Coatomer subunit alpha (COPA)
The protein contains 1224 amino acids for an estimated molecular weight of 138346 Da.
The coatomer is a cytosolic protein complex that binds to dilysine motifs and reversibly associates with Golgi non-clathrin-coated vesicles, which further mediate biosynthetic protein transport from the ER, via the Golgi up to the trans Golgi network. Coatomer complex is required for budding from Golgi membranes, and is essential for the retrograde Golgi-to-ER transport of dilysine-tagged proteins. In mammals, the coatomer can only be recruited by membranes associated to ADP-ribosylation factors (ARFs), which are small GTP-binding proteins; the complex also influences the Golgi structural integrity, as well as the processing, activity, and endocytic recycling of LDL receptors (By similarity).', 'Xenin stimulates exocrine pancreatic secretion. It inhibits pentagastrin-stimulated secretion of acid, to induce exocrine pancreatic secretion and to affect small and large intestinal motility. In the gut, xenin interacts with the neurotensin receptor. (updated: April 1, 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.
- 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.
- 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.
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| Variant | Description |
|---|---|
| RNA edited version | |
| dbSNP:rs34997807 | |
| AILJK | |
| AILJK | |
| AILJK | |
| AILJK |
Biological Process
COPI coating of Golgi vesicle
Endoplasmic reticulum to Golgi vesicle-mediated transport
Intra-Golgi vesicle-mediated transport
Intracellular protein transport
Membrane organization
Pancreatic juice secretion
Protein localization to axon
Protein localization to cell leading edge
Retrograde vesicle-mediated transport, Golgi to endoplasmic reticulum
The reference OMIM entry for this protein is 601924
Coatomer protein complex, subunit alpha; copa
Alpha coat protein coatomer protein complex, included; copi, included
DESCRIPTION
The COPA gene encodes a subunit of the coatomer protein complex (COPI), a carrier complex required for retrograde protein trafficking from the Golgi to the endoplasmic reticulum (ER) (summary by Watkin et al., 2015).CLONING
Chow and Quek (1996) reported the cDNA sequence encoding the COPA gene, which the authors called HEP-COP. The open reading frame predicts a 1,224-amino acid polypeptide that shares high sequence similarity with RET1P, the alpha subunit of the coatomer complex in yeast. Using antibodies against COPA in Western blot analysis of protein lysates from human hepatoma cell lines, Quek and Chow (1997) showed that COPA migrates as an approximately 160-kD protein. Immunoblotting of subcellular components of Hep3B cells revealed that COPA is located predominantly in the microsomal and cytosolic fractions; COPA was virtually absent in the nuclear compartment. Indirect immunofluorescence of Hep3B cells showed that COPA is located chiefly in the cytoplasm.GENE FUNCTION
COPI is a heptameric protein recruited to membranes by ARF1 (103180), a GTP-binding protein. Coat assembly helps in the transport of budding off membrane between the ER and Golgi apparatus. Using fluorescence microscopy, Presley et al. (2002) showed that guanine nucleotide exchange-activated ARF1 at the Golgi membrane recruits and binds cytoplasmic COPI to the membranes. Photobleaching experiments demonstrated that COPI remains at the membranes after ARF1-GTP has been hydrolyzed by ARFGAP1 (608377). COPI binds to membrane cargo, soluble-cargo receptors, or other Golgi proteins. Uncoating, or the release of COPI from Golgi membranes to the cytoplasm, then occurs, which can be inhibited by aluminum fluoride. Presley et al. (2002) concluded from their kinetic and biochemical analyses that COPI and ARF1 continuously bind and release from Golgi membranes, allowing the membrane at these sites to recruit cargo, alter their phospholipid composition, and become larger, phase-separated domains. Liu et al. (2003) found that a central region of Xenopus Nup153 (603948) associated with COPI. Nup153 recruited COPI to the nuclear membrane during mitosis, suggesting that vesiculation is an important step in nuclear envelope breakdown. Perturbing the function of the COPI complex impaired nuclear envelope disassembly. Park et al. (2015) showed that the COPI complex sorts anterograde cargoes into tubules that connect the Golgi cisternae in human cells. Moreover, the small GTPase CDC42 (116952) regulates bidirectional Golgi transport by targeting the dual functions of COPI in cargo sorting and carrier formation. CDC42 also directly imparts membrane curvature to promote COPI tubule formation. Park et al. (2015) concluded that their findings further revealed that COPI tubular transport complements cisternal maturation in explaining how anterograde Golgi transport is achieved, and that bidirectional COPI transport is modulated by environmental cues through CDC42.GENE STRUCTURE
Quek and Chow (1997) reported the genomic organization of the COPA gene. It contains 33 exons ranging in size from 67 to 611 bp. All exon-intron junctions conform with the GT-AG rule. The 32 introns range from about 80 bp to 4 kb, with the genomic DNA of COPA estimated to span approximately 37 kb. The untranscribed and noncoding portions of the 5-prime end of the gene lacked TATA and CAAT boxes but displayed a high GC content, consistent with its being a hous ... 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 16, 2016: Protein entry updated
Automatic update: OMIM entry 601924 was added.