequence annotation (Features)

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifier

Molecule processing

Signal peptide1 – 2727 Ref.4 Ref.5
Chain28 – 253226Complement C1q subcomponent subunit B
PRO_0000003521

Regions

Domain37 – 8650Collagen-like 1
Domain60 – 11455Collagen-like 2
Domain117 – 253137C1q

Amino acid modifications

Modified residue281Pyrrolidone carboxylic acid
Disulfide bond31Interchain (with C-26 in chain A) Ref.4

Natural variations

Natural variant421G → D in C1QD. Ref.11
VAR_008541
Natural variant1231A → T in a breast cancer sample; somatic mutation. Ref.12
VAR_035551

Experimental info

Sequence conflict281Q → E AA sequence Ref.4
Sequence conflict851N → D AA sequence Ref.4
Sequence conflict1001G → P AA sequence Ref.4
Sequence conflict1001G → P AA sequence Ref.5

Secondary structure

....................... 253
Helix Strand Turn

Details...

Sequences

Sequence LengthMass (Da)Tools
P02746 [UniParc].

Last modified June 15, 2010. Version 3.
Checksum: D80C753C0D430EDC

FASTA25326,722
        10         20         30         40         50         60 
MMMKIPWGSI PVLMLLLLLG LIDISQAQLS CTGPPAIPGI PGIPGTPGPD GQPGTPGIKG 

        70         80         90        100        110        120 
EKGLPGLAGD HGEFGEKGDP GIPGNPGKVG PKGPMGPKGG PGAPGAPGPK GESGDYKATQ 

       130        140        150        160        170        180 
KIAFSATRTI NVPLRRDQTI RFDHVITNMN NNYEPRSGKF TCKVPGLYYF TYHASSRGNL 

       190        200        210        220        230        240 
CVNLMRGRER AQKVVTFCDY AYNTFQVTTG GMVLKLEQGE NVFLQATDKN SLLGMEGANS 

