Protein Domain : C1q domain IPR001073

Type	Domain
Description	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 [ ]. The C1qprotein is produced in collagen-producing cells and shows sequence and structural similarity to collagens VIII and X [, ]. 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 thetriple helix and for protein-protein recognition events [ ]. For collagen type X it has been suggested that the domain is important for initiation and maintenance of the correct assembly of the protein []. 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 β-sheets []. 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.
Short Name	C1q_dom