This entry represents complement C1q subcomponent subunit A. C1q is a complex of nine proteins, six are disulfide-linked dimers of the A and B chains, and three are disulfide-linked dimers of the C chain []. C1q combines with C1r and C1s to form the first complement in the complement activation cascade, C1. C1qA contains an N-terminal collagen-like domain and a C-terminal C1q domain []. Complexes with C1r and C1s are formed via the collagen-like domain, whereas the C1q-like domain provides the means of interaction with C-reactive protein and IgG []. Deficiency of C1qA is associated with subacute cutaneous lupus erythematosus [].
