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

Abstract

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.

The Catalytic Cycle of the Antioxidant and Cancer-Associated Human NQO1 Enzyme: Hydride Transfer, Conformational Dynamics and Functional Cooperativity

“…The observed rate constants for this process, k obsA→B , showed hyperbolic dependence on NADH concentration ( Figure 4E), allowing for the determination of a NADH dissociation constant (K d NADH ), as well as of a limiting HT rate constant (k HT1 ), without considering the occurrence of any reverse HT reaction. The limiting value for k HT1 of 284 ± 17 s −1 (at 6 • C) indicates a very fast HT from NADH to NQO1 ox , which compares well with the steady-state catalytic constant (k cat ) of 180-200 s −1 (at 30-37 • C) [31,33,48]. This agreement supports that the HT process is the rate-limiting step within the reductive half-reaction.…”

Escherichia coli Modulator of Drug Activity B (MdaB) Has Different Enzymological Properties to Eukaryote Quinone Oxidoreductases

“…A communication pathway linking the active sites through changes in conformation and mobility has been computationally identified in human NQO1. [25] Structural alignment of MdaB with human NQO1 indicates the presence of an equivalent structure in MdaB. However, there are no residues within this pathway which match those in the pathway in NQO1.…”

“…[24] In human NQO1, glycine 150 has been identified as pivotal to the mechanism and a change from glycine to the more conformationally restricting residue serine at this position, largely abolished negative cooperativity. [25] MdaB was structurally aligned to human NQO1 (PDB 2F1O [26] ), and the equivalent residue to the pivotal glycine in NQO1 was identified as Ala-127 in MdaB. To investigate whether, or not, negative cooperativity towards inhibitors could be introduced into MdaB, this alanine was changed to glycine in order to increase conformational freedom and flexibility at this position.…”

Targeting HIF-1α Function in Cancer through the Chaperone Action of NQO1

“…Some of these may be undesirable in the context of cancer therapy, e.g. the antagonism of the NQO1/p53 interaction and consequent down-regulation of p53-mediated apoptosis [153,154].…”

“…[162] β-lapachone Futile cycling involving NQO1 results in reduced cellular concentrations of NAD(P)H contributing to cell death [163,164] Mitomycin C Reduction activates this akylating cytotoxic drug [165,166] Tirapazamine and other heteroaromatic N-oxides Slow reaction. Superoxide also produced [167] Benzofuroxans Reduction by NQO1 may play a minor role in cytotoxicity [168] Nitroaromatics Reactivity correlates with electrode potential [169,170] Aminochrome Reaction is important in protection against Parkinson's Disease and other neurological diseases [171,172] Inhibitors Dicoumarol and derivatives thereof High affinity; competes with NAD(P)H; negatively cooperative; often used in experimental studies; derivatives may be anticancer lead compounds; dissociates NQO1-p53 complexes resulting in increased p53 degradation and inhibition of apoptosis [143,151,154,156,173,174] Curcumin May dissociate NQO1-p53 complexes resulting in increased p53 degradation and inhibition of apoptosis. Other studies suggest it may enhance the NQO1-p53 interaction in vivo [175,176] Resveratrol Potent inhibitor of the related protein NQO2; only weakly inhibits NQO1 [177] Warfarin NQO1 is a secondary target for this anticoagulant [174,178] [190,191] Preprints (www.preprints.org) | NOT PEER-REVIEWED Interaction occurs in response to genotoxic stress.…”