Polyribosomes Active in Reticulocyte Protein Synthesis

Excerpt

Previous studies with bacteria (Tissières et al., 1960; Spyrides and Lipmann, 1962; Barondes and Nirenberg, 1963; Gilbert, 1963b) and reticulocytes (Marks et al., 1962; Warner et al., 1963; Gierer, 1963), as well as other mammalian cells (Wettstein et al., 1963; Penman et al., 1963) indicate that protein synthesis proceeds primarily on polyribosomes which are clusters of 2 or more ribosomes. It has been proposed that the polyribosomes are composed of a number of 78S ribosomes attached to a strand of messenger-RNA along which they move as the peptide chain grows.

One of the initial problems addressed by the present investigations was to determine the proportion of ribosomes arranged as polyribosomes in the cell. For these studies reticulocytes were prepared from the blood of rabbits with a phenylhydrazine-induced reticulocytosis (Borsook et al., 1952). The red cell population of these rabbits had 55 to 80% reticulocytes. The proportion of ribosomes arranged in...