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PDBsum entry 3ikt
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DNA binding protein/DNA
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PDB id
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3ikt
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References listed in PDB file
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Key reference
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Title
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Structural basis for nadh/nad+ redox sensing by a rex family repressor.
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Authors
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K.J.Mclaughlin,
C.M.Strain-Damerell,
K.Xie,
D.Brekasis,
A.S.Soares,
M.S.Paget,
C.L.Kielkopf.
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Ref.
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Mol Cell, 2010,
38,
563-575.
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PubMed id
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Abstract
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Nicotinamide adenine dinucleotides have emerged as key signals of the cellular
redox state. Yet the structural basis for allosteric gene regulation by the
ratio of reduced NADH to oxidized NAD(+) is poorly understood. A key sensor
among Gram-positive bacteria, Rex represses alternative respiratory gene
expression until a limited oxygen supply elevates the intracellular NADH:NAD(+)
ratio. Here we investigate the molecular mechanism for NADH/NAD(+) sensing among
Rex family members by determining structures of Thermus aquaticus Rex bound to
(1) NAD(+), (2) DNA operator, and (3) without ligand. Comparison with the
Rex/NADH complex reveals that NADH releases Rex from the DNA site following a 40
degrees closure between the dimeric subunits. Complementary site-directed
mutagenesis experiments implicate highly conserved residues in NAD-responsive
DNA-binding activity. These rare views of a redox sensor in action establish a
means for slight differences in the nicotinamide charge, pucker, and orientation
to signal the redox state of the cell.
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