alpha2beta2

Alpha2beta2 is the conventional designation for the adult hemoglobin tetramer, referred to as HbA. It consists of two alpha globin chains and two beta globin chains (α2β2) arranged in a quaternary structure that forms the core of oxygen transport in humans. HbA is the predominant form of hemoglobin in healthy adults, accounting for the vast majority of circulating hemoglobin.

Each globin chain binds a heme prosthetic group, containing an iron ion capable of reversibly binding oxygen. The HbA tetramer can carry up to four oxygen molecules, one per heme group. Oxygen binding exhibits cooperativity, producing a sigmoidal oxygen dissociation curve that enables efficient uptake in the lungs and release in tissues. The affinity of HbA for oxygen is modulated by factors such as pH, carbon dioxide concentration, temperature, and 2,3-bisphosphoglycerate (2,3-BPG), which promotes oxygen release in peripheral tissues.

Developmental variants include HbA2, which is α2δ2, and fetal hemoglobin HbF, which is α2γ2. Hemoglobin disorders often involve the globin genes encoding the alpha or beta chains, leading to conditions such as alpha or beta-thalassemias and sickle cell disease, the latter caused by a Glu-to-Val substitution in the beta chain of HbA.

In biochemistry and physiology, alpha2beta2 denotes the stoichiometry and organization of the HbA tetramer, distinguishing it from other hemoglobin isoforms with different subunit compositions.