Immunoglobulin heavy constant gamma 2 (IGHG2)
The protein contains 326 amino acids for an estimated molecular weight of 35901 Da.
Constant region of immunoglobulin heavy chains. Immunoglobulins, also known as antibodies, are membrane-bound or secreted glycoproteins produced by B lymphocytes. In the recognition phase of humoral immunity, the membrane-bound immunoglobulins serve as receptors which, upon binding of a specific antigen, trigger the clonal expansion and differentiation of B lymphocytes into immunoglobulins-secreting plasma cells. Secreted immunoglobulins mediate the effector phase of humoral immunity, which results in the elimination of bound antigens (PubMed:22158414, PubMed:20176268). The antigen binding site is formed by the variable domain of one heavy chain, together with that of its associated light chain. Thus, each immunoglobulin has two antigen binding sites with remarkable affinity for a particular antigen. The variable domains are assembled by a process called V-(D)-J rearrangement and can then be subjected to somatic hypermutations which, after exposure to antigen and selection, allow affinity maturation for a particular antigen (PubMed:17576170, PubMed:20176268). (updated: Oct. 10, 2018)
Protein identification was indicated in the following studies:
- Bryk and co-workers. (2017) Quantitative Analysis of Human Red Blood Cell Proteome. J Proteome Res. 16(8), 2752-2761.
- 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.
This protein is annotated as membranous in UniProt.
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| Variant | Description |
|---|---|
| empty | |
| IMGT allele IGHG2*01 |
No binding partner found
Biological Process
B cell receptor signaling pathway
Complement activation
Complement activation, classical pathway
Defense response to bacterium
Fc-gamma receptor signaling pathway involved in phagocytosis
Innate immune response
Negative regulation of inflammatory response to antigenic stimulus
Opsonization
Peptide cross-linking
Phagocytosis, engulfment
Phagocytosis, recognition
Positive regulation of B cell activation
Regulation of complement activation
Cellular Component
Blood microparticle
External side of plasma membrane
Extracellular exosome
Extracellular region
Extracellular space
Immunoglobulin complex, circulating
Molecular Function
Antigen binding
Immunoglobulin receptor binding
Serine-type endopeptidase activity
The reference OMIM entry for this protein is 147110
Immunoglobulin heavy chain constant region gamma-2; ighg2
Immunoglobulin heavy chain gamma-2 constant region
Igg2 heavy chain constant region
Immunoglobulin gm2
DESCRIPTION
Immunoglobulins (Ig) are the antigen recognition molecules of B cells. An Ig molecule is made up of 2 identical heavy chains and 2 identical light chains (see 147200) joined by disulfide bonds so that each heavy chain is linked to a light chain and the 2 heavy chains are linked together. Each Ig heavy chain has an N-terminal variable (V) region containing the antigen-binding site and a C-terminal constant (C) region, encoded by an individual C region gene, that determines the isotype of the antibody and provides effector or signaling functions. The heavy chain V region is encoded by 1 each of 3 types of genes: V genes (see 147070), joining (J) genes (see 147010), and diversity (D) genes (see 146910). The C region genes are clustered downstream of the V region genes within the heavy chain locus on chromosome 14. There are 5 main Ig classes, including IgG, which is the most abundant. Human IgG can be subdivided into 4 subclasses that are numbered in order of their abundance in serum, with IgG1 (see IGHG1, 147100) being most abundant and IgG4 (see IGHG4, 147130) being least abundant. The IGHG2 gene encodes the C region of the gamma-2 heavy chain, which defines the IgG2 isotype. Naive B cells express the transmembrane forms of IgM (see IGHM, 147020) and IgD (see IGHD, 1471770) on their surface. During an antibody response, activated B cells can switch to the expression of individual downstream heavy chain C region genes, such as IGHG2, by a process of somatic recombination known as class switching. In addition, secreted Ig forms that act as antibodies can be produced by alternative RNA processing of the heavy chain C region sequences. The membrane forms of all Ig isotypes are monomeric, and all secreted IgG forms are also monomeric. IgG isotypes produced during an immune response are found in the bloodstream and in the extracellular spaces in tissues. Most IgG isotypes, including IgG2, can interact with complement component C1 (see 120550) to activate the classical complement pathway (summary by Murphy, 2012).CLONING
Connell et al. (1979) reported the amino acid sequences of most of 3 heavy chain C region domains, designated CH1 through CH3, of an IgG2 subclass protein obtained from a myeloma patient. They found that the CH1 domains of the gamma-1 (IGHG1; 147100) and gamma-2 chains were about 93% identical.MAPPING
The IGHG2 gene is located within the Ig heavy chain locus on chromosome 14q32 (Kirsch et al., 1982).MOLECULAR GENETICS
Oxelius et al. (1981) pointed out that deficiency of IgG2 in combination with IgA deficiency is a critical factor in whether or not IgA-deficient persons have illness (frequent infections, autoimmune disorders, atopy, malabsorption). No allotypes are known on gamma-4 or on gamma-2. The reason may be the test system. Anti-D antiserum is used and this antibody is usually gamma-1 or gamma-3. Patients with IgG2 deficiency have recurrent sinopulmonary infections caused by Pneumococcus and Hemophilus. Tashita et al. (1998) studied 2 Japanese brothers, ages 5 and 10 years, and found that both were homozygous for a 1-bp insertion in exon 4 of the IGHG2 gene (147110.0001), just upstream from the alternative splice site for M exons. The mutant membrane-bound gamma-2 heavy chain lost the transmembrane domain and the evolutionarily conserved cytoplasmic domain. Since several lines of evidence had indicated that intact expression of the membrane-bound heavy chain was e ... More on the omim web site
Oct. 20, 2018: Protein entry updated
Automatic update: OMIM entry 147110 was added.
Oct. 19, 2018: Additional information
Initial protein addition to the database. This entry was referenced in Bryk and co-workers. (2017).