Core subunit of the mitochondrial membrane respiratory chain NADH dehydrogenase (Complex I) which catalyzes electron transfer from NADH through the respiratory chain, using ubiquinone as an electron acceptor (PubMed:14729820, PubMed:30140060). Essential for the catalytic activity and assembly of complex I (PubMed:14729820, PubMed:24028823, PubMed:30140060). a ubiquinone + 5 H(+)(in) + NADH = a ubiquinol + 4 H(+)(out) + NAD(+) Core subunit of respiratory chain NADH dehydrogenase (Complex I) which is composed of 45 different subunits (PubMed:12611891). Interacts with NDUFAF3 (PubMed:19463981). Interacts with RAB5IF (PubMed:31536960). Found in subcomplexes containing subunits NDUFS2, MT-ND1 and NDUFA13 (PubMed:17209039, PubMed:18826940). The disease is caused by variants affecting the gene represented in this entry. Belongs to the complex I 30 kDa subunit family.