POLYRIBOSOME BREAKDOWN AND HEMOGLOBIN SYNTHESIS

Abstract

The breakdown of polyribosomes in the reticulocyte cell-free system occurred only during protein synthesis and was accompanied by the release of completed chains. The largest sizes of polyribosomes disappeared first, followed in order by the other sizes. Inhibition of hemoglobin synthesis by poly A resulted in an increased rate of orderly breakdown. Indirect evidence for reattachment of 80S ribosomes to polyribosomes was presented. These results support a mechanism of protein synthesis, involving attachement of 80S ribosomes to the polyribosome which initiates the formation of the peptide chain, followed by chain growth and finally detachment of the ribosome and release of the completed polypeptide chain.