Degradation of abnormal proteins in Escherichia coli (protein breakdown-protein structure-mistranslation-amino acid analogs-puromycin).

Evidence is presented that E. coli contains a mechanism for selective degradation of abnormal proteins. Unfinished polypeptides containing puromycin, proteins containing frequent errors in translation, such as those synthesized by strains containing a ram mutation or a missense suppressor, and proteins containing amino-acid analogs were degraded more rapidly than were normal cell proteins. The degradation of analog- or puromycin-containing proteins appears to be an energy-dependent process. Unlike normal proteins, such proteins were degraded at similar rates by growing and by nongrowing cells.