NADPH-dependent reductase which is a central component of the cytosolic iron-sulfur (Fe-S) protein assembly (CIA) machinery. 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. In turn, this reduced cluster provides electrons for assembly of cytosolic iron-sulfur cluster proteins. It can also reduce the [2Fe-2S] cluster of CISD1 and activate this protein implicated in Fe/S cluster repair (By similarity). In vitro can fully activate methionine synthase/MTR in the presence of soluble cytochrome b5/CYB5A (By similarity). NADPH + 2 oxidized [2Fe-2S]-[protein] = H(+) + NADP(+) + 2 reduced [2Fe-2S]-[protein] Interacts with CIAPIN1; as part of the cytosolic iron-sulfur (Fe-S) protein assembly (CIA) machinery (By similarity). Interacts with DCPS (By similarity). Concentrated in perinuclear structure. Belongs to the NADPH-dependent diflavin oxidoreductase NDOR1 family. In the N-terminal section; belongs to the flavodoxin family. In the C-terminal section; belongs to the flavoprotein pyridine nucleotide cytochrome reductase family.