The three-dimensional structure of NAD(P)H:quinone reductase a flavoprotein involved in cancer chemoprotection and chemotherapy: Mechanism of the two-electron reduction

Rongbao Li, Mario A. Bianchet, Paul Talalay, L. Mario Amzel

Research output: Contribution to journalArticlepeer-review

Abstract

Quinone reductase [NAD(P)H:(quinone acceptor) oxidoreductase, EC 1.6.99.2], also called DT diaphorase, is a homodimeric FAD-containing enzyme that catalyzes obligatory NAD(P)H-dependent two-electron reductions of quinones and protects cells against the toxic and neoplastic effects of free radicals and reactive oxygen species arising from one-electron reductions. These two-electron reductions participate in the reductive bioactivation of cancer chemotherapeutic agents such as mitomycin C in tumor cells. Thus, surprisingly, the same enzymatic reaction that protects normal cells activates cytotoxic drugs used in cancer chemotherapy. The 2.1-Å crystal structure of rat liver quinone reductase reveals that the folding of a portion of each monomer is similar to that of flavodoxin, a bacterial FMN-containing protein. Two additional portions of the polypeptide chains are involved in dimerization and in formation of the two identical catalytic sites to which both monomers contribute. The crystallographic structures of two FAD-containing enzyme complexes (one containing NADP+, the other containing duroquinone) suggest that direct hydride transfers from NAD(P)H to FAD and from FADH2 to the quinone [which occupies the site vacated by NAD(P)H] provide a simple rationale for the obligatory two-electron reductions involving a ping-pong mechanism.

Original languageEnglish (US)
Pages (from-to)8846-8850
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume92
Issue number19
DOIs
StatePublished - Sep 12 1995

Keywords

  • Flavin
  • X-ray diffraction

ASJC Scopus subject areas

  • General

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