1XI2: Quinone Reductase 2 In Complex With Cancer Prodrug Cb1954

CB1954 is a cancer pro-drug that can be activated through reduction by Escherichia coli nitro-reductases and quinone reductases. Human quinone reductase 2 is very efficient in the activation of CB1954, approximately 3000 times more efficient than human QR1 in terms of k(cat)/K(m). We have solved the three-dimensional structure of QR2 in complex with CB1954 to a nominal resolution of 1.5A. The complex structure indicates the essentiality of the two nitro groups: one nitro group forms hydrogen bonds with the side-chain of Asn161 of QR2 to hold the other nitro group in position for the reduction. We further conclude that residue 161, an Asn in QR2 and a His in QR1, is critical in differentiating the substrate specificities of these two enzymes. Mutation of Asn161 to His161 in QR2 resulted in the total loss of the enzymatic activity towards activation of CB1954, whereas the rates of reduction towards menadione are not altered.
PDB ID: 1XI2Download
MMDB ID: 34647
PDB Deposition Date: 2004/9/21
Updated in MMDB: 2007/10
Experimental Method:
x-ray diffraction
Resolution: 1.5  Å
Source Organism:
Similar Structures:
Biological Unit for 1XI2: dimeric; determined by author and by software (PISA)
Molecular Components in 1XI2
Label Count Molecule
Proteins (2 molecules)
NRH Dehydrogenase [quinone] 2(Gene symbol: NQO2)
Molecule annotation
Chemicals (7 molecules)
* Click molecule labels to explore molecular sequence information.

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