C1qa
Function
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.
Post-translational modifications
O-linked glycans are Glc-Gal disaccharides typically found as secondary modifications of hydroxylated lysines in collagen-like domains.
Proline residues in the collagen-like domain motif, GXPG, are typically 4-hydroxylated.
Cellular localization
- Secreted
Alternative names
Complement C1q subcomponent subunit A, C1qa