Protease that is part of the quality control system in the inner membrane of mitochondria (By similarity). Cleaves and thereby promotes the turnover of mistranslated or misfolded membrane protein (By similarity). Required for TOR signaling (PubMed:27325672). Binds 1 zinc ion per subunit. Protease activity is induced in response to various mitochondrial stress. Cells are resistant to rapamycin and display reduced TOR signaling. Belongs to the peptidase M48 family.