Initiation of globin synthesis in β thalassemia
The mechanism of initiation of human globin chains was examined to determine if the initiation of protein synthesis is abnormal in β thalassemia. Messenger RNA (mRNA) was isolated from the reticulocytes of normal adults, newborn infants and patients with β thalassemia to study synthesis of alpha, beta and gamma chains. These isolated mRNA preparations were assayed in a cell free system derived from rabbit reticulocytes. The initial dipeptides formed during the synthesis of the alpha and beta chains were determined. In normal subjects and patients with β thalassemia the dipeptide for both the alpha and beta chains was found to be methionine valine. The initial dipeptide for the gamma chain, determined in newborn infants and in patients with β thalassemia, was methionine glycine in both. All mRNA's studied shared a common requirement for methionyl tRNA(F) (the specific initiator tRNA) and for the protein initiation factors. By these criteria, the mechanism of globin chain initiation in β thalassemia is normal.