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Protein

Complement C1q subcomponent subunit A

Gene

C1QA

Organism
Homo sapiens (Human)
Status
Reviewed-Annotation score: -Experimental evidence at protein leveli

Functioni

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.

GO - Molecular functioni

GO - Biological processi

Keywordsi

Biological processComplement pathway, Immunity, Innate immunity

Enzyme and pathway databases

ReactomeiR-HSA-166663 Initial triggering of complement
R-HSA-173623 Classical antibody-mediated complement activation
R-HSA-977606 Regulation of Complement cascade

Names & Taxonomyi

Protein namesi
Recommended name:
Complement C1q subcomponent subunit A
Gene namesi
Name:C1QA
OrganismiHomo sapiens (Human)
Taxonomic identifieri9606 [NCBI]
Taxonomic lineageiEukaryotaMetazoaChordataCraniataVertebrataEuteleostomiMammaliaEutheriaEuarchontogliresPrimatesHaplorrhiniCatarrhiniHominidaeHomo
Proteomesi
  • UP000005640 Componenti: Chromosome 1

Organism-specific databases

EuPathDBiHostDB:ENSG00000173372.16
HGNCiHGNC:1241 C1QA
MIMi120550 gene
neXtProtiNX_P02745

Subcellular locationi

Extracellular region or secreted Cytosol Plasma membrane Cytoskeleton Lysosome Endosome Peroxisome ER Golgi apparatus Nucleus Mitochondrion Manual annotation Automatic computational assertionGraphics by Christian Stolte; Source: COMPARTMENTS

Keywords - Cellular componenti

Secreted

Pathology & Biotechi

Involvement in diseasei

Complement component C1q deficiency (C1QD)
The disease is caused by mutations affecting the gene represented in this entry.
Disease descriptionA 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.
See also OMIM:613652

Organism-specific databases

DisGeNETi712
MalaCardsiC1QA
MIMi613652 phenotype
OpenTargetsiENSG00000173372
Orphaneti169147 Immunodeficiency due to an early component of complement deficiency
PharmGKBiPA25622

Chemistry databases

DrugBankiDB00054 Abciximab
DB00051 Adalimumab
DB00092 Alefacept
DB00087 Alemtuzumab
DB00074 Basiliximab
DB00112 Bevacizumab
DB00002 Cetuximab
DB00111 Daclizumab
DB00095 Efalizumab
DB00005 Etanercept
DB00056 Gemtuzumab ozogamicin
DB00078 Ibritumomab tiuxetan
DB00075 Muromonab
DB00108 Natalizumab
DB00110 Palivizumab
DB00073 Rituximab
DB00081 Tositumomab
DB00072 Trastuzumab

Polymorphism and mutation databases

BioMutaiC1QA
DMDMi399138

PTM / Processingi

Molecule processing

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Signal peptidei1 – 221 PublicationAdd BLAST22
ChainiPRO_000000351723 – 245Complement C1q subcomponent subunit AAdd BLAST223

Amino acid modifications

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Disulfide bondi26Interchain (with C-29 in B chain)
Modified residuei335-hydroxylysine1 Publication1
Glycosylationi33O-linked (Gal...) hydroxylysine1 Publication1
Modified residuei394-hydroxyproline1 Publication1
Modified residuei454-hydroxyproline1 Publication1
Modified residuei485-hydroxylysine1 Publication1
Glycosylationi48O-linked (Gal...) hydroxylysine1 Publication1
Modified residuei544-hydroxyproline1 Publication1
Modified residuei574-hydroxyproline1 Publication1
Modified residuei675-hydroxylysine1 Publication1
Glycosylationi67O-linked (Gal...) hydroxylysine1 Publication1
Modified residuei734-hydroxyproline1 Publication1
Modified residuei794-hydroxyproline1 Publication1
Modified residuei854-hydroxyproline1 Publication1
Modified residuei1005-hydroxylysine1 Publication1
Glycosylationi100O-linked (Gal...) hydroxylysine1 Publication1
Glycosylationi146N-linked (GlcNAc...) asparagine2 Publications1

Post-translational modificationi

O-linked glycans are assumed to be the Glc-Gal disaccharides typically found as secondary modifications of hydroxylated lysines in collagen-like domains.1 Publication

Keywords - PTMi

Disulfide bond, Glycoprotein, Hydroxylation

Proteomic databases

PaxDbiP02745
PeptideAtlasiP02745
PRIDEiP02745

PTM databases

iPTMnetiP02745

Expressioni

Gene expression databases

BgeeiENSG00000173372
CleanExiHS_C1QA
ExpressionAtlasiP02745 baseline and differential
GenevisibleiP02745 HS

Organism-specific databases

HPAiCAB009823
HPA002350

Interactioni

Subunit structurei

C1 is a calcium-dependent trimolecular complex of C1q, R and S 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.

