Hemoglobin subunit beta

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Available structures
PDBOrtholog search: PDBe RCSB
AliasesHBB, CD113t-C, beta-globin, hemoglobin subunit beta, ECYT6
External IDsOMIM: 141900 MGI: 5474850 HomoloGene: 68066 GeneCards: HBB
RefSeq (mRNA)



RefSeq (protein)



Location (UCSC)Chr 11: 5.23 – 5.23 MbChr 7: 103.46 – 103.46 Mb
PubMed search[3][4]
View/Edit HumanView/Edit Mouse
In human, the HBB gene is located on chromosome 11 at position p15.5.

Hemoglobin subunit beta (beta globin, β-globin, haemoglobin beta, hemoglobin beta) is a globin protein, coded for by the HBB gene, which along with alpha globin (HBA), makes up the most common form of haemoglobin in adult humans, hemoglobin A (HbA).[5] It is 147 amino acids long and has a molecular weight of 15,867 Da. Normal adult human HbA is a heterotetramer consisting of two alpha chains and two beta chains.

HBB is encoded by the HBB gene on human chromosome 11. Mutations in the gene produce several variants of the proteins which are implicated with genetic disorders such as sickle-cell disease and beta thalassemia, as well as beneficial traits such as genetic resistance to malaria.[6][7] At least 50 disease-causing mutations in this gene have been discovered.[8]

Gene locus[edit]

HBB protein is produced by the gene HBB which is located in the multigene locus of β-globin locus on chromosome 11, specifically on the short arm position 15.4. Expression of beta globin and the neighbouring globins in the β-globin locus is controlled by single locus control region (LCR), the most important regulatory element in the locus located upstream of the globin genes.[9] The normal allelic variant is 1600 base pairs (bp) long and contains three exons. The order of the genes in the beta-globin cluster is 5' - epsilongamma-Ggamma-Adelta – beta - 3'.[5]


HBB interacts with Haemoglobin, alpha 1 (HBA1) to form haemoglobin A, the major haemoglobin in adult humans.[10][11] The interaction is two-fold. First, one HBB and one HBA1 combine, non-covalently, to form a dimer. Secondly, two dimers combine to form the four-chain tetramer, and this becomes the functional haemoglobin.[12]

Associated genetic disorders[edit]

Beta thalassemia[edit]

Beta thalassemia is an inherited genetic mutation in one (Beta thalassemia minor) or both (Beta thalassemia major) of the Beta globin alleles on chromosome 11. The mutant alleles are subdivided into two groups: β0, in which no functional β-globin is made, and β+, in which a small amount of normal β-globin protein is produced. Beta thalassemia minor occurs when an individual inherits one normal Beta allele and one abnormal Beta allele (either β0, or β+). Beta thalassemia minor results in a mild microcytic anemia that is often asymptomatic or may cause fatigue and or pale skin. Beta thalassemia major occurs when a person inherits two abnormal alleles. This can be either two β+ alleles, two β0 alleles, or one of each. Beta thalassemia major is a severe medical condition. A severe anemia is seen starting at 6 months of age. Without medical treatment death often occurs before age 12. [13] Beta thalassemia major can be treated by lifelong blood transfusions or bone marrow transplantation.[14][15]

According to a recent study, the stop gain mutation Gln40stop in HBB gene is a common cause of autosomal recessive Beta- thalassemia in Sardinian people (almost exclusive in Sardinia). Carriers of this mutation show an enhanced red blood cell count. As a curiosity, the same mutation was also associated to a decrease in serum LDL levels in carriers, so the authors suggest that is due to the need of cholesterol to regenerate cell membranes.[16]

Sickle cell disease[edit]

More than a thousand naturally occurring HBB variants have been discovered. The most common is HbS, which causes sickle cell disease. HbS is produced by a point mutation in HBB in which the codon GAG is replaced by GTG. This results in the replacement of hydrophilic amino acid glutamic acid with the hydrophobic amino acid valine at the seventh position (β6Glu→Val). This substitution creates a hydrophobic spot on the outside of the protein that sticks to the hydrophobic region of an adjacent hemoglobin molecule's beta chain. This further causes clumping of HbS molecules into rigid fibers, causing "sickling" of the entire red blood cells in the homozygous (HbS/HbS) condition.[17] The homozygous allele has become one of the deadliest genetic factors,[18] whereas people heterozygous for the mutant allele (HbS/HbA) are resistant to malaria and develop minimal effects of the anaemia.[19]

Haemoglobin C[edit]

Sickle cell disease is closely related to another mutant haemoglobin called haemoglobin C (HbC), because they can be inherited together.[20] HbC mutation is at the same position in HbS, but glutamic acid is replaced by lysine (β6Glu→Lys). The mutation is particularly prevalent in West African populations. HbC provides near full protection against Plasmodium falciparum in homozygous (CC) individuals and intermediate protection in heterozygous (AC) individuals.[21] This indicates that HbC has stronger influence than HbS, and is predicted to replace HbS in malaria-endemic regions.[22]

