Alternative, nonproton pumping NADH:quinone oxidoreductase that delivers electrons to the respiratory chain by oxidation of NADH and reduction of quinones, and contributes to the regeneration of NAD(+) (PubMed:26172206, PubMed:28801048). Can use DMN, a menaquinone analog, 2,3-dimethoxy-5,6-dimethyl-benzoquinone (DDB), an ubiquinone analog, or 2,3,5,6-tetramethyl-1,4-benzoquinone (Duroquinone, DQ) a plastoquinone analog as electron acceptors (PubMed:26172206). a quinone + H(+) + NADH = a quinol + NAD(+) a menaquinone + H(+) + NADH = a menaquinol + NAD(+) a ubiquinone + H(+) + NADH = a ubiquinol + NAD(+) Binds 1 FAD per subunit. Inhibited by HQNO, a quinone derivative. kcat is 67.9 sec(-1) with DMN as substrate. kcat is 69.4 sec(-1) with DDB as substrate. kcat is 68.2 sec(-1) with DQ as substrate. Homodimer in solution (PubMed:25849513, PubMed:26172206). Forms homotetramers; dimer of dimers (PubMed:25849513, PubMed:26172206). Interacts with the membrane via an anti-parallel three-stranded beta-sheet followed by two helices arranged in a helix-turn-helix motif at the C-terminal region. Contains a first dinucleotide binding domain, which harbors FAD, a second dinucleotide binding domain, which interacts with NADH and C-terminal domain that provides anchoring to the membrane (PubMed:28801048). A long discussion has taken place about whether NADH and the quinone bind to the same or to different sites. Structural studies clearly indicate the presence of distinct binding sites for the two substrates (PubMed:26172206, PubMed:28181562). Belongs to the NADH dehydrogenase family.