AAA proteases of mitochondria: quality control of membrane proteins and regulatory functions during mitochondrial biogenesis

An ubiquitous and conserved proteolytic regulates the stability of mitochon drial inner membrane proteins. Two AAA proteases,vith catalytic sites at op posite membrane surfaces form a membrane-integrated quality control system and exert crucial functions during the biogenesis of mitochondria. Their ac tivity is modulated by another membrane-protein complex that is composed of prohibitins. Peptides generated upon proteolysis in the matrix space are t ransported across the inner membrane by an ATP-binding cassette transporter . The function of these conserved components is discussed in the present re view.