Complement C1q subcomponent subunit B (C1QB)
The protein contains 253 amino acids for an estimated molecular weight of 26722 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.
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| Variant | Description |
|---|---|
| C1QD | |
| a breast cancer sample |
Biological Process
Complement activation
Complement activation, classical pathway
Innate immune response
Inner ear development
Regulation of complement activation
Synapse pruning
The reference OMIM entry for this protein is 120570
Complement component 1, q subcomponent, b chain; c1qb
Complement component 1, q subcomponent, beta polypeptide
Complement component c1q, b chain
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, and C (120575) chains combine to form 6 heteromeric triple helices in the collagenous regions of the chains (Sellar et al., 1991).MAPPING
Using a cDNA probe to the B chain of C1q, Solomon et al. (1985) assigned the gene to chromosome 1 in somatic cell hybrids. A hybrid containing 1p, but no 1q, allowed them to localize the gene to 1p. The genes for the A, B, and C chains of C1q are tandemly arranged 5-prime to 3-prime in the order A-C-B on a 24-kb stretch of DNA (Sellar et al., 1991). 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 FUNCTION
Querec et al. (2009) noted that a major challenge of vaccinology is to prospectively determine efficacy. They applied a systems biology approach, including multiplex cytokine analysis, flow cytometry, and microarray transcriptional profiling, to identify early gene signatures predicting immune responses in humans immunized with YF-17D, the well-established and successful vaccine for yellow fever. Computational analysis identified a gene signature that included C1QB and EIF2AK4 (609280), a part of the integrated stress response, that correlated with and predicted CD8 (see 186910)-positive T-cell responses to the vaccine. Neutralizing antibody responses completely correlated with induction of TNFRSF17 (109545), the B-cell maturation factor. Querec et al. (2009) concluded that systems biology approaches can identify correlates of innate immunity and subsequent adaptive immune responses. 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.MOLECULAR GENETICS
The first molecular lesion in C1q deficiency (613652) was reported by McAdam et al. (1988). A homozygous G-to-A transition at nucleotide 150 in the B-chain (120570.0001) resulted in a premature stop codon. The patient had no antigenetically detectable C1q. ... 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
June 20, 2017: Protein entry updated
Automatic update: comparative model was added.
March 25, 2017: Additional information
No protein expression data in P. Mayeux work for C1QB
March 16, 2016: Protein entry updated
Automatic update: OMIM entry 120570 was added.
Jan. 24, 2016: Protein entry updated
Automatic update: model status changed