Binary interactionsi

Show more details

Protein-protein interaction databases

BioGridi10717319 interactors.
CORUMiP02745
IntActiP02745 20 interactors.
MINTiP02745
STRINGi9606.ENSP00000363773

Structurei

Secondary structure

1245
Legend: HelixTurnBeta strandPDB Structure known for this area
Show more details
Feature keyPosition(s)DescriptionActionsGraphical viewLength
Beta strandi116 – 120Combined sources5
Beta strandi128 – 130Combined sources3
Beta strandi135 – 140Combined sources6
Turni146 – 148Combined sources3
Beta strandi150 – 152Combined sources3
Beta strandi157 – 169Combined sources13
Beta strandi171 – 179Combined sources9
Beta strandi182 – 184Combined sources3
Beta strandi188 – 191Combined sources4
Beta strandi195 – 197Combined sources3
Beta strandi199 – 209Combined sources11
Beta strandi214 – 224Combined sources11
Beta strandi229 – 232Combined sources4
Beta strandi235 – 243Combined sources9

3D structure databases

Select the link destinations:
PDBei
RCSB PDBi
PDBji
Links Updated
PDB entryMethodResolution (Å)ChainPositionsPDBsum
1PK6X-ray1.85A112-244[»]
2JG8X-ray2.05A/D112-245[»]
2JG9X-ray1.90A/D112-245[»]
2WNUX-ray2.30A/D112-245[»]
2WNVX-ray1.25A/D112-245[»]
5HKJX-ray1.35A110-245[»]
5HZFX-ray1.55A110-245[»]
6FCZelectron microscopy10.00A112-244[»]
ProteinModelPortaliP02745
SMRiP02745
ModBaseiSearch...
MobiDBiSearch...

Miscellaneous databases

EvolutionaryTraceiP02745

Family & Domainsi

Domains and Repeats

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Domaini31 – 109Collagen-likeAdd BLAST79
Domaini110 – 245C1qPROSITE-ProRule annotationAdd BLAST136

Keywords - Domaini

Collagen, Repeat, Signal

Phylogenomic databases

eggNOGiENOG410IK45 Eukaryota
ENOG410YJJD LUCA
GeneTreeiENSGT00900000140911
HOGENOMiHOG000085653
HOVERGENiHBG108220
InParanoidiP02745
KOiK03986
OMAiYYYFTFQ
OrthoDBiEOG091G0L3Y
PhylomeDBiP02745
TreeFamiTF329591

Family and domain databases

Gene3Di2.60.120.401 hit
InterProiView protein in InterPro
IPR001073 C1q_dom
IPR008160 Collagen
IPR037572 Complement_C1q_A
IPR008983 Tumour_necrosis_fac-like_dom
PANTHERiPTHR45066 PTHR45066, 1 hit
PfamiView protein in Pfam
PF00386 C1q, 1 hit
PF01391 Collagen, 1 hit
PRINTSiPR00007 COMPLEMNTC1Q
SMARTiView protein in SMART
SM00110 C1Q, 1 hit
SUPFAMiSSF49842 SSF49842, 1 hit
PROSITEiView protein in PROSITE
PS50871 C1Q, 1 hit

Sequencei

Sequence statusi: Complete.

Sequence processingi: The displayed sequence is further processed into a mature form.

P02745-1 [UniParc]FASTAAdd to basket

« Hide

        10         20         30         40         50
MEGPRGWLVL CVLAISLASM VTEDLCRAPD GKKGEAGRPG RRGRPGLKGE
60 70 80 90 100
QGEPGAPGIR TGIQGLKGDQ GEPGPSGNPG KVGYPGPSGP LGARGIPGIK
110 120 130 140 150
GTKGSPGNIK DQPRPAFSAI RRNPPMGGNV VIFDTVITNQ EEPYQNHSGR
160 170 180 190 200
FVCTVPGYYY FTFQVLSQWE ICLSIVSSSR GQVRRSLGFC DTTNKGLFQV
210 220 230 240
VSGGMVLQLQ QGDQVWVEKD PKKGHIYQGS EADSVFSGFL IFPSA
Length:245
Mass (Da):26,017
Last modified:July 1, 1993 - v2
Checksum:i8FF6B6AE02D49C4C
GO

Experimental Info

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Sequence conflicti97P → K AA sequence (PubMed:486087).Curated1
Sequence conflicti103K → P AA sequence (PubMed:486087).Curated1
Sequence conflicti172C → N AA sequence (PubMed:6981411).Curated1
Sequence conflicti178S → W AA sequence (PubMed:6981411).Curated1
Sequence conflicti240 – 243LIFP → ILPGF AA sequence (PubMed:6981411).Curated4

Natural variant

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Natural variantiVAR_02109023E → K1 PublicationCorresponds to variant dbSNP:rs17887074Ensembl.1

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
AF135157 mRNA Translation: AAD32626.1
AY789471 Genomic DNA Translation: AAV40828.1
AL158086 Genomic DNA Translation: CAI22892.1
AK311980 mRNA Translation: BAG34919.1
AL158086 Genomic DNA Translation: CAI22893.1
CH471134 Genomic DNA Translation: EAW95014.1
BC030153 mRNA Translation: AAH30153.1
BC071986 mRNA Translation: AAH71986.1
CCDSiCCDS226.1
PIRiS14350 C1HUQA
RefSeqiNP_001334394.1, NM_001347465.1
NP_001334395.1, NM_001347466.1
NP_057075.1, NM_015991.3
UniGeneiHs.632379

Genome annotation databases

EnsembliENST00000374642; ENSP00000363773; ENSG00000173372
ENST00000402322; ENSP00000385564; ENSG00000173372
GeneIDi712
KEGGihsa:712
UCSCiuc001bfy.4 human

Keywords - Coding sequence diversityi

Polymorphism

Similar proteinsi

Entry informationi

Entry nameiC1QA_HUMAN
AccessioniPrimary (citable) accession number: P02745
Secondary accession number(s): B2R4X2, Q5T963
Entry historyiIntegrated into UniProtKB/Swiss-Prot: July 21, 1986
Last sequence update: July 1, 1993
Last modified: April 25, 2018
This is version 194 of the entry and version 2 of the sequence. See complete history.
Entry statusiReviewed (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.

Miscellaneousi

Keywords - Technical termi

3D-structure, Complete proteome, Direct protein sequencing, Reference proteome