Terminal stages in the biosynthesis of haemoglobin. The release of protein from reticulocyte ribosomes

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Abstract
The release of 14c-labelled protein from previously 14C-labeled reticuloeyte ribosomes, and the incorporation of 14C-labeled amino acids into unlabeled ribosomes prepared in a parallel manner, were determined in order to assess the influence of the incorporation of amino acids on the release of proteins in a cell-free system, The protein-release process consists of two distinct steps, each possessing different requirements. The first step consists of those processes involved in the completion of protein chains before release from the ribosome. The second step, the release of protein from the ribosome, proceeds independently of the completion process. An absolute requirement for the presence of GTP has been demonstrated in the protein-release reaction. Characterization of the soluble product of the protein-release reaction has shown the presence of the [alpha]- and [beta]-globin chains of hemoglobin which are not yet in the form of the finished hemoglobin molecule.