Analyses of globin release from reticulocyte ribosomes

Abstract

Investigations of the biosynthetic processes which constitute the respective stages of protein synthesis indicate the presence of a specific mechanism for the release of completed protein from the biosynthetic template (Morris, 1964). It was demonstrated early in the studies of protein biosynthesis that cell-free systems prepared from rabbit reticulocytes synthesize hemoglobin molecules which are no longer attached to the ribosomal template and are chromatographically indistinguishable from carrier hemoglobin (Schweet et al , 1958) . The details of the process by which completed protein chains are liberated to a nonparticulate state have been a subject of previous publications from this laboratory. It is the purpose of this communication to present the results of further studies which indicate the release of globin molecules from reticulocyte ribosomes involves cleavage of the globyl-sRNA bond at the ribosomal level and that the first soluble product of the release reaction is the protein molecule, free from soluble RNA. A mechanism for the termination and release of completed protein chains from the ribosomal template is proposed.