       250 
IFSGFLLFPD MEA 

« Hide

References

« Hide 'large scale' references
[1]"The DNA sequence and biological annotation of human chromosome 1."
Gregory S.G., Barlow K.F., McLay K.E., Kaul R., Swarbreck D., Dunham A., Scott C.E., Howe K.L., Woodfine K., Spencer C.C.A., Jones M.C., Gillson C., Searle S., Zhou Y., Kokocinski F., McDonald L., Evans R., Phillips K. expand/collapse author list , Atkinson A., Cooper R., Jones C., Hall R.E., Andrews T.D., Lloyd C., Ainscough R., Almeida J.P., Ambrose K.D., Anderson F., Andrew R.W., Ashwell R.I.S., Aubin K., Babbage A.K., Bagguley C.L., Bailey J., Beasley H., Bethel G., Bird C.P., Bray-Allen S., Brown J.Y., Brown A.J., Buckley D., Burton J., Bye J., Carder C., Chapman J.C., Clark S.Y., Clarke G., Clee C., Cobley V., Collier R.E., Corby N., Coville G.J., Davies J., Deadman R., Dunn M., Earthrowl M., Ellington A.G., Errington H., Frankish A., Frankland J., French L., Garner P., Garnett J., Gay L., Ghori M.R.J., Gibson R., Gilby L.M., Gillett W., Glithero R.J., Grafham D.V., Griffiths C., Griffiths-Jones S., Grocock R., Hammond S., Harrison E.S.I., Hart E., Haugen E., Heath P.D., Holmes S., Holt K., Howden P.J., Hunt A.R., Hunt S.E., Hunter G., Isherwood J., James R., Johnson C., Johnson D., Joy A., Kay M., Kershaw J.K., Kibukawa M., Kimberley A.M., King A., Knights A.J., Lad H., Laird G., Lawlor S., Leongamornlert D.A., Lloyd D.M., Loveland J., Lovell J., Lush M.J., Lyne R., Martin S., Mashreghi-Mohammadi M., Matthews L., Matthews N.S.W., McLaren S., Milne S., Mistry S., Moore M.J.F., Nickerson T., O'Dell C.N., Oliver K., Palmeiri A., Palmer S.A., Parker A., Patel D., Pearce A.V., Peck A.I., Pelan S., Phelps K., Phillimore B.J., Plumb R., Rajan J., Raymond C., Rouse G., Saenphimmachak C., Sehra H.K., Sheridan E., Shownkeen R., Sims S., Skuce C.D., Smith M., Steward C., Subramanian S., Sycamore N., Tracey A., Tromans A., Van Helmond Z., Wall M., Wallis J.M., White S., Whitehead S.L., Wilkinson J.E., Willey D.L., Williams H., Wilming L., Wray P.W., Wu Z., Coulson A., Vaudin M., Sulston J.E., Durbin R.M., Hubbard T., Wooster R., Dunham I., Carter N.P., McVean G., Ross M.T., Harrow J., Olson M.V., Beck S., Rogers J., Bentley D.R.
Nature 441:315-321(2006) [PubMed] [Europe PMC] [Abstract]
Cited for: NUCLEOTIDE SEQUENCE [LARGE SCALE GENOMIC DNA].
[2]"The status, quality, and expansion of the NIH full-length cDNA project: the Mammalian Gene Collection (MGC)."
The MGC Project Team
Genome Res. 14:2121-2127(2004) [PubMed] [Europe PMC] [Abstract]
Cited for: NUCLEOTIDE SEQUENCE [LARGE SCALE MRNA].
Tissue: Brain.
[3]"Molecular cloning and characterization of the complementary DNA and gene coding for the B-chain of subcomponent C1q of the human complement system."
Reid K.B.M.
Biochem. J. 231:729-735(1985) [PubMed] [Europe PMC] [Abstract]
Cited for: NUCLEOTIDE SEQUENCE [MRNA] OF 26-253.
[4]"Amino acid sequence of the N-terminal 108 amino acid residues of the B chain of subcomponent C1q of the first component of human complement."
Reid K.B.M., Thompson E.O.P.
Biochem. J. 173:863-868(1978) [PubMed] [Europe PMC] [Abstract]
Cited for: PROTEIN SEQUENCE OF 28-195, GLYCOSYLATION, PYROGLUTAMATE FORMATION AT GLU-28, DISULFIDE BOND, HYDROXYLATION.
[5]"Complete amino acid sequences of the three collagen-like regions present in subcomponent C1q of the first component of human complement."
Reid K.B.M.
Biochem. J. 179:367-371(1979) [PubMed] [Europe PMC] [Abstract]
Cited for: PROTEIN SEQUENCE OF 28-135.
[6]"Completion of the amino acid sequences of the A and B chains of subcomponent C1q of the first component of human complement."
Reid K.B.M., Gagnon J., Frampton J.
Biochem. J. 203:559-569(1982) [PubMed] [Europe PMC] [Abstract]
Cited for: PROTEIN SEQUENCE OF 136-253.
[7]"Cloning and characterization of the complementary DNA for the B chain of normal human serum C1q."
Reid K.B.M., Bentley D.R., Wood K.J.
Philos. Trans. R. Soc. Lond., B, Biol. Sci. 306:345-354(1984) [PubMed] [Europe PMC] [Abstract]
Cited for: NUCLEOTIDE SEQUENCE [MRNA] OF 226-253.
Tissue: Liver.
[8]"Comparable content of hydroxylysine-linked glycosides in subcomponents C1q of the first component of human, bovine and mouse complement."
Yonemasu K., Shinkai H., Sasaki T.
Coll. Relat. Res. 1:385-390(1981) [PubMed] [Europe PMC] [Abstract]
Cited for: GLYCOSYLATION ON HYDROXYLYSINES.
[9]"The crystal structure of the globular head of complement protein C1q provides a basis for its versatile recognition properties."
Gaboriaud C., Juanhuix J., Gruez A., Lacroix M., Darnault C., Pignol D., Verger D., Fontecilla-Camps J.-C., Arlaud G.J.
J. Biol. Chem. 278:46974-46982(2003) [PubMed] [Europe PMC] [Abstract]
Cited for: X-RAY CRYSTALLOGRAPHY (1.85 ANGSTROMS) OF 119-250.
[10]"Molecular basis of hereditary C1q deficiency."
Petry F.
Immunobiology 199:286-294(1998) [PubMed] [Europe PMC] [Abstract]
Cited for: REVIEW ON C1Q DEFICIENCY.
[11]"Molecular basis of a new type of C1q-deficiency associated with a non-functional low molecular weight (LMW) C1q: parallels and differences to other known genetic C1q-defects."
Petry F., Hauptmann G., Goetz J., Grosshans E., Loos M.
Immunopharmacology 38:189-201(1997) [PubMed] [Europe PMC] [Abstract]
Cited for: VARIANT C1QD ASP-42.
[12]"The consensus coding sequences of human breast and colorectal cancers."
Sjoeblom T., Jones S., Wood L.D., Parsons D.W., Lin J., Barber T.D., Mandelker D., Leary R.J., Ptak J., Silliman N., Szabo S., Buckhaults P., Farrell C., Meeh P., Markowitz S.D., Willis J., Dawson D., Willson J.K.V. expand/collapse author list , Gazdar A.F., Hartigan J., Wu L., Liu C., Parmigiani G., Park B.H., Bachman K.E., Papadopoulos N., Vogelstein B., Kinzler K.W., Velculescu V.E.
Science 314:268-274(2006) [PubMed] [Europe PMC] [Abstract]
Cited for: VARIANT [LARGE SCALE ANALYSIS] THR-123.
+Additional computationally mapped references.

