NADPH-dependent reductase which is a central component of the cytosolic iron-sulfur (Fe-S) protein assembly (CIA) machinery (PubMed:10625700, PubMed:28648056, PubMed:23596212, PubMed:20802492, PubMed:15900210). 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:28648056, PubMed:23596212, PubMed:20802492). In turn, this reduced cluster provides electrons for assembly of cytosolic iron-sulfur cluster proteins (PubMed:23596212, PubMed:20802492). 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). NADPH + 2 oxidized [2Fe-2S]-[protein] = H(+) + NADP(+) + 2 reduced [2Fe-2S]-[protein] Optimum pH is about 8.0. E(0) is -315 +/- 5 mV for the FAD oxidized/semiquinone couple, E(0) is -365 +/- 15 mV for the FAD semiquinone/dihydroquinone couple, E(0) is -146 +/- 5 mV for the FMN oxidized/semiquinone couple, and E(0) is -305 +/- 5 mV for the FMN semiquinone/dihydroquinone couple. Interacts with CIAPIN1; as part of the cytosolic iron-sulfur (Fe-S) protein assembly (CIA) machinery (By similarity) (PubMed:20802492, PubMed:23596212). Interacts with DCPS (PubMed:16140270). Concentrated in perinuclear structure. Low expression in brain, heart, kidney, pancreas, prostate and skeletal muscle. Highest levels in the placenta. Expressed in cancer cell lines including promyelocytic leukemia, HeLaS3, chronic myelagenous leukemia, lymphoblastic leukemia, Burkitt's lymphoma, colorectal adenocarcinoma, lung carcinoma, and melanoma G-361. 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.