55 kDa erythrocyte membrane protein (MPP1)
The protein contains 466 amino acids for an estimated molecular weight of 52296 Da.
Essential regulator of neutrophil polarity. Regulates neutrophil polarization by regulating AKT1 phosphorylation through a mechanism that is independent of PIK3CG activity (By similarity). (updated: Feb. 4, 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.
- Lange and co-workers. (2014) Annotating N termini for the human proteome project: N termini and Nα-acetylation status differentiate stable cleaved protein species from degradation remnants in the human erythrocyte proteome. J Proteome Res. 13(4), 2028-2044.
- 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.
- Wilson and co-workers. (2016) Comparison of the Proteome of Adult and Cord Erythroid Cells, and Changes in the Proteome Following Reticulocyte Maturation. Mol Cell Proteomics. 15(6), 1938-1946.
- 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.
- Chu and co-workers. (2018) Quantitative mass spectrometry of human reticulocytes reveal proteome-wide modifications during maturation. Br J Haematol. 180(1), 118-133.
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 Gene Ontology, is annotated as membranous in UniProt.
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| Variant | Description |
|---|---|
| dbSNP:rs14092 |
Biological Process
Nucleotide phosphorylation
Regulation of neutrophil chemotaxis
Signal transduction
The reference OMIM entry for this protein is 305360
Membrane protein, palmitoylated 1; mpp1
Erythrocyte membrane protein p55; emp55
Palmitoylated erythrocyte membrane protein; pemp
DESCRIPTION
EMP55 is the prototype of a family of membrane-associated proteins termed MAGUKs (membrane-associated guanylate kinase homologs). MAGUKs interact with the cytoskeleton and regulate cell proliferation, signaling pathways, and intracellular junctions (Kim et al., 1996).CLONING
Ruff et al. (1991) deduced the complete amino acid sequence of a 55-kD erythrocyte membrane protein from cDNA clones isolated from a human reticulocyte library. This protein, p55, was copurified during the isolation of dematin, an actin-bundling protein of the erythrocyte membrane cytoskeleton. Its tight association with the plasma membrane was reminiscent of an integral membrane protein. Protein p55 is the most extensively palmitoylated protein of the erythrocyte membrane. Predicted primary structure of p55 contained a conserved sequence, called the SH3 (src homology 3) motif, found in several other proteins that associate with the cytoskeleton and are suspected to play important roles in signal transduction. Metzenberg and Gitschier (1992) found a gene located in a CpG island 30 kb 3-prime to the factor VIII gene (F8; 300841). The 2-kb transcript encoded a previously described palmitoylated membrane protein, p55, containing an src homology motif, SH3. Although originally described in reticulocytes (Ruff et al., 1991), Metzenberg and Gitschier (1992) found that the transcript was expressed in a wide variety of human tissues. The gene was also found in the mouse where it was expressed in all tissues examined. The EMP55 gene did not appear to be developmentally regulated in erythrocytes; p55 is constitutively and abundantly expressed in erythroid cells during their development from stem cells to fully differentiated reticulocytes. In contrast, other red cell membrane-associated proteins such as 4.1, ankyrin, and band 3 are expressed late in erythropoiesis. These results suggested that the p55 protein may have a housekeeping function. Other work indicated that it is a peripheral membrane protein. Bryant and Woods (1992) demonstrated that p55 is homologous to the yeast guanylate kinase and to the product of a Drosophila tumor suppressor gene. Elder et al. (1996) cloned and sequenced the mouse MPP1 gene. The mouse gene shares 89% sequence identity with the coding sequence of human MPP1. The coding region size and intron/exon structures of the mouse and human genes are identical. The human and mouse sequences and structures are highly homologous to the MPP1 gene of fish (Fugu), suggesting that the gene serves an essential function in development.GENE FUNCTION
By yeast 2-hybrid analysis of a mouse embryo cDNA library, Mburu et al. (2006) found that whirlin (WHRN; 607928) interacted with p55. p55 was expressed in mouse outer hair cells in long stereocilia that made up the stereocilia bundle and in surrounding shorter stereocilia structures. Since p55 and protein 4.1R (EPB41; 130500) form complexes critical for actin cytoskeletal assembly in erythrocytes, Mburu et al. (2006) proposed that p55 and whirlin may have a similar role in hair cell stereocilia.GENE STRUCTURE
Metzenberg and Gitschier (1992) estimated that the EMP55 gene spans 20 to 30 kb. Kim et al. (1996) reported the complete intron/exon map of the human erythroid p55 gene. The structure of the p55 gene was determined from cosmid clones isolated from a cosmid library specific for the human X chromosome. There is a single copy of the p55 gene, composed of 1 ... 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 15, 2016: Protein entry updated
Automatic update: OMIM entry 305360 was added.
Jan. 24, 2016: Protein entry updated
Automatic update: model status changed