FUNCTION Carrier of the growing fatty acid chain in fatty acid biosynthesis (By similarity) (PubMed:27626371). Accessory and non-catalytic subunit of the mitochondrial membrane respiratory chain NADH dehydrogenase (Complex I), which functions in the transfer of electrons from NADH to the respiratory chain (PubMed:27626371). Accessory protein, of the core iron-sulfur cluster (ISC) assembly complex, that regulates, in association with LYRM4, the stability and the cysteine desulfurase activity of NFS1 and participates in the [2Fe-2S] clusters assembly on the scaffolding protein ISCU (PubMed:31664822). The core iron-sulfur cluster (ISC) assembly complex is involved in the de novo synthesis of a [2Fe-2S] cluster, the first step of the mitochondrial iron-sulfur protein biogenesis. This process is initiated by the cysteine desulfurase complex (NFS1:LYRM4:NDUFAB1) that produces persulfide which is delivered on the scaffold protein ISCU in a FXN-dependent manner. Then this complex is stabilized by FDX2 which provides reducing equivalents to accomplish the [2Fe-2S] cluster assembly. Finally, the [2Fe-2S] cluster is transferred from ISCU to chaperone proteins, including HSCB, HSPA9 and GLRX5 (By similarity).SUBUNIT Mammalian complex I is composed of 45 different subunits (PubMed:12611891). Interacts with ETFRF1 (PubMed:27499296). Identified in a complex composed of MALSU1, MIEF1 upstream open reading frame protein and NDUFAB1; within the trimeric complex, MIEF1 upstream open reading frame protein functions as a bridging scaffold that interacts with MALSU1 on one side, and with NDUFAB1 on the other side. The complex interacts with the mitochondrial large ribosomal subunit (PubMed:28892042, PubMed:30215512, PubMed:35177605). Interacts with alpha-1-microglobulin chain; this interaction is required for the maintenance of mitochondrial redox homeostasis. Component of the mitochondrial core iron-sulfur cluster (ISC) complex composed of NFS1, LYRM4, NDUFAB1, ISCU, FXN, and FDX2; this complex is a heterohexamer containing two copies of each monomer (Probable). Component of the cyteine desulfurase complex composed of NFS1, LYRM4 and NDUFAB1; this complex contributes to the stability and cysteine desulfurase activity of NFS1 (PubMed:31664822).INTERACTION Phosphopantetheinylation at Ser-112 is essential for interactions with LYR motif-containing proteins.MISCELLANEOUS In contrast to other accessory subunits of complex I, NDUFAB1 is the only subunit that is essential for cell viability in HEK293T cells. Since knockout cells lack assembled complex I and die in galactose media, this suggests that the essential role of NDUFAB1 is independent of complex I.SIMILARITY Belongs to the acyl carrier protein (ACP) family.SEQUENCE CAUTION Extended N-terminus.