Immunoglobulin heavy constant alpha 1 (IGHA1)

The protein contains 353 amino acids for an estimated molecular weight of 37655 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). Ig alpha is the major immunoglobulin class in body secretions (PubMed:2241915). (updated: Oct. 10, 2018)

Protein identification was indicated in the following studies:

  1. Bryk and co-workers. (2017) Quantitative Analysis of Human Red Blood Cell Proteome. J Proteome Res. 16(8), 2752-2761.
  2. 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.

PublicationIdentification 1Uniprot mapping 2Not mapped /
Obsolete
TrEMBLSwiss-Prot
Goodman (2013)2289 (gene list)227853205992269
Lange (2014)123412347281224
Hegedus (2015)2638262202352387
Wilson (2016)165815281702911068
d'Alessandro (2017)18261817201815
Bryk (2017)20902060101081942
Chu (2018)18531804553621387

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.

No sequence conservation computed yet.

This protein is annotated as membranous in UniProt.


Interpro domains
Total structural coverage: 61%
Model score: 100
No model available.

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VariantDescription
dbSNP:rs1407

No binding partner found

The reference OMIM entry for this protein is 146900

Iga constant heavy chain 1; igha1
Immunoglobulin am1

IgA is the predominant immunoglobulin class in body secretions, such as saliva, tears, bronchial secretions, nasal mucosal secretions, prostatic fluid, vaginal secretions, and mucous secretions of the small intestines. It may serve both to defend against local infection and to prevent access of foreign antigens to the general immunologic system. Absence of certain immunoglobulins in patients with deleted chromosome 18 suggests the localization of structural and/or controller genes to that chromosome (Finley et al., 1968). Vyas and Fudenberg (1970) described allotype of IgA, using isoantibodies from a patient who displayed an anaphylactoid transfusion reaction. IgA2 has Am(1) and Am(2) genetic markers. The Am(1) allotype of IgA2 lacks the disulfide bond linking the heavy and light chains and instead consists of disulfide-bonded light chains joined noncovalently to a pair of disulfide-bonded heavy chains. Lefranc et al. (1983) first demonstrated the pseudogamma gene, which is located between the alpha-1 and gamma-2 (147110) genes (Migone et al., 1984). By Northern blot, RT-PCR, sequence, and Western blot analyses, Hatzivassiliou et al. (2001) demonstrated that the signal peptide and first 2 extracellular residues of IRTA1 (605876) are fused to the extracellular spacer, transmembrane domain, and cytoplasmic tail of the membrane IgA1 receptor (IGHA1) in the FR4 multiple myeloma (MM) cell line, but not in other MM or lymphoma cell lines. They concluded that the IRTA1-IGHA1 fusion may be a rare event in B-cell malignancy. Tomana et al. (1997) found that serum IgA1 protein isolated from patients with IgA nephropathy (IGAN1; 161950) were galactosylated to a lesser degree compared to controls. The galactose deficiency was in the O-linked side chains located in the hinge region of the IgA1 molecule. Incompletely galactosylated IgA1 was detected in complexes with IgG, supporting the hypothesis that the formation of abnormal IgA1-IgG complexes impairs the rate of elimination and hepatic catabolism of IgA1 in patients with IgA nephropathy. Using mass spectrometry to evaluate 290 renal biopsy specimens and 4 serum samples from patients with IgA nephropathy, Hiki et al. (2001) found that the numbers of carbohydrates composing O-glycans in the hinge region of IgA1 were significantly fewer in both deposited and serum IgA1 molecules in patients compared to controls. Suzuki et al. (2008) found excess sialylation of GalNAc on the Gal-deficient O-linked glycans of IgA1 in cell lines from IgA nephropathy patients. There was decreased expression and activity of C1GALT1 (610555), a galactosyltransferase, and its molecular chaperone C1GALT1C1 (300611) in IgA1 nephropathy cells compared to controls. In contrast, STGALNAC2 (610137), a sialyltransferase, showed increased expression and activity in IgAN cells. Suzuki et al. (2008) concluded that premature sialylation underlies the IgA1 Gal deficiency in IgAN. ... More on the omim web site

Subscribe to this protein entry history

Oct. 20, 2018: Protein entry updated
Automatic update: OMIM entry 146900 was added.

Oct. 19, 2018: Additional information
Initial protein addition to the database. This entry was referenced in Bryk and co-workers. (2017).