Hemopexin (HPX)
The protein contains 462 amino acids for an estimated molecular weight of 51676 Da.
Binds heme and transports it to the liver for breakdown and iron recovery, after which the free hemopexin returns to the circulation. (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.
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| Variant | Description |
|---|---|
| dbSNP:rs10839564 | |
| dbSNP:rs12117 |
No binding partner found
Biological Process
Cellular iron ion homeostasis
Heme metabolic process
Heme transport
Hemoglobin metabolic process
Positive regulation of humoral immune response mediated by circulating immunoglobulin
Positive regulation of immunoglobulin production
Positive regulation of interferon-gamma-mediated signaling pathway
Positive regulation of tyrosine phosphorylation of STAT protein
Receptor-mediated endocytosis
Viral process
The reference OMIM entry for this protein is 142290
Hemopexin; hpx
DESCRIPTION
Hemopexin is a plasma beta-glycoprotein that specifically binds one heme with high affinity and transports it to hepatocytes for salvage of iron (summary by Takahashi et al., 1985).CLONING
Takahashi et al. (1985) determined that human hemopexin consists of a single polypeptide chain of 439 amino acids and has a molecular mass of approximately 63 kD. Altruda et al. (1985) also determined the protein sequence of human hemopexin. Both groups noted that hemopexin is low in patients with hemolysis. Naylor et al. (1987) found that hemopexin mRNA was present at a low level in fetal liver, increased dramatically in adult liver, and was not detectable in other tissues.GENE STRUCTURE
Altruda et al. (1988) demonstrated that the HPX gene spans approximately 12 kb and is interrupted by 9 exons. A direct correspondence between exons and the 10 repeating units in the protein was shown. The introns were not randomly placed; they fell in the middle of the region of amino acid sequence homology in strikingly similar locations in 6 of the 10 units and in a symmetric position in each half of the coding sequence. From these findings, Altruda et al. (1988) concluded that the gene evolved through intron-mediated duplications of a primordial sequence to a 5-exon cluster. A more recent gene duplication led to the present-day gene organization.MAPPING
Cai and Law (1986) prepared a cDNA clone for hemopexin and, by Southern blot analysis of human/hamster hybrids containing different combinations of human chromosomes, assigned the hemopexin gene to human chromosome 11. Naylor et al. (1987) used a hemopexin cDNA clone to map the HPX gene to 11pter-p11 by somatic cell hybrid analysis. By means of in situ hybridization, Law et al. (1988) assigned the hemopexin gene to 11p15.5-p15.4, the same location as that of the beta-globin gene complex.MOLECULAR GENETICS
Hemopexin has been found in the serum of all mammals studied and it is polymorphic in rabbits. Stewart and Lovrien (1971) found no electrophoretic polymorphism in humans. Polymorphism of hemopexin is known in the pig (Lush, 1966). By isoelectric focusing, Kamboh and Ferrell (1987) demonstrated polymorphism of HPX in US blacks but not in US whites. Data on gene frequencies of allelic variants were tabulated by Roychoudhury and Nei (1988). ... More on the omim web site
June 30, 2020: Protein entry updated
Automatic update: OMIM entry 142290 was added.
Oct. 19, 2018: Additional information
Initial protein addition to the database. This entry was referenced in Bryk and co-workers. (2017).