Hemoglobin: Structure, synthesis and oxygen transport

Abstract

Human hemoglobin (Hb) is the erythrocyte hemeprotein resulting from the combination of one pair of α-like (α or ζ) chains and another pair of β-like (β, δ, γ or ε) chains. Each of these chains is associated with a heme prosthetic group, a tetrapyrrole ring (protoporphyrin IX) containing a central ferrous atom (Fe2+), which can reversibly bind to a molecule of O2, being, therefore, responsible for its transport from the lungs to the tissues. This introductory chapter summarizes these important aspects, including findings of protein structure, synthesis and function, as well as its gene organization and regulation. We also describe the developmental switches in globin chain production (from the embryonic period until hematological adult life), heme synthesis and globin gene expression/regulation, besides functional aspects of the hemoglobin molecule. The chapter also includes models that predict the mechanisms of Hb-O2 ligation, mediated by the presence of allosteric effectors, such as H+/CO2, Cl- and organic phosphates, such as 2,3-biphosphoglycerate (2,3-BPG, from erythrocyte metabolism).