Required for mitochondrial cristae morphogenesis and MGM1-processing. Controls the stability of mitochondrial phosphatidylethanolamine (PE). With UPS1, controls the level of cardiolipin in mitochondria. Cardiolipin is a unique phospholipid with four fatty acid chains and is present mainly in the mitochondrial inner membrane where it stabilizes the electron transport chain supercomplex between complexes III and IV through direct interaction of their subunits. Interacts with MDM35. Lacks the two major intermembrane space-targeting signals, bipartite presequences and cysteine motifs, and import is mediated by another IMS protein, MDM35. Defects in mitochondrial morphology. Present with 2910 molecules/cell in log phase SD medium. Belongs to the slowmo family.