ATP-independent proteolysis of globin cyanogen bromide peptides in rabbit reticulocyte cell-free extracts

The catabolism of two rabbit globin cyanogen bromide peptides in cell-free extracts of ATP-depleted rabbit reticulocytes has been studied. Proteolysis of the peptides (3533 and 5957 molecular weight) proceeded rapidly in the absence of ATP, had a pH optimum of approximately 7.8, and was inhibited by omicron-phenanthroline, N-ethylmaleimide, cystamine zinc and cobalt ions, and puromycin peptide high-molecular-weight aggregates. Proteolysis of puromycin peptides was inhibited by the rabbit globin cyanogen bromide peptides. The ability of cell-free extracts of degrade the globin cyanogen bromide peptides decreased with the reticulocyte maturity. Blocking the globin cyanogen bromide peptide amino groups by succinic and maleic anhydride treatment decreased susceptibility to degradation. It is suggested that the globin cyanogen bromide peptides might provide model substrates, replacing puromycin peptides, for the investigation of ATP-independent proteolytic events.