4U7F image
Deposition Date 2014-07-30
Release Date 2015-02-11
Last Version Date 2023-12-27
Entry Detail
PDB ID:
4U7F
Title:
Reduced quinone reductase 2 in complex with CK2 inhibitor DMAT
Biological Source:
Source Organism:
Homo sapiens (Taxon ID: 9606)
Host Organism:
Method Details:
Experimental Method:
Resolution:
1.80 Å
R-Value Free:
0.22
R-Value Work:
0.18
R-Value Observed:
0.18
Space Group:
P 21 21 21
Macromolecular Entities
Polymer Type:polypeptide(L)
Molecule:Ribosyldihydronicotinamide dehydrogenase [quinone]
Gene (Uniprot):NQO2
Chain IDs:A, B
Chain Length:230
Number of Molecules:2
Biological Source:Homo sapiens
Primary Citation
Quinone Reductase 2 Is an Adventitious Target of Protein Kinase CK2 Inhibitors TBBz (TBI) and DMAT.
Biochemistry 54 47 59 (2015)
PMID: 25379648 DOI: 10.1021/bi500959t

Abstact

Quinone reductase 2 (NQO2) exhibits off-target interactions with two protein kinase CK2 inhibitors, 4,5,6,7-1H-tetrabromobenzimidazole (TBBz) and 2-dimethylamino-4,5,6,7-tetrabromo-1H-benzimidazole (DMAT). TBBz and DMAT induce apoptosis in cells expressing an inhibitor-resistant CK2, suggesting that the interaction with NQO2 may mediate some of their pharmacological effects. In this study, we have fully characterized the binding of TBBz and DMAT to NQO2. Fluorescence titrations showed that TBBz and DMAT bind oxidized NQO2 in the low nanomolar range; in the case of TBBz, the affinity for NQO2 was 40-fold greater than its affinity for CK2. A related CK2 inhibitor, 4,5,6,7-tetrabromobenzotriazole (TBB), which failed to cause apoptosis in cells expressing inhibitor-resistant CK2, binds NQO2 with an affinity 1000-fold lower than those of TBBz and DMAT. Kinetic analysis indicated that DMAT inhibits NQO2 by binding with similar affinities to the oxidized and reduced forms. Crystal structure analysis showed that DMAT binds reduced NQO2 in a manner different from that in the oxidized state. In oxidized NQO2, TBBz and DMAT are deeply buried in the active site and make direct hydrogen and halogen bonds to the enzyme. In reduced NQO2, DMAT occupies a more peripheral region and hydrogen and halogen bonds with the enzyme are mediated through three water molecules. Therefore, although TBB, TBBz, and DMAT are all potent inhibitors of CK2, they exhibit different activity profiles toward NQO2. We conclude that the active site of NQO2 is fundamentally different from the ATP binding site of CK2 and the inhibition of NQO2 by CK2 inhibitors is adventitious.

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Primary Citation of related structures