Hemoglobin subunit mu (HBM)
The protein contains 141 amino acids for an estimated molecular weight of 15618 Da.
No function (updated: Jan. 7, 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.
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The reference OMIM entry for this protein is 609639
Hemoglobin mu
Hbm
CLONING
Using postgenomic approaches to examine the transcriptional profiles of human reticulocytes, Goh et al. (2005) characterized a previously undefined transcript representing an unrecognized globin gene that showed homology to the pseudo-HbA2 region within the alpha-globin locus (see 141800) on chromosome 16p13.3. Cloning and sequencing of that transcript, named hemoglobin (Hb) mu (HBM), revealed an insert with a 423-nucleotide open reading frame. The predicted protein demonstrated a high level of homology with the avian alpha-D globin. In addition, the heme- and globin-binding amino acids of mu-globin and avian alpha-D globin were largely conserved. Using quantitative real-time PCR, mu-globin was detected at a level of approximately 0.1% of that measured for alpha-globin in erythroid tissues. Erythroid-specific expression was detected by Northern blot analysis, and maximal expression during the erythroblast terminal differentiation was also detected. Despite this highly regulated pattern of mu-globin gene transcription, mu-globin protein was not detected by mass spectrometry. These results suggested that the human genome encodes a previously unrecognized globin member of the avian alpha-D family that is transcribed in a highly regulated pattern in erythroid cells.GENE FUNCTION
Goh et al. (2005) commented that it is curious that mu-globin is not the only gene in the human alpha-globin cluster that lacks a detectable hemoglobin product. The downstream region of the alpha locus contains an unusual gene named theta-globin (HbQ1; 142240) that generates no detected globin protein in humans. Theta-globin gene transcription is regulated, and the transcripts contain no obvious defects to explain the lack of detectable protein in erythroid tissues. Both the HBM and HbQ1 genes are well conserved at the genomic level, and both have a highly regulated pattern of transcription in erythroid cells. It was uncertain whether the HBM gene is evolving toward becoming a pseudogene; Goh et al. (2005) raised the possibility that instead, this ancient globin has a function for which high-level protein expression is not required.GENE STRUCTURE
Goh et al. (2005) determined that the HBM gene has a 3-exon structure similar to that of other human hemoglobin alpha genes.MAPPING
The HBM gene maps to the alpha-globin region on chromosome 16p13.3, overlapping the pseudo-Hb2 gene (Goh et al., 2005). ... 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
June 20, 2017: Protein entry updated
Automatic update: comparative model was added.
March 16, 2016: Protein entry updated
Automatic update: OMIM entry 609639 was added.