1xcb | pdb_00001xcb

File:1xcb.jpg

spinqualitylabelsall models 1xcb, resolution 2.9Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D

X-ray Structure of a Rex-Family Repressor/NADH Complex from Thermus Aquaticus

Overview

The redox-sensing repressor Rex regulates transcription of respiratory genes in response to the intra cellular NADH/NAD(+) redox poise. As a step toward elucidating the molecular mechanism of NADH/NAD(+) sensing, the X-ray structure of Thermus aquaticus Rex (T-Rex) bound to effector NADH has been determined at 2.9 A resolution. The fold of the C-terminal domain of T-Rex is characteristic of NAD(H)-dependent enzymes, whereas the N-terminal domain is similar to a winged helix DNA binding motif. T-Rex dimerization is primarily mediated by "domain-swapped" alpha helices. Each NADH molecule binds to the C-terminal domain near the dimer interface. In contrast to NAD(H)-dependent enzymes, the nicotinamide is deeply buried within a hydrophobic pocket that appears to preclude substrate entry. We show that T-Rex binds to the Rex operator, and NADH but not NAD(+) inhibits T-Rex/DNA binding activity. A mechanism for redox sensing by Rex family members is proposed by analogy with domain closure of NAD(H)-dependent enzymes.

About this Structure

1XCB is a Single protein structure of sequence from Thermus aquaticus with CA and NAD as ligands. This structure supersedes the now removed PDB entry 1R72. Full crystallographic information is available from OCA.

Reference

X-ray structure of a Rex-family repressor/NADH complex insights into the mechanism of redox sensing., Sickmier EA, Brekasis D, Paranawithana S, Bonanno JB, Paget MS, Burley SK, Kielkopf CL, Structure. 2005 Jan;13(1):43-54. PMID:15642260

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