Haemoglobin E[edit]

Another point mutation in HBB, in which glutamic acid is replaced with lysine at position 26 (β26Glu→Lys), leads to the formation of haemoglobin E (HbE).[23] HbE has a very unstable α- and β-globin association. Even though the unstable protein itself has mild effect, inherited with HbS and thalassemia traits, it turns into a life-threatening form of β-thalassemia. The mutation is of relatively recent origin suggesting that it resulted from selective pressure against severe falciparum malaria, as heterozygous allele prevents the development of malaria.[24]

Human evolution[edit]

Malaria due to Plasmodium falciparum is a major selective factor in human evolution.[7][25] It has influenced mutations in HBB in various degrees resulting in the existence of numerous HBB variants. Some of these mutations are not directly lethal and instead confer resistance to malaria, particularly in Africa where malaria is epidemic.[26] People of African descent have evolved to have higher rates of the mutant HBB because the heterozygous individuals have a misshaped red blood cell that prevent attacks from malarial parasites. Thus, HBB mutants are the sources of positive selection in these regions and are important for their long-term survival.[6][27] Such selection markers are important for tracing human ancestry and diversification from Africa.[28]

See also[edit]


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  3. ^ "Human PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  4. ^ "Mouse PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  5. ^ a b "Entrez Gene: HBB hemoglobin, beta".
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  8. ^ Šimčíková D, Heneberg P (December 2019). "Refinement of evolutionary medicine predictions based on clinical evidence for the manifestations of Mendelian diseases". Scientific Reports. 9 (1): 18577. Bibcode:2019NatSR...918577S. doi:10.1038/s41598-019-54976-4. PMC 6901466. PMID 31819097.
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  10. ^ Stelzl U, Worm U, Lalowski M, Haenig C, Brembeck FH, Goehler H, Stroedicke M, Zenkner M, Schoenherr A, Koeppen S, Timm J, Mintzlaff S, Abraham C, Bock N, Kietzmann S, Goedde A, Toksöz E, Droege A, Krobitsch S, Korn B, Birchmeier W, Lehrach H, Wanker EE (2005). "A human protein-protein interaction network: a resource for annotating the proteome". Cell. 122 (6): 957–968. doi:10.1016/j.cell.2005.08.029. hdl:11858/00-001M-0000-0010-8592-0. PMID 16169070. S2CID 8235923.
  11. ^ Shaanan B (1983). "Structure of human oxyhaemoglobin at 2.1 A resolution". J. Mol. Biol. 171 (1). ENGLAND: 31–59. doi:10.1016/S0022-2836(83)80313-1. ISSN 0022-2836. PMID 6644819.
  12. ^ "Hemoglobin Synthesis". harvard.edu. Harvard University. 2002. Retrieved 18 November 2014.
  13. ^ H. Franklin Bunn, Vijay G. Sankaran (2017). "8". Pathology of blood disorders. pp. 927–933.
  14. ^ Muncie HL, Campbell J (2009). "Alpha and beta thalassemia". American Family Physician. 80 (4): 339–44. PMID 19678601.
  15. ^ "Beta thalassemia". Genetics Home Reference. U.S. National Library of Medicine. 11 November 2014. Retrieved 18 November 2014.
  16. ^ Sidore, C., et al. (2015). "Genome sequencing elucidates Sardinian genetic architecture and augments association analyses for lipid and blood inflammatory markers". Nature Genetics. 47 (11): 1272–1281. doi:10.1038/ng.3368. PMC 4627508. PMID 26366554.
  17. ^ Thom CS, Dickson CF, Gell DA, Weiss MJ (2013). "Hemoglobin variants: biochemical properties and clinical correlates". Cold Spring Harb Perspect Med. 3 (3): a011858. doi:10.1101/cshperspect.a011858. PMC 3579210. PMID 23388674.
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  19. ^ Luzzatto L (2012). "Sickle cell anaemia and malaria". Mediterr J Hematol Infect Dis. 4 (1): e2012065. doi:10.4084/MJHID.2012.065. PMC 3499995. PMID 23170194.
  20. ^ Piel FB, Howes RE, Patil AP, Nyangiri OA, Gething PW, Bhatt S, Williams TN, Weatherall DJ, Hay SI (2013). "The distribution of haemoglobin C and its prevalence in newborns in Africa". Scientific Reports. 3 (1671): 1671. Bibcode:2013NatSR...3E1671P. doi:10.1038/srep01671. PMC 3628164. PMID 23591685.
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Further reading[edit]

External links[edit]

  • Overview of all the structural information available in the PDB for UniProt: P68871 (Human Hemoglobin subunit beta) at the PDBe-KB.
  • Overview of all the structural information available in the PDB for UniProt: P02088 (Mouse Hemoglobin subunit beta-1) at the PDBe-KB.