X-ray structure of a Rex-family repressor/NADH complex insights into the mechanism of redox sensing

E. Allen Sickmier, Dimitris Brekasis, Shanthi Paranawithana, Jeffrey B. Bonanno, Mark S.B. Paget, Stephen K. Burley, Clara L. Kielkopf

Research output: Contribution to journalArticle

62 Scopus citations

Abstract

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 Å 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" α 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.

Original languageEnglish (US)
Pages (from-to)43-54
Number of pages12
JournalStructure
Volume13
Issue number1
DOIs
StatePublished - Jan 1 2005
Externally publishedYes

ASJC Scopus subject areas

  • Structural Biology
  • Molecular Biology

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    Sickmier, E. A., Brekasis, D., Paranawithana, S., Bonanno, J. B., Paget, M. S. B., Burley, S. K., & Kielkopf, C. L. (2005). X-ray structure of a Rex-