Associates in vitro with the adrenodoxin reductase MFDR to form an efficient low potential electron transfer chain that is able to reduce cytochrome C (PubMed:12714594, PubMed:13677469). Functions as accessory mitochondrial protein involved with BIO2 in the plant biotin synthase reaction (PubMed:12714594). Binds 1 [2Fe-2S] cluster. Belongs to the adrenodoxin/putidaredoxin family.