The characterization of separated alpha and beta-chain polyribosomes in rabbit reticulocytes.

Abstract Incubation of rabbit reticulocytes with l-O-methylthreonine, an analogue of isoleucine, results in the formation of polyribosome aggregates containing 10 to 14 ribosomes, and an increase in the number of polyribosomes with 2 to 3 ribosomes. Of the very large polyribosomes 86% contain nascent β polypeptide chains of hemoglobin. On the other hand, 68% of the small aggregates carry nascent α chains. In control reticulocytes the α and β chain polyribosomes are approximately equal in number in both these fractions. Furthermore, in cells incubated with l-O-methylthreonine, the total quantity of β chain ribosomes markedly exceeds that of α chain ribosomes. These data provide direct support for the theory of ribosomal movement in the translation of messenger RNA.