Hemoglobin subunit alpha N-terminal valine (HBA N-terminal valine)

Hemoglobin subunit alpha (HBA) is a fundamental protein component of the adult hemoglobin tetramer, which is responsible for the vital transport of oxygen from the lungs to peripheral tissues (UniProt P69905). In patients with sickle cell disease (SCD), a genetic mutation in the beta-globin chain (HbS) causes hemoglobin to polymerize when it is in the deoxygenated state, leading to the characteristic sickling of red blood cells and subsequent hemolysis (Vichinsky et al., NEJM, 2019). The N-terminal valine of the alpha chain has been identified as a critical therapeutic target for allosteric modulators such as voxelotor. By binding covalently and reversibly to this specific site, these drugs increase the oxygen affinity of the hemoglobin molecule, effectively stabilizing it in the oxygenated, or R-state, conformation (Oksenberg et al., British Journal of Haematology, 2016). Because only the deoxygenated (T-state) form of sickle hemoglobin is prone to polymerization, this stabilization prevents the formation of the rigid polymers that drive the clinical manifestations of SCD. Consequently, targeting the alpha chain N-terminus provides a mechanism to reduce red blood cell destruction and improve oxygen carrying capacity in patients with sickle cell disease (FDA, Oxbryta Prescribing Information, 2019).

Other names

Alpha-globin N-terminal valineHBA1 N-terminusHBA2 N-terminusHemoglobin alpha chain N-terminal valineAlpha-chain N-terminal valine

Allosteric modulation via covalent binding to the N-terminal valine of the alpha-globin chain, which increases hemoglobin's affinity for oxygen and stabilizes the oxygenated (R-state) conformation, thereby inhibiting the polymerization of deoxygenated sickle hemoglobin (HbS) (FDA, Oxbryta Prescribing Information, 2019; Oksenberg et al., British Journal of Haematology, 2016).