期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 97, 期 7, 页码 3177-3182出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.050585797
关键词
DT diaphorase; cancer; chemoprotection; chemotherapy
资金
- NCI NIH HHS [CA 51210, CA 44530, R01 CA051210] Funding Source: Medline
- NIGMS NIH HHS [GM51362] Funding Source: Medline
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-Angstrom resolution) and mouse (2.8 Angstrom) QR1 and the complex of the human enzyme with the substrate duroquinone (2.5 Angstrom) (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.
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