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. a quinone + 5 H(+)(in) + NADH = a quinol + 4 H(+)(out) + NAD(+) Binds 1 [2Fe-2S] cluster per subunit. The [2Fe-2S] cluster 1 is referred to as N1b. Binds 3 [4Fe-4S] clusters per subunit. The [4Fe-4S] clusters 2, 3, and 4 are referred to as N5, N4, and N7, respectively. The [4Fe-4S] cluster 4 is too far away from the main redox chain to participate in electron transfer but probably confers structural stability. 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 comprises two main parts, an N-terminal [FeFe]-hydrogenase-like domain (residues 1 to 240) that coordinates clusters 1, 2 and 3, and a domain similar to molybdopterin-containing enzymes (residues 241 to 767) whose first subdomain coordinates cluster 4. Belongs to the complex I 75 kDa subunit family.