C1q domain (IPR001073)

Short name: C1q_dom

Overlapping homologous superfamilies

Domain relationships



This entry represents the C-terminal domain of C1q. C1q is a subunit of the C1 enzyme complex that activates the serum complement system. C1q comprises 6 A, 6 B and 6 C chains. These share the same topology, each possessing a small, globular N-terminal domain, a collagen-like Gly/Pro-rich central region, and a conserved C-terminal region, the C1q domain [PMID: 1706597]. The C1q protein is produced in collagen-producing cells and shows sequence and structural similarity to collagens VIII and X [PMID: 2591537, PMID: 2019595]. This domain is also found in multimerin and EMILIN proteins.

The C-terminal globular domain of the C1q subcomponents and collagen types VIII and X is important both for the correct folding and alignment of the triple helix and for protein-protein recognition events [PMID: 1867713]. For collagen type X it has been suggested that the domain is important for initiation and maintenance of the correct assembly of the protein [PMID: 1860888]. The globular head is a trimer of C1q domains. Each individual C1q adopts a 10-strand Jelly-roll fold arranged in two antiparallel 5-stranded beta-sheets [PMID: 22892318]. There are two well conserved regions within the C1q domain: an aromatic motif is located within the first half of the domain, the other conserved region is located near the C-terminal extremity.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.
PROSITE profiles