The mechanism of catalysis by type-II NADH:quinone oxidoreductases.

TitleThe mechanism of catalysis by type-II NADH:quinone oxidoreductases.
Publication TypeJournal Article
Year of Publication2017
AuthorsBlaza, JN, Bridges, HR, Aragão, D, Dunn, EA, Heikal, A, Cook, GM, Nakatani, Y, Hirst, J
JournalSci Rep
Volume7
Pagination40165
Date Published2017 Jan 09
ISSN2045-2322
Abstract

Type II NADH:quinone oxidoreductase (NDH-2) is central to the respiratory chains of many organisms. It is not present in mammals so may be exploited as an antimicrobial drug target or used as a substitute for dysfunctional respiratory complex I in neuromuscular disorders. NDH-2 is a single-subunit monotopic membrane protein with just a flavin cofactor, yet no consensus exists on its mechanism. Here, we use steady-state and pre-steady-state kinetics combined with mutagenesis and structural studies to determine the mechanism of NDH-2 from Caldalkalibacillus thermarum. We show that the two substrate reactions occur independently, at different sites, and regardless of the occupancy of the partner site. We conclude that the reaction pathway is determined stochastically, by the substrate/product concentrations and dissociation constants, and can follow either a ping-pong or ternary mechanism. This mechanistic versatility provides a unified explanation for all extant data and a new foundation for the development of therapeutic strategies.

DOI10.1038/srep40165
Alternate JournalSci Rep
Citation Key10.1038/srep40165
PubMed ID28067272
PubMed Central IDPMC5220320
Grant ListMC_U105663141 / / Medical Research Council / United Kingdom