FEATURES

DESCRIPTION

Also known as C1QA_HUMAN, C1QA. 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. 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).

EXTERNAL LINKS

C1QA

Complement C1q subcomponent subunit A

C1QA

Molecular Synopsis