Negative Cooperativity in NAD(P)H Quinone Oxidoreductase 1 (NQO1)

NAD(P)H quinone oxidoreductase‐1 (NQO1) is a homodimeric protein that acts as a detoxifying enzyme or as a chaperone protein. Dicourmarol interacts with NQO1 at the NAD(P)H binding site and can both inhibit enzyme activity and modulate the interaction of NQO1 with other proteins. We show that the binding of dicoumarol and related compounds to NQO1 generates negative cooperativity between the monomers. This does not occur in the presence of the reducing cofactor, NAD(P)H, alone. Alteration of Gly150 (but not Gly149 or Gly174) abolished the dicoumarol‐induced negative cooperativity. Analysis of the dynamics of NQO1 with the Gaussian network model indicates a high degree of collective motion by monomers and domains within NQO1. Ligand binding is predicted to alter NQO1 dynamics both proximal to the ligand binding site and remotely, close to the second binding site. Thus, drug‐induced modulation of protein motion might contribute to the biological effects of putative inhibitors of NQO1. Proposing the motion: The flavoprotein NQO1 demonstrates negative cooperativity towards a competitive inhibitor, dicoumarol. A Gaussian network model suggests that this arises from a high degree of collective motion within the protein. These findings have implications for understanding NQO1′s cellular roles and in the discovery of anticancer drugs that target the enzyme.