Negative regulator of the mitochondrial respiratory chain. Prevents mitochondrial hyperpolarization state and restricts mitochondrial generation of ATP (By similarity). Acts as an import component of the TIM23 translocase complex. Stimulates the ATPase activity of HSPA9. Interacts with the TIM23 complex. Directly interacts with PAM16/MAGMAS; this interaction counteracts DNAJC15-dependent stimulation of HSPA9 ATPase activity. Associates with complex I of the mitochondrial electron transfer chain; this interaction may interfere with the formation of supercomplexes that facilitate the transfer of electrons between complexes (By similarity). Expressed at highest levels in heart, followed by liver and kidney. Absent or down-regulated in many advanced cases of ovarian adenocarcinoma, due to hypermethylation and allelic loss. Loss of expression correlates with increased resistance to antineoplastic drugs, such as cisplatin.