UniProt functional annotation for P02745



	UniProt functional annotation for P02745

UniProt code: P02745.

Organism: Homo sapiens (Human).

Taxonomy: Eukaryota; Metazoa; Chordata; Craniata; Vertebrata; Euteleostomi; Mammalia; Eutheria; Euarchontoglires; Primates; Haplorrhini; Catarrhini; Hominidae; Homo.

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 Ca(2+)-dependent C1r(2)C1s(2) 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: 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. Interacts (via C-terminus) with CD33; this interaction activates CD33 inhibitory motifs (PubMed:28325905). Interacts with CR1 (via Sushi 24 and Sushi 25 domains) (PubMed:29563915, PubMed:9324355). {ECO:0000269|PubMed:28325905, ECO:0000269|PubMed:29563915, ECO:0000269|PubMed:9324355}.

Subunit: (Microbial infection) Interacts with Staphylococcus aureus protein Cna; this interaction results in the inhibition of the classical complement pathway. {ECO:0000269|PubMed:23720782}.

Subcellular location: Secreted.

Ptm: O-linked glycans are assumed to be the Glc-Gal disaccharides typically found as secondary modifications of hydroxylated lysines in collagen-like domains. {ECO:0000269|PubMed:486087}.

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 variants affecting the gene represented in this entry.

Annotations taken from UniProtKB at the EBI.


Organism:		Homo sapiens (Human).
Taxonomy:		Eukaryota; Metazoa; Chordata; Craniata; Vertebrata; Euteleostomi; Mammalia; Eutheria; Euarchontoglires; Primates; Haplorrhini; Catarrhini; Hominidae; Homo.



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 Ca(2+)-dependent C1r(2)C1s(2) 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:		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. Interacts (via C-terminus) with CD33; this interaction activates CD33 inhibitory motifs (PubMed:28325905). Interacts with CR1 (via Sushi 24 and Sushi 25 domains) (PubMed:29563915, PubMed:9324355). {ECO:0000269\|PubMed:28325905, ECO:0000269\|PubMed:29563915, ECO:0000269\|PubMed:9324355}.
Subunit:		(Microbial infection) Interacts with Staphylococcus aureus protein Cna; this interaction results in the inhibition of the classical complement pathway. {ECO:0000269\|PubMed:23720782}.
Subcellular location:		Secreted.
Ptm:		O-linked glycans are assumed to be the Glc-Gal disaccharides typically found as secondary modifications of hydroxylated lysines in collagen-like domains. {ECO:0000269\|PubMed:486087}.
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 variants affecting the gene represented in this entry.