Protein Synthesis Directed by Polyadenylated and Non‐polyadenylated RNA: Isolated from Membrane‐Bound and Free Polysomes of Tetrahymena pyriformis

Free and membrane‐bound polysomes were prepared from the protozoa Tetrahymena pyriformis using a procedure which gives good recovery and practically no cross‐contamination. Polysomes are intact as analysed by sedimentation analysis. Poly(A)‐rich RNA and poly(A)‐free RNA, isolated from both populations of polysomes, show similar electrophoretic patterns. These RNAs were translated in the rabbit reticulocyte lysate cell‐free system and the translation products were analysed by one‐dimensional and two‐dimensional gel electrophoresis. The most striking differences were found in the two‐dimensional electrophoretic analysis namely: (a) a group of polypeptides (10) is synthesized mainly on membrane‐bound polysomes, (b) a second abundant group is synthesized mainly in free polysomes (c) and a third class of polypeptides is synthesized on both kinds of polysomes. Poly(A)‐free RNAs, isolated from free polysomes, are also able to promote synthesis of some polypeptides. The results are discussed taking into account the fact that T. pyriformis is a non‐secretory cell.