NADPH-dependent reductase which is a central component of the cytosolic iron-sulfur (Fe-S) protein assembly (CIA) machinery (PubMed:10625700, PubMed:15900210, PubMed:20802492, PubMed:23596212, PubMed:28648056). Transfers electrons from NADPH via its FAD and FMN prosthetic groups to the [2Fe-2S] cluster of CIAPIN1, another key component of the CIA machinery (PubMed:20802492, PubMed:23596212, PubMed:28648056). In turn, this reduced cluster provides electrons for assembly of cytosolic iron-sulfur cluster proteins (PubMed:20802492, PubMed:23596212). It can also reduce the [2Fe-2S] cluster of CISD1 and activate this protein implicated in Fe/S cluster repair (PubMed:28648056). In vitro can fully activate methionine synthase/MTR in the presence of soluble cytochrome b5/CYB5A (PubMed:12871938).