Accessory subunit of the mitochondrial membrane respiratory chain NADH dehydrogenase (Complex I), that is believed not to be involved in catalysis. Complex I functions in the transfer of electrons from NADH to the respiratory chain. The immediate electron acceptor for the enzyme is believed to be ubiquinone. Involved in the interferon/all-trans-retinoic acid (IFN/RA) induced cell death. This apoptotic activity is inhibited by interaction with viral IRF1. Prevents the transactivation of STAT3 target genes. May play a role in CARD15-mediated innate mucosal responses and serve to regulate intestinal epithelial cell responses to microbes. Complex I is composed of 45 different subunits. Interacts with CARD15, but not with CARD4. Interacts with STAT3, but not with STAT1, STAT2 and STAT5A. Interacts with OLFM4. Localizes mainly in the mitochondrion. May be translocated into the nucleus upon IFN/RA treatment. Belongs to the complex I NDUFA13 subunit family.