PMID: 20513431 , Related PDB ids: 3IKT, 3IKV, 3IL2

Authors:

McLaughlin KJ, Strain-Damerell CM, Xie K, Brekasis D, Soares AS, Paget MS, Kielkopf CL

Title:

Structural basis for NADH/NAD+ redox sensing by a Rex family repressor.

Journal:

Mol Cell. 2010 May 28;38(4):563-75.

Abstract:

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.