complement C1q

Function

• C1q associates with the proenzymes C1r & C1s to yield C1, the first component of the complement cascade
• the collagen-like regions of C1q interact with the Ca+2-dependent C1r(2)C1s(2) proenzyme complex, & 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

Structure

• C1q is composed of 9 subunits, 6 of which are disulfide- linked dimers of C1QA & C1QB, & 3 of which are disulfide- linked dimers of C1QC

More general terms

• complement
• molecular complex

Components

• complement C1q-gamma chain (complement C1q subunit C, C1QC)
• complement C1q-beta chain (complement C1q subunit B, C1QB)
• complement C1q-alpha chain (complement C1q subunit A, C1QA)

Database

• OMIM: https://mirror.omim.org/entry/120570