Component of the mitochondrial inner membrane i-AAA protease supercomplex required for mitochondrial inner membrane protein turnover. Together with MGR3, functions in an adapter complex that targets substrates to the i-AAA protease for degradation. Required for growth of cells lacking the mitochondrial genome. Component of the mitochondrial inner membrane i-AAA protease supercomplex composed of MGR1, MGR3 and YME1. With MGR3, forms a subcomplex that binds to YME1 and to substrates to facilitate proteolysis. Interacts directly with YME1. Present with 3410 molecules/cell in log phase SD medium. Belongs to the MGR1 family.