ATP-dependent serine protease that mediates the selective degradation of mutant and abnormal proteins as well as certain short-lived regulatory proteins. Required for cellular homeostasis and for survival from DNA damage and developmental changes induced by stress. Degrades polypeptides processively to yield small peptide fragments that are 5 to 10 amino acids long. Binds to DNA in a double-stranded, site-specific manner. Endogenous substrates include the regulatory proteins RcsA and SulA, the transcriptional activator SoxS, and UmuD. Its overproduction specifically inhibits translation through at least two different pathways, one of them being the YoeB-YefM toxin-antitoxin system. Hydrolysis of proteins in presence of ATP. Contains an allosteric site (distinct from its active site), whose occupancy by an unfolded polypeptide leads to enzyme activation. Homohexamer. Organized in a ring with a central cavity. ATP binding and hydrolysis do not affect the oligomeric state of the enzyme. By accumulation of abnormal proteins, such as at high temperatures. Under stress conditions. Belongs to the peptidase S16 family. Extended N-terminus.