NQO9_THET8 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 role of the nqo9 subunit appears to provide a 'connecting chain' of two clusters between cluster N5 and the terminal cluster N2, and to stabilize the structure of the complex by interacting with other subunits. NADH-quinone oxidoreductase subunit 9 nqo9 NDH-1 subunit 9 182 MTLKALAQSLGITLKYLFSKPVTVPYPDAPVALKPRFHGRHVLTRHPNGLEKCIGCSLCAAACPAYAIYVEPAENDPENPVSAGERYAKVYEINMLRCIFCGLCEEACPTGAIVLGYDFEMADYEYSDLVYGKEDMLVDVVGTKPQRREAKRTGKPVKVGYVVPYVRPELEGFKAPTEGGKR TTHA0092 NADH dehydrogenase I subunit 9