Rapid proteolysis of unstable globins in human bone marrow

To determine whether human red cells contain a proteolytic system capable of rapidly degrading unstable proteins, the fate of pulse-labelled puromycyl polypeptides was investigated. In erythroid bone marrow cells these unstable polypeptides were degraded to TCA-soluble fragments with a mean half-life of 4 . 5 min. However, in peripheral blood reticulocytes no proteolysis was observed, indicating that this activity declines as the red cell matures.