Effects of ATP and cell development on the metabolism of high molecular weight aggregates of abnormal proteins in rabbit reticulocytes and cell-free extracts

Abnormal proteins synthesized in rabbit reticulocytes in response to (i) the lysine analogue aminoethylcysteine and (ii) puromycin, form high molecular weight aggregates prior to degradation. Inhibitors of ATP synthesis partially inhibit catabolism of the aminoethylcysteine-induced abnormal protein; degradation of puromycin peptides synthesized after incubation with 25 μg/ml puromycin was not inhibited. Catabolism of the analogue-induced high molecular weight aggregate of abnormal protein in cell-free extracts was markedly stimulated by ATP, whereas proteolysis of the aggregated puromycin-peptides was ATP-independent. The ability of the reticulocytes to degrade the puromycin-peptide aggregates was found to decrease with cellular maturity. It is suggested that the energy-dependency for proteolysis is in some way related to the chain length of the abnormal protein synthesized.