Studies of the terminal stages of hemoglobin synthesis. II. Lack of effect of alpha and beta hemoglobin chains on the rate of globin synthesis in a human cell-free system.

The influence of heme containing alpha A and beta S globin chains on the rate of synthesis of globin subunits has been studied in a human cell-free system derived from sickle reticulocytes. The autologous lysate system produced measurable amounts of nascent protein as equal amounts of alpha and nonalpha chains, which were released as soluble globin. The addition of either alpha A or beta S hemoglobin chains in concentrations between 10(-5)M and 10(-8)M did not alter either the rate of total globin synthesis or the alpha/beta synthesis ratio. The results suggest that the presence of free hemoglobin chains within the cell does not in itself affect the rate of globin chain synthesis and that other mechanisms within the cell are more important in coordinating the synthesis of equal amounts of alpha and nonalpha globin chains. One cannot conclude that there is no effect on chain initiation, since in the mammalian systems very littl chain initiation occurs.