Afamin (AFM)
The protein contains 599 amino acids for an estimated molecular weight of 69069 Da.
Functions as carrier for hydrophobic molecules in body fluids (Probable). Essential for the solubility and activity of lipidated Wnt family members, including WNT1, WNT2B, WNT3, WNT3A, WNT5A, WNT7A, WNT7B, WNT8, WNT9A, WNT9B, WNT10A and WNT10B (PubMed:26902720). Binds vitamin E (PubMed:15952736, PubMed:12463752). May transport vitamin E in body fluids under conditions where the lipoprotein system is not sufficient (PubMed:15952736). May be involved in the transport of vitamin E across the blood-brain barrier (PubMed:19046407). (updated: Feb. 28, 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.
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| Variant | Description |
|---|---|
| dbSNP:rs41265665 | |
| dbSNP:rs2276444 |
Biological Process
Protein stabilization
Protein transport within extracellular region
Vitamin transport
Cellular Component
Blood microparticle
Cytoplasm
Extracellular exosome
Extracellular region
Extracellular space
The reference OMIM entry for this protein is 104145
Afamin; afm
Alpha-albumin; alba; alb2
Belanger et al. (1994) identified a fourth member of the albumin gene family, the others being albumin (ALB; 103600), alpha-fetoprotein (AFP; 104150), and vitamin D-binding protein (DBP; 139200). The 'new' gene, called alpha-albumin, was located 10 kb downstream from the AFP locus. The gene is selectively expressed in the liver at late stages of development. The mRNA sequence encodes a predicted secreted protein with the typical triple domain disulfide cross-linked structure. Comparisons of coding and promoter sequences suggested that ALBA could be a phylogenetic intermediate between the ALB and AFP genes. The developmental switch between ALBA gene activation and AFP gene repression suggested new regulatory interplays at the albumin locus and adult stage-specific ligand binding functions carried out by the ALBA gene product. The ALB and DBP genes diverged before the emergence of amphibians 500 Myr ago, while the AFP gene evolved slowly after the amphibian/reptile separation 350 Myr ago. The fact that the 3 genes have remained closely linked in single copy per haploid genome suggests a selective advantage to their proximity, plausibly provided by shared cis-regulatory elements. The sequence of the 3 most closely related genes is 5-prime--ALB--AFP--ALBA--3-prime. Lichenstein et al. (1994) described the initial characterization of afamin and its cDNA and provided evidence that AFM is a novel member of the albumin family. This serum protein, with a molecular mass of 87,000 Da, was purified to homogeneity and subjected to amino acid sequence analyses. These sequences were used to design oligonucleotide primers and to isolate a full-length cDNA. The amino acid sequence encoded by the cDNA was found to share strong similarity to albumin family members, including the characteristic pattern of cys residues observed in that family. The gene maps to chromosome 4 as do other members of the albumin gene family. The mapping was performed by PCR applied to a panel of somatic cell hybrids. Noteworthy distinctions among ALB family members include the following: concentrations in adult serum are 50 ng/ml for AFP, 350 microg/ml for DBP, 40 mg/ml for ALB, and 30 microg/ml for AFM. ALB is not N-glycosylated, AFP and DBP each have 1 potential N-glycosylation site, and AFM has 4 potential sites. ALB expresses 1 free thiol group that has been implicated in complex formation with cysteine, glutathione, and mercurial and gold compounds. In contrast, the other 3 have an even number of cys residues, are thought not to have a free thiol, and may not bind glutathione and mercurials as does ALB. Nishio and Dugaiczyk (1996) showed that the approximately 23-kb alpha-albumin gene contains 15 exons, the last of which is untranslated. The predicted protein has a 21-amino acid leader sequence followed by a 578-residue mature polypeptide. The exon structure is similar to that of the related genes for albumin, alpha-fetoprotein, and vitamin D-binding protein. Four genes, vitamin D binding protein/Gc-globulin (DBP; 139200), alpha-fetoprotein (AFP; 104150), alpha-albumin/afamin (AFM; 104145), and the ALB gene, represent a multigene cluster. The 4 genes have structural and functional similarities and map to the same chromosomal region in humans, mice, and rats. By refining the physical and meiotic maps of the 4q11-q13 region and creating a local PAC contig, Song et al. (1999) determined the order and transcriptional orientation of these 4 genes to be centromere--3-prime-DBP-5-p ... More on the omim web site
April 12, 2018: Protein entry updated
Automatic update: Entry updated from uniprot information.
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
June 20, 2017: Protein entry updated
Automatic update: comparative model was added.
March 25, 2017: Additional information
No protein expression data in P. Mayeux work for AFM
March 16, 2016: Protein entry updated
Automatic update: OMIM entry 104145 was added.