Acts as a processive, ATP-dependent zinc metallopeptidase for both cytoplasmic and membrane proteins. Plays a role in the quality control of integral membrane proteins. Binds 1 zinc ion per subunit. Homohexamer. Not essential for growth. A number of proteins can be seen to be more stable in the disruption mutants, suggesting some of them may be substrates for the protease. In the central section; belongs to the AAA ATPase family. In the C-terminal section; belongs to the peptidase M41 family. Extended N-terminus.