Complement C1q subcomponent subunit C (C1QC)
The protein contains 245 amino acids for an estimated molecular weight of 25774 Da.
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. (updated: Jan. 7, 2015)
Protein identification was indicated in the following studies:
- Goodman and co-workers. (2013) The proteomics and interactomics of human erythrocytes. Exp Biol Med (Maywood) 238(5), 509-518.
- Hegedűs and co-workers. (2015) Inconsistencies in the red blood cell membrane proteome analysis: generation of a database for research and diagnostic applications. Database (Oxford) 1-8.
- D'Alessandro and co-workers. (2017) Red blood cell proteomics update: is there more to discover? Blood Transfus. 15(2), 182-187.
Methods
The following articles were analysed to gather the proteome content of erythrocytes.
The gene or protein list provided in the studies were processed using the ID mapping API of Uniprot in September 2018. The number of proteins identified and mapped without ambiguity in these studies is indicated below.
Only Swiss-Prot entries (reviewed) were considered for protein evidence assignation.
| Publication | Identification 1 | Uniprot mapping 2 | Not mapped / Obsolete | TrEMBL | Swiss-Prot |
|---|---|---|---|---|---|
| Goodman (2013) | 2289 (gene list) | 2278 | 53 | 20599 | 2269 |
| Lange (2014) | 1234 | 1234 | 7 | 28 | 1224 |
| Hegedus (2015) | 2638 | 2622 | 0 | 235 | 2387 |
| Wilson (2016) | 1658 | 1528 | 170 | 291 | 1068 |
| d'Alessandro (2017) | 1826 | 1817 | 2 | 0 | 1815 |
| Bryk (2017) | 2090 | 2060 | 10 | 108 | 1942 |
| Chu (2018) | 1853 | 1804 | 55 | 362 | 1387 |
1 as available in the article and/or in supplementary material
2 uniprot mapping returns all protein isoforms as one entry
The compilation of older studies can be retrieved from the Red Blood Cell Collection database.
The data and differentiation stages presented below come from the proteomic study and analysis performed by our partners of the GReX consortium, more details are available in their published work.
(right-click above to access to more options from the contextual menu)
| Variant | Description |
|---|---|
| C1QD |
No binding partner found
Biological Process
Complement activation
Complement activation, classical pathway
Immune response
Innate immune response
Negative regulation of granulocyte differentiation
Negative regulation of macrophage differentiation
Regulation of complement activation
Synapse pruning
The reference OMIM entry for this protein is 120575
Complement component 1, q subcomponent, c chain; c1qc
Complement component c1q, c chain
Complement component 1, q subcomponent, gamma polypeptide; c1qg
CLONING
C1q, the first subcomponent of C1, has a complicated 18-chain structure: 6 A, 6 B, and 6 C chains. Each chain has a stretch of about 80 amino acids with the collagenous triplet Gly-X-Y where X and Y can include hydroxyproline and hydroxylysine. The A (120550), B (120570), and C chains combine to form 6 heteromeric triple helices in the collagenous regions of the chains (Sellar et al., 1991).GENE FUNCTION
Diebolder et al. (2014) found that specific noncovalent interactions between Fc segments of IgG antibodies resulted in the formation of ordered antibody hexamers after antigen binding on cells. These hexamers recruited and activated C1, the first component of complement, thereby triggering the complement cascade. The interactions between neighboring Fc segments could be manipulated to block, reconstitute, and enhance complement activation and killing of target cells, using all 4 human IgG subclasses. Diebolder et al. (2014) offered a general model for understanding antibody-mediated complement activation and the design of antibody therapeutics with enhanced efficacy.MAPPING
Sellar et al. (1991) found that the genes encoding the A, B, and C chains of human C1q are aligned, 5-prime to 3-prime, in the same orientation in the order A-C-B on a 24-kb stretch of DNA on chromosome 1p. A and C are separated by 4 kb and B and C are separated by 11 kb. Hybridization of cDNA probes to a hybrid cell line containing the derived X chromosome from an X;1(q21.2;p34) translocation described in a female patient with Duchenne muscular dystrophy (Lindenbaum et al., 1979; Boyd et al., 1988) showed that the A and B genes are located in the region 1p36.3-p34.1 (Sellar et al., 1992).GENE STRUCTURE
The A- (120550), B- (120570), and C-chain C1q genes are approximately 2.5, 2.6, and 3.2 kb long, respectively, and each contains 1 intron located within a codon for a glycine residue found halfway along the collagen-like region present in each chain. These glycine residues are located just before the point where the triple-helical portions of the C1q molecule appear to bend when viewed by electron microscopy. Southern blot analysis showed that there is only one gene per chain.MOLECULAR GENETICS
In patients with C1q deficiency (613652), Slingsby et al. (1996) identified homozygous mutations in the C1QC gene (120575.0001-120575.0003). ... More on the omim web site
Feb. 2, 2018: Protein entry updated
Automatic update: Uniprot description updated
Dec. 19, 2017: Protein entry updated
Automatic update: Uniprot description updated
Nov. 23, 2017: Protein entry updated
Automatic update: Uniprot description updated
March 25, 2017: Additional information
No protein expression data in P. Mayeux work for C1QC
March 16, 2016: Protein entry updated
Automatic update: OMIM entry 120575 was added.
Jan. 24, 2016: Protein entry updated
Automatic update: model status changed