Hemoglobin subunit alpha

Hemoglobin subunit alpha, Hemoglobin, alpha 1, is a hemoglobin protein that in humans is encoded by the HBA1 gene.

Gene
The human alpha globin gene cluster located on chromosome 16 spans about 30 kb and includes seven loci: 5'- zeta - pseudozeta - mu - pseudoalpha-1 - alpha-2 - alpha-1 - theta - 3'. The alpha-2 (HBA2) and alpha-1 (HBA1; this gene) coding sequences are identical. These genes differ slightly over the 5' untranslated regions and the introns, but they differ significantly over the 3' untranslated regions.

Protein
Two alpha chains plus two beta chains constitute HbA, which in normal adult life accounts for about 97% of the total hemoglobin; alpha chains combine with delta chains to constitute HbA-2, which with fetal hemoglobin (HbF), composed of alpha and gamma chains, make up the remaining 3% of adult hemoglobin.

Clinical significance
Alpha thalassemias result from deletions of each of the alpha genes as well as deletions of both HBA2 and HBA1; some nondeletion alpha thalassemias have also been reported.

Interactions
Hemoglobin subunit alpha has been shown to interact with hemoglobin subunit beta (HBB).