Structural Basis for Inhibition of ROS-Producing Respiratory Complex I by NADH-OH.

NADH:ubiquinone oxidoreductase, respiratory complex I, plays a central role in cellular energy metabolism. As a major source of reactive oxygen species (ROS) it affects ageing and mitochondrial dysfunction. The novel inhibitor NADH-OH specifically blocks NADH oxidation and ROS production by complex I in nM concentrations. Attempts to elucidate its structure by NMR failed. Here, we report by X-ray crystallographic analysis the structure of NADH-OH bound in the active site of a soluble fragment of complex I at 2.0 A resolution. We have identified key amino acid residues specific and essential for binding NADH-OH. Furthermore, the structure sheds light on the specificity of NADH-OH towards the unique Rossmann-fold of complex I and indicates a regulatory role for mitochondrial ROS generation. In addition, NADH-OH displays a lead-structure for synthesis of a novel class of ROS suppressors.