Structures of recombinant human and mouse NAD(P)H:quinone oxidoreductases: Species comparison and structural changes with substrate binding and release

AUTOR(ES)

Faig, Margarita

FONTE

The National Academy of Sciences

RESUMO

NAD(P)H/quinone acceptor oxidoreductase (QR1, NQO1, formerly DT-diaphorase; EC 1.6.99.2) protects animal cells from the deleterious and carcinogenic effects of quinones and other electrophiles. In this paper we report the apoenzyme structures of human (at 1.7-Å resolution) and mouse (2.8 Å) QR1 and the complex of the human enzyme with the substrate duroquinone (2.5 Å) (2,3,5,6-tetramethyl-p-benzoquinone). In addition to providing a description and rationale of the structural and catalytic differences among several species, these structures reveal the changes that accompany substrate or cofactor (NAD) binding and release. Tyrosine-128 and the loop spanning residues 232–236 close the binding site, partially occupying the space left vacant by the departing molecule (substrate or cofactor). These changes highlight the exquisite control of access to the catalytic site that is required by the ping-pong mechanism in which, after reducing the flavin, NAD(P)+ leaves the catalytic site and allows substrate to bind at the vacated position. In the human QR1-duroquinone structure one ring carbon is significantly closer to the flavin N5, suggesting a direct hydride transfer to this atom.

Documentos Relacionados

• New Insights into Type II NAD(P)H:Quinone Oxidoreductases
• Subunit functional studies of NAD(P)H:quinone oxidoreductase with a heterodimer approach.
• Unexpected genetic and structural relationships of a long-forgotten flavoenzyme to NAD(P)H:quinone reductase (DT-diaphorase)
• Dissecting the Diphenylene Iodonium-Sensitive NAD(P)H:Quinone Oxidoreductase of Zucchini Plasma Membrane.
• p53 hot-spot mutants are resistant to ubiquitin-independent degradation by increased binding to NAD(P)H:quinone oxidoreductase 1