Plays a key role in regulating maximal capacity for electron transport and oxidative phosphorylation. May be involved in Fe-S cluster shuttling and/or in redox reactions (By similarity). Binds 1 [2Fe-2S] cluster per subunit. Homodimer. Liver, adipose, skeletal muscle and heart (at protein level). Widely expressed. Expressed at the highest levels in the heart. Ubiquitinated by PRKN during mitophagy, leading to its degradation and enhancement of mitophagy. Deubiquitinated by USP30. Belongs to the CISD protein family.