C1q γ-polypeptide deficiency

Gene Information


HUGO name: C1QC


  • C1QG
  • Complement component 1, q subcomponent, c polypeptide
  • Complement component 1, q subcomponent, gamma polypeptide
  • Complement C1q subcomponent, C chain precursor


Reference sequences

Chromosomal location


Protein Information


Protein 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.


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.

Post-translational modification:

O-linked glycans consist of glc-gal disaccharides.

Structures (PDB)


Collagen-like domain: 31-112

    C1q domain: 113-245

      Other features

      Signal peptide: 1-28

        Complement c1q subcomponent, c chain: 29-245

          Disulfide bond interchain (with other c chain): 32

            Other related resourses:


            Expression pattern for human

            Tissue Expression (%) Clones
            brain, pituitary 32.13 1:225
            thymus 16.10 1:449
            colon, 2 pooled adenocarcinomas 9.02 11:8815
            osteoarthritic cartilage 7.23 3:2999
            ovary (pool of 3) 6.60 4:4380
            mixed 4.43 37:60341
            human optic nerve 3.28 2:4406
            spleen 3.00 3:7229
            genitourinary tract 1.90 1:3813
            pool, liver+spleen 1.53 13:61327

            Animal models



            C. elegans