GPI-anchor transamidase (PIGK)
The protein contains 395 amino acids for an estimated molecular weight of 45252 Da.
Mediates GPI anchoring in the endoplasmic reticulum, by replacing a protein's C-terminal GPI attachment signal peptide with a pre-assembled GPI. During this transamidation reaction, the GPI transamidase forms a carbonyl intermediate with the substrate protein. (updated: Sept. 12, 2018)
Protein identification was indicated in the following studies:
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 predicted to be membranous by TOPCONS.
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The reference OMIM entry for this protein is 605087
Phosphatidylinositol glycan, class k; pigk
Gpi8, yeast, homolog of; gpi8
DESCRIPTION
Glycosylphosphatidylinositol (GPI) is a membrane anchor for cell surface proteins. PIGK is a subunit of the GPI transamidase complex that catalyzes the attachment of preformed GPI to proteins containing a C-terminal GPI attachment site (Yu et al., 1997).CLONING
By searching an EST database for sequences similar to yeast Gpi8, Benghezal et al. (1996) identified a cDNA encoding PIGK, which they called GPI8. Sequence analysis predicted that the 396-amino acid PIGK protein shares 43% amino acid identity with yeast Gpi8. Yu et al. (1997) identified a mutant cell line that fails to incorporate GPI anchors into nascent N-terminally processed proproteins due to a defect in transamidation. By PCR analysis using the PIGK sequence reported by Benghezal et al. (1996), Yu et al. (1997) identified additional upstream sequences, including an ATG initiation codon. Expression of this PIGK cDNA in the mutant cell line restored GPI anchor assembly. Northern blot analysis detected major 1.6- and 1.9-kb PIGK transcripts in HeLa and K562 cell lines.GENE STRUCTURE
By Southern blot analysis of genomic DNA, Yu et al. (1997) found that the PIGK gene spans 20 to 25 kb.MAPPING
By somatic cell hybrid analysis, Yu et al. (1997) mapped the PIGK gene to chromosome 1.GENE FUNCTION
By mutation analysis, Ohishi et al. (2003) determined that cys92 of GPI8 and cys182 of PIGT (610272) form an intermolecular disulfide bond. The disulfide bond was not necessary for the formation of the GPI transamidase complex or for its transamidase activity. However, mutation of GPI8 cys206-to-ser resulted in an inactive complex becasue cys206 is within the active site of the GPI transamidase. ... More on the omim web site
June 30, 2020: Protein entry updated
Automatic update: OMIM entry 605087 was added.
Oct. 19, 2018: Additional information
Initial protein addition to the database. This entry was referenced in Bryk and co-workers. (2017).