P02745 (C1QA_HUMAN) Reviewed, UniProtKB/Swiss-Prot

Names and origin

Protein names

Recommended name:
Complement C1q subcomponent subunit A

Gene names

Name:

C1QA

Organism

Homo sapiens (Human) [Reference proteome]

Taxonomic identifier

9606 [NCBI]

Taxonomic lineage

cellular organisms › Eukaryota › Opisthokonta › Metazoa › Eumetazoa › Bilateria › Deuterostomia › Chordata › Craniata › Vertebrata › Gnathostomata › Teleostomi › Euteleostomi › Sarcopterygii › Tetrapoda › Amniota › Mammalia › Theria › Eutheria › Euarchontoglires › Primates › Haplorrhini › Simiiformes › Catarrhini › Hominoidea › Hominidae › Homininae › Homo

Protein attributes

Sequence length	245 AA.
Sequence status	Complete.
Sequence processing	The displayed sequence is further processed into a mature form.
Protein existence	Evidence 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, 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.
Subcellular location	Secreted.
Post-translational modification	O-linked glycans consist of Glc-Gal disaccharides bound to the oxygen atom of post-translationally added hydroxyl groups.
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.
Sequence similarities	Contains 1 C1q domain. Contains 1 collagen-like domain.

Ontologies

Keywords
Biological process	Complement pathway Immunity Innate immunity
Cellular component	Secreted
Coding sequence diversity	Polymorphism
Domain	Collagen Repeat Signal
PTM	Disulfide bond Glycoprotein Hydroxylation
Technical term	3D-structure Complete proteome Direct protein sequencing Reference proteome
Gene Ontology (GO)
Biological_process	cell-cell signaling Traceable author statement PubMed 9461517. Source: ProtInc complement activation, classical pathway Traceable author statement. Source: Reactome innate immune response Traceable author statement. Source: Reactome
Cellular_component	collagen Inferred from electronic annotation. Source: UniProtKB-KW complement component C1 complex Traceable author statement PubMed 9461517. Source: ProtInc
Complete GO annotation...

Binary interactions

With	Entry	#Exp.	IntAct	Notes
C1QB	P02746	3	EBI-1220209,EBI-2813376

Sequence annotation (Features)

Feature key

Position(s)

Length

Description

Graphical view

Feature identifier

Molecule processing

Signal peptide

1 – 22

22

Ref.8

Chain

23 – 245

223

Complement C1q subcomponent subunit A

PRO_0000003517

Regions

Domain

31 – 109

79

Collagen-like

Domain

110 – 245

136

C1q

Amino acid modifications

Modified residue

33

1

5-hydroxylysine

Modified residue

39

1

4-hydroxyproline

Modified residue

45

1

4-hydroxyproline

Modified residue

48

1

5-hydroxylysine

Modified residue

54

1

4-hydroxyproline

Modified residue

57

1

4-hydroxyproline

Modified residue

67

1

5-hydroxylysine

Modified residue

73

1

4-hydroxyproline

Modified residue

85

1

4-hydroxyproline

Modified residue

97

1

4-hydroxyproline

Modified residue

100

1

5-hydroxylysine

Modified residue

103

1

5-hydroxylysine

Glycosylation

33

1

O-linked (Gal...)

Glycosylation

48

1

O-linked (Gal...)

Glycosylation

67

1

O-linked (Gal...)

Glycosylation

100

1

O-linked (Gal...)

Glycosylation

103

1

O-linked (Gal...)

Glycosylation

146

1

N-linked (GlcNAc...) Ref.10 Ref.11

Disulfide bond

26

Interchain (with C-29 in B chain)

Natural variations

Natural variant

23

1

E → K. Ref.3
Corresponds to variant rs17887074 [ dbSNP | Ensembl ].

