Degradation of Abnormal Proteins in Escherichia coli: Relative Susceptibility of Canavanyl Proteins and Puromycin Peptides to Proteolysis in vitro

Following incubation of Escherichia coli with puromycin hydrochloride increased proteolysis was detected both in vivo and in vitro. Cell fractionation showed that puromycin-stimulated proteolysis occurred primarily in the 150000 ×g supernatant fraction. Incubation with canavanine sulphate also gave rise to stimulated proteolysis in vivo but little proteolysis was detected when cell-free extracts of these cells were prepared. It is suggested that degradation of canavanyl proteins (proteins of normal length but altered composition) involves at least one step which is not involved in the degradation of at least some puromycin peptides which are presumably significantly shorter than normal gene products.