C1qB

Complement Component 1, q subcomponent (C1q) associates with C1r and C1s in order to yield the first component of the serum complement system. Deficiency of C1q has been associated with lupus erythematosus and glomerulonephritis. C1q is composed of 18 polypeptide chains: six A-chains, six B-chains, and six C-chains. Southern blot analysis of chromosomal DNA from vertebrate species demonstrated highest similarity between the C1qB genes, followed by C1qC and finally C1qA. Sequence comparison of C1q from three different species have shown that the B chains have the strongest similarity. C1q was already present at embryonic day 14 (E14) and showed little change in abundance through six weeks postnatal. At E16, C1qB mRNA was present at high abundance in putative microglia/macrophages in cortical marginal and intermediate zones, and hippocampal analge.

C1qB Related Areas

Enzyme>>Protease & Regulator>>Serine Protease & Regulator>>Complement System>>C1qB

Immunology>>Innate Immunity>>Complement System>>C1qB

C1qB Alternative Names

C1QB

Summaries for C1qB

Entrez Gene summary for C1qB:

This gene encodes a major constituent of the human complement subcomponent C1q. C1q associates with C1r and C1s in order to yield the first component of the serum complement system. Deficiency of C1q has been associated with lupus erythematosus and glomerulonephritis. C1q is composed of 18 polypeptide chains: six A-chains, six B-chains, and six C-chains. Each chain contains a collagen-like region located near the N terminus and a C-terminal globular region. The A-, B-, and C-chains are arranged in the order A-C-B on chromosome 1. This gene encodes the B-chain polypeptide of human complement subcomponent C1q

OMIM - description for C1qB:

Wikipedia summary for C1qB:

The C1q complex is potentially multivalent for attachment to the complement fixation sites of immunoglobulin. The sites are on the CH2 domain of IgG and, it is thought, on the CH4 domain of IgM. The appropriate peptide sequence of the complement fixing site might become exposed following complexing of the immunoglobulin, or the sites might always be available, but might require multiple attachment by C1q with critical geometry in order to achieve the necessary avidity.

Human C1qB Protein General Information

 

• Protein names: Recommended name: Complement C1q subcomponent subunit B
• Sequence length: 253 AA.
• Domain: Collagen Repeat Signal
• Sequence similarities: Contains 1 C1q domain. Contains 1 collagen-like domain.
• Post-translational modification: Hydroxylated on lysine and proline residues. Hydroxylated lysine residues can be glycosylated. Human C1Q contains up to 68.3 hydroxylysine-galactosylglucose residues and up to 2.5 hydroxylysine-galactose per molecule. Total percentage hydroxylysine residues glycosylated is 86.4%.
• Subunit structure: C1 is a calcium-dependent trimolecular complex of C1q, c1r and C1s 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.
• Subcellular location: Secreted.
• Involvement in disease: Defects in C1QB are a cause of complement component C1q deficiency (C1QD) [MIM:613652]. A rare defect resulting in C1 deficiency and impaired activation of the complement classical pathway. C1 deficiency generally leads to severe immune complex disease with features of systemic lupus erythematosus and glomerulonephritis.

General information above from UniProt

Function for C1qB Protein

UniProtKB:

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 Ca2+-dependent C1r2C1s2 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.

Genatlas:

• C1qB is classical pathway of C3 activation
• C1qB induces maturation of human dendritic cells (Csomor 2007)

Homology for human C1qB

• homolog to non collagen-like sequence of COLVIII and COLX

Phenotype Information for C1qB

• Gene/Locus: C1QB
• Phenotype: C1q deficiency

Phenotype Information for C1qB from OMIM (Online Mendelian Inheritance in Man)