Web resources

C1QBbase

C1QB mutation db

Cross-references

Sequence databases

EMBL
GenBank
DDBJ
AL158086 Genomic DNA. Translation: CAI22896.1.
BC008983 mRNA. Translation: AAH08983.1.
X03084 mRNA. Translation: CAA26880.1.
M36278 mRNA. Translation: AAC41692.1.
PIRC1HUQB. B23422.
RefSeqNP_000482.3. NM_000491.3.
XP_005246039.1. XM_005245982.1.
UniGeneHs.8986.

3D structure databases

PDBe
RCSB PDB
PDBj
EntryMethodResolution (Å)ChainPositionsPDBsum
1PK6X-ray1.85B119-250[»]
2JG8X-ray2.05B/E118-251[»]
2JG9X-ray1.90B/E118-251[»]
2WNUX-ray2.30B/E118-253[»]
2WNVX-ray1.25B/E118-253[»]
ProteinModelPortalP02746.
SMRP02746. Positions 41-114, 119-250.
ModBaseSearch...
MobiDBSearch...

Protein-protein interaction databases

BioGrid107174. 4 interactions.
IntActP02746. 7 interactions.
MINTMINT-6629999.
STRING9606.ENSP00000313967.

Chemistry

DrugBankDB00054. Abciximab.
DB00051. Adalimumab.
DB00092. Alefacept.
DB00087. Alemtuzumab.
DB00074. Basiliximab.
DB00112. Bevacizumab.
DB00002. Cetuximab.
DB00111. Daclizumab.
DB00095. Efalizumab.
DB00005. Etanercept.
DB00056. Gemtuzumab ozogamicin.
DB00078. Ibritumomab.
DB00028. Immune globulin.
DB00075. Muromonab.
DB00108. Natalizumab.
DB00110. Palivizumab.
DB00073. Rituximab.
DB00081. Tositumomab.
DB00072. Trastuzumab.

PTM databases

PhosphoSiteP02746.

Polymorphism databases

DMDM298286922.

Proteomic databases

PaxDbP02746.
PRIDEP02746.

Protocols and materials databases

DNASU713.
StructuralBiologyKnowledgebaseSearch...

Genome annotation databases

EnsemblENST00000314933; ENSP00000313967; ENSG00000173369.
GeneID713.
KEGGhsa:713.
UCSCuc001bgd.3. human.

Organism-specific databases

CTD713.
GeneCardsGC01P022979.
HGNCHGNC:1242. C1QB.
HPAHPA052116.
MIM120570. gene.
613652. phenotype.
neXtProtNX_P02746.
Orphanet169147. Immunodeficiency due to an early component of complement deficiency.
PharmGKBPA25623.
GenAtlasSearch...

Phylogenomic databases

eggNOGNOG115400.
HOGENOMHOG000085653.
HOVERGENHBG108220.
InParanoidP02746.
KOK03987.
OMAENRNYEP.
PhylomeDBP02746.
TreeFamTF329591.

Enzyme and pathway databases

ReactomeREACT_6900. Immune System.

Gene expression databases

ArrayExpressP02746.
BgeeP02746.
CleanExHS_C1QB.
GenevestigatorP02746.

Family and domain databases

Gene3D2.60.120.40. 1 hit.
InterProIPR001073. C1q.
IPR008160. Collagen.
IPR008983. Tumour_necrosis_fac-like_dom.
[Graphical view]
PfamPF00386. C1q. 1 hit.
PF01391. Collagen. 2 hits.
[Graphical view]
PRINTSPR00007. COMPLEMNTC1Q.
SMARTSM00110. C1Q. 1 hit.
[Graphical view]
SUPFAMSSF49842. SSF49842. 1 hit.
PROSITEPS50871. C1Q. 1 hit.
[Graphical view]
ProtoNetSearch...

Other

ChiTaRSC1QB. human.
EvolutionaryTraceP02746.
GenomeRNAi713.
NextBio2898.
PROP02746.
SOURCESearch...

Entry information

Entry nameC1QB_HUMAN
AccessionPrimary (citable) accession number: P02746
Secondary accession number(s): Q5T959, Q96H17
Entry history
Integrated into UniProtKB/Swiss-Prot: July 21, 1986
Last sequence update: June 15, 2010
Last modified: April 16, 2014
This is version 159 of the entry and version 3 of the sequence. [Complete history]
Entry statusReviewed (UniProtKB/Swiss-Prot)
Annotation programChordata Protein Annotation Program
DisclaimerAny medical or genetic information present in this entry is provided for research, educational and informational purposes only. It is not in any way intended to be used as a substitute for professional medical advice, diagnosis, treatment or care.

Relevant documents

SIMILARITY comments

Index of protein domains and families

PDB cross-references

Index of Protein Data Bank (PDB) cross-references

MIM cross-references

Online Mendelian Inheritance in Man (MIM) cross-references in UniProtKB/Swiss-Prot

Human polymorphisms and disease mutations

Index of human polymorphisms and disease mutations

Human entries with polymorphisms or disease mutations

List of human entries with polymorphisms or disease mutations

Human chromosome 1

Human chromosome 1: entries, gene names and cross-references to MIM