VAR_021090

Experimental info

Sequence conflict

97

1

P → K AA sequence Ref.8

Sequence conflict

103

1

K → P AA sequence Ref.8

Sequence conflict

172

1

C → N AA sequence Ref.9

Sequence conflict

178

1

S → W AA sequence Ref.9

Sequence conflict

240 – 243

4

LIFP → ILPGF AA sequence Ref.9

Secondary structure

1

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

245

Helix Strand Turn

Details...

Beta strand

116 – 120

5

Beta strand

128 – 131

4

Beta strand

135 – 140

6

Turn

146 – 148

3

Beta strand

150 – 152

3

Beta strand

157 – 169

13

Beta strand

171 – 179

9

Beta strand

182 – 184

3

Beta strand

188 – 191

4

Beta strand

195 – 197

3

Beta strand

199 – 209

11

Beta strand

214 – 224

11

Beta strand

229 – 232

4

Beta strand

235 – 243

9

Sequences

	Sequence		Length	Mass (Da)
	P02745 [UniParc]. Last modified July 1, 1993. Version 2. Checksum: 8FF6B6AE02D49C4C	FASTA	245	26,017
	10 20 30 40 50 60 MEGPRGWLVL CVLAISLASM VTEDLCRAPD GKKGEAGRPG RRGRPGLKGE QGEPGAPGIR 70 80 90 100 110 120 TGIQGLKGDQ GEPGPSGNPG KVGYPGPSGP LGARGIPGIK GTKGSPGNIK DQPRPAFSAI 130 140 150 160 170 180 RRNPPMGGNV VIFDTVITNQ EEPYQNHSGR FVCTVPGYYY FTFQVLSQWE ICLSIVSSSR 190 200 210 220 230 240 GQVRRSLGFC DTTNKGLFQV VSGGMVLQLQ QGDQVWVEKD PKKGHIYQGS EADSVFSGFL IFPSA

References

	« Hide 'large scale' referencesShow 'large scale' references »
[1]	"Characterization and organization of the genes encoding the A-, B- and C-chains of human complement subcomponent C1q. The complete derived amino acid sequence of human C1q." Sellar G.C., Blake D.J., Reid K.B.M. Biochem. J. 274:481-490(1991) [PubMed] [Europe PMC] [Abstract] Cited for: NUCLEOTIDE SEQUENCE [GENOMIC DNA]. Tissue: Monocyte.
[2]	Wan T., Zhang W., Cao X. Submitted (MAR-1999) to the EMBL/GenBank/DDBJ databases Cited for: NUCLEOTIDE SEQUENCE [MRNA].
[3]	SeattleSNPs variation discovery resource Submitted (OCT-2004) to the EMBL/GenBank/DDBJ databases Cited for: NUCLEOTIDE SEQUENCE [GENOMIC DNA], VARIANT LYS-23.
[4]	"Complete sequencing and characterization of 21,243 full-length human cDNAs." Ota T., Suzuki Y., Nishikawa T., Otsuki T., Sugiyama T., Irie R., Wakamatsu A., Hayashi K., Sato H., Nagai K., Kimura K., Makita H., Sekine M., Obayashi M., Nishi T., Shibahara T., Tanaka T., Ishii S. , Yamamoto J., Saito K., Kawai Y., Isono Y., Nakamura Y., Nagahari K., Murakami K., Yasuda T., Iwayanagi T., Wagatsuma M., Shiratori A., Sudo H., Hosoiri T., Kaku Y., Kodaira H., Kondo H., Sugawara M., Takahashi M., Kanda K., Yokoi T., Furuya T., Kikkawa E., Omura Y., Abe K., Kamihara K., Katsuta N., Sato K., Tanikawa M., Yamazaki M., Ninomiya K., Ishibashi T., Yamashita H., Murakawa K., Fujimori K., Tanai H., Kimata M., Watanabe M., Hiraoka S., Chiba Y., Ishida S., Ono Y., Takiguchi S., Watanabe S., Yosida M., Hotuta T., Kusano J., Kanehori K., Takahashi-Fujii A., Hara H., Tanase T.-O., Nomura Y., Togiya S., Komai F., Hara R., Takeuchi K., Arita M., Imose N., Musashino K., Yuuki H., Oshima A., Sasaki N., Aotsuka S., Yoshikawa Y., Matsunawa H., Ichihara T., Shiohata N., Sano S., Moriya S., Momiyama H., Satoh N., Takami S., Terashima Y., Suzuki O., Nakagawa S., Senoh A., Mizoguchi H., Goto Y., Shimizu F., Wakebe H., Hishigaki H., Watanabe T., Sugiyama A., Takemoto M., Kawakami B., Yamazaki M., Watanabe K., Kumagai A., Itakura S., Fukuzumi Y., Fujimori Y., Komiyama M., Tashiro H., Tanigami A., Fujiwara T., Ono T., Yamada K., Fujii Y., Ozaki K., Hirao M., Ohmori Y., Kawabata A., Hikiji T., Kobatake N., Inagaki H., Ikema Y., Okamoto S., Okitani R., Kawakami T., Noguchi S., Itoh T., Shigeta K., Senba T., Matsumura K., Nakajima Y., Mizuno T., Morinaga M., Sasaki M., Togashi T., Oyama M., Hata H., Watanabe M., Komatsu T., Mizushima-Sugano J., Satoh T., Shirai Y., Takahashi Y., Nakagawa K., Okumura K., Nagase T., Nomura N., Kikuchi H., Masuho Y., Yamashita R., Nakai K., Yada T., Nakamura Y., Ohara O., Isogai T., Sugano S. Nat. Genet. 36:40-45(2004) [PubMed] [Europe PMC] [Abstract] Cited for: NUCLEOTIDE SEQUENCE [LARGE SCALE MRNA]. Tissue: Spleen.
[5]	"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. , 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].
[6]	Mural R.J., Istrail S., Sutton G.G., Florea L., Halpern A.L., Mobarry C.M., Lippert R., Walenz B., Shatkay H., Dew I., Miller J.R., Flanigan M.J., Edwards N.J., Bolanos R., Fasulo D., Halldorsson B.V., Hannenhalli S., Turner R. , Yooseph S., Lu F., Nusskern D.R., Shue B.C., Zheng X.H., Zhong F., Delcher A.L., Huson D.H., Kravitz S.A., Mouchard L., Reinert K., Remington K.A., Clark A.G., Waterman M.S., Eichler E.E., Adams M.D., Hunkapiller M.W., Myers E.W., Venter J.C. Submitted (JUL-2005) to the EMBL/GenBank/DDBJ databases Cited for: NUCLEOTIDE SEQUENCE [LARGE SCALE GENOMIC DNA].
[7]	"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: Spleen.
[8]	"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 23-130.
[9]	"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 131-245.
[10]	"Human plasma N-glycoproteome analysis by immunoaffinity subtraction, hydrazide chemistry, and mass spectrometry." Liu T., Qian W.-J., Gritsenko M.A., Camp D.G. II, Monroe M.E., Moore R.J., Smith R.D. J. Proteome Res. 4:2070-2080(2005) [PubMed] [Europe PMC] [Abstract] Cited for: GLYCOSYLATION [LARGE SCALE ANALYSIS] AT ASN-146, MASS SPECTROMETRY. Tissue: Plasma.
[11]	"Glycoproteomics analysis of human liver tissue by combination of multiple enzyme digestion and hydrazide chemistry." Chen R., Jiang X., Sun D., Han G., Wang F., Ye M., Wang L., Zou H. J. Proteome Res. 8:651-661(2009) [PubMed] [Europe PMC] [Abstract] Cited for: GLYCOSYLATION [LARGE SCALE ANALYSIS] AT ASN-146, MASS SPECTROMETRY. Tissue: Liver.
[12]	"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 112-244.
[13]	"Molecular basis of hereditary C1q deficiency." Petry F. Immunobiology 199:286-294(1998) [PubMed] [Europe PMC] [Abstract] Cited for: REVIEW ON C1Q DEFICIENCY.
+	Additional computationally mapped references.

Web resources

C1QAbase

C1QA mutation db

SeattleSNPs

Cross-references

Sequence databases

EMBL
GenBank
DDBJ

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.

IPI

IPI00022392.

PIR

C1HUQA. S14350.

RefSeq

NP_057075.1. NM_015991.2.

UniGene

Hs.632379.

3D structure databases

PDBe
RCSB PDB
PDBj

Entry	Method	Resolution (Å)	Chain	Positions	PDBsum
1PK6	X-ray	1.85	A	112-244	[»]
2JG8	X-ray	2.05	A/D	112-245	[»]
2JG9	X-ray	1.90	A/D	112-245	[»]
2WNU	X-ray	2.30	A/D	112-245	[»]
2WNV	X-ray	1.25	A/D	112-245	[»]

ProteinModelPortal

P02745.

ModBase

Search...

Protein-protein interaction databases

IntAct

P02745. 13 interactions.

MINT

MINT-1195525.

STRING

9606.ENSP00000363773.

Polymorphism databases

DMDM

399138.

Proteomic databases

PaxDb

P02745.

PeptideAtlas

P02745.

PRIDE

P02745.

Protocols and materials databases

DNASU

712.

StructuralBiologyKnowledgebase

Search...

Genome annotation databases

Ensembl

ENST00000374642; ENSP00000363773; ENSG00000173372.
ENST00000402322; ENSP00000385564; ENSG00000173372.
ENST00000438241; ENSP00000416841; ENSG00000173372.

GeneID

712.

KEGG

hsa:712.

UCSC

uc001bfy.3. human.

Organism-specific databases

CTD

712.

GeneCards

GC01P022962.

HGNC

HGNC:1241. C1QA.

HPA

CAB009823.
HPA002350.

MIM

120550. gene.
613652. phenotype.

neXtProt

NX_P02745.

Orphanet

169147. Immunodeficiency due to an early component of complement deficiency.

PharmGKB

PA25622.

GenAtlas

Search...

Phylogenomic databases

eggNOG

NOG126311.

HOGENOM

HOG000085653.

HOVERGEN

HBG108220.

KO

K03986.

OrthoDB

EOG473PS4.

Enzyme and pathway databases

Reactome

REACT_6900. Immune System.

Gene expression databases

Bgee

P02745.

CleanEx

HS_C1QA.

Genevestigator

P02745.

GermOnline

ENSG00000173372. Homo sapiens.

Family and domain databases

Gene3D

2.60.120.40. 1 hit.

InterPro

IPR001073. C1q.
IPR008160. Collagen.
IPR008983. Tumour_necrosis_fac-like_dom.
[Graphical view]

Pfam

PF00386. C1q. 1 hit.
PF01391. Collagen. 1 hit.
[Graphical view]

PRINTS

PR00007. COMPLEMNTC1Q.

SMART

SM00110. C1Q. 1 hit.
[Graphical view]

SUPFAM

SSF49842. TNF_like. 1 hit.

PROSITE

PS50871. C1Q. 1 hit.
[Graphical view]

ProtoNet

Search...

Other

ChiTaRS

C1QA. human.

DrugBank

DB00054. 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.

EvolutionaryTrace

P02745.

GenomeRNAi

712.

NextBio

2894.

SOURCE

Search...

Entry information

Entry name

C1QA_HUMAN

Accession

Primary (citable) accession number: P02745
Secondary accession number(s): B2R4X2, Q5T963

Entry history

Integrated into UniProtKB/Swiss-Prot:	July 21, 1986
Last sequence update:	July 1, 1993
Last modified:	May 1, 2013
This is version 149 of the entry and version 2 of the sequence. [Complete history]

Entry status

Reviewed (UniProtKB/Swiss-Prot)

Annotation program

Chordata Protein Annotation Program

Disclaimer

Any 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.