Binds and transfers iron-sulfur (Fe-S) clusters to target apoproteins (PubMed:18616280, PubMed:19001370). Can hydrolyze ATP (PubMed:12486045, PubMed:19001370). Both activities are required for function in vivo, but the ability to hydrolyze ATP is not necessary for Fe-S cluster transfer (PubMed:19001370). Homodimer. Holo-ApbC forms a mixture of homodimers and homotetramers. Mutants are impaired in Fe-S cluster metabolism. They are conditional thiamine auxotrophs and have lower aconitase and succinate dehydrogenase activities. Belongs to the Mrp/NBP35 ATP-binding proteins family.