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 Nqo4 subunit may contain the quinone-binding site. a quinone + 5 H(+)(in) + NADH = a quinol + 4 H(+)(out) + NAD(+) 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. This subunit interacts extensively with Nqo6. Belongs to the complex I 49 kDa subunit family.