The release of protein from reticulocyte ribosomes

Abstract

The mechanism of polypeptide formation has been studied ir great detail in recent years through the use of cell-free systems. In general one can distinguish three stages of synthesis: 1) the activation of amino acids by ATP and amino acid specific enzymes, 2) the attachment of amino acids to soluble RNA through a high energy ester bond, and 3) the transfer of bound amino acids to the ribosome with conourrent formation of ribosomal bound polypeptide material. The present investigation is concerned with yet another stage in protein synthesis, the release of completed protein molecules from the ribosome. This release, as studied in a cell-free system from rabbit reticulocytes, has been shown to be independent of the earlier steps in protein synthesis. The release specifically requires guanosine triphosphate (GTP) and possesses the character of an enzyme catalyzed reaction. It is independent of the processes of peptide synthesis.