X-ray structure of a Rex-family repressor/NADH complex insights into the mechanism of redox sensing
| Autor: | E. Allen Sickmier, Dimitris Brekasis, Mark S. B. Paget, Shanthi R. Paranawithana, Clara L. Kielkopf, Jeffrey B. Bonanno, Stephen K. Burley |
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| Rok vydání: | 2004 |
| Předmět: |
Models
Molecular Stereochemistry Protein Conformation viruses Amino Acid Motifs Molecular Sequence Data Repressor Electrophoretic Mobility Shift Assay Winged Helix Crystallography X-Ray Redox Cofactor Protein Structure Secondary Structural Biology Operon Escherichia coli Amino Acid Sequence Thermus Molecular Biology Conserved Sequence chemistry.chemical_classification Binding Sites biology Thermus aquaticus Sequence Homology Amino Acid Effector DNA biochemical phenomena metabolism and nutrition Surface Plasmon Resonance biology.organism_classification NAD Protein Structure Tertiary Gene Products rex Repressor Proteins Enzyme chemistry biology.protein NAD+ kinase Dimerization Hydrophobic and Hydrophilic Interactions Oxidation-Reduction |
| Zdroj: | Structure (London, England : 1993). 13(1) |
| ISSN: | 0969-2126 |
| Popis: | 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. |
| Databáze: | OpenAIRE |
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