This protein, Nqo15, is a part of respiratory complex 1 which is a complex that plays a central role in cellular energy production in both bacteria and mitochondria. Nqo15 has a similar fold to Frataxin, the mitochondrial iron chaperone. This protein may have a role in iron-sulphur cluster regeneration in the complex. This domain represents more than half the molecular mass of the entire complex [1].

1: Structure of the hydrophilic domain of respiratory complex I from Thermus thermophilus. Sazanov LA, Hinchliffe P; Science. 2006;311:1430-1436. PMID:16469879