C1q

A subcomponent of complement C1, composed of six copies of three polypeptide chains (A, B, and C), each encoded by a separate gene (C1QA; C1QB; C1QC). This complex is arranged in nine subunits (six disulfide-linked dimers of A and B, and three disulfide-linked homodimers of C). C1q has binding sites for antibodies (the heavy chain of IMMUNOGLOBULIN G or IMMUNOGLOBULIN M). The interaction of C1q and immunoglobulin activates the two proenzymes COMPLEMENT C1R and COMPLEMENT C1S, thus initiating the cascade of COMPLEMENT ACTIVATION via the CLASSICAL COMPLEMENT PATHWAY. (mesh:D015922)

Cross-references

• SCOMP:C0016
• MESH:D015922 - Complement C1q
• BEL:C1q Complex

Synonyms

Synonym	Reference	Specificity
C1q		Exact

Incoming Relations

Identifier	Name	Relation
HGNC:1241	C1QA	partof
HGNC:1242	C1QB	partof

Outgoing Relations

None available.