NDH-1 shuttles electrons from NADH, via FMN and iron-sulfur (Fe-S) centers, to quinones in the respiratory chain. The immediate electron acceptor for the enzyme in this species is menaquinone. Couples the redox reaction to proton translocation (for every two electrons transferred, four hydrogen ions are translocated across the cytoplasmic membrane), and thus conserves the redox energy in a proton gradient required for the synthesis of ATP. The Nqo1 subunit contains the NADH-binding site and the primary electron acceptor FMN. a quinone + 5 H(+)(in) + NADH = a quinol + 4 H(+)(out) + NAD(+) Binds 1 FMN per subunit. Binds 1 [4Fe-4S] cluster per subunit. This [4Fe-4S] cluster is referred to as N3. NDH-1 is composed of 15 different subunits, Nqo1 to Nqo15. The complex has a L-shaped structure, with the hydrophobic arm (subunits Nqo7, Nqo8 and Nqo10 to Nqo14) embedded in the membrane and the hydrophilic peripheral arm (subunits Nqo1 to Nqo6, Nqo9 and Nqo15) protruding into the bacterial cytoplasm. The hydrophilic domain contains all the redox centers. The subunit can be separated roughly into four domains: an N-terminal domain (residues 7 to 72) ending with a glycine-rich loop, followed by a Rossman-fold domain (73 to 240), a ubiquitin-like domain (241 to 335) and a C-terminal four-helical bundle containing cluster N3 (336 to 438). Belongs to the complex I 51 kDa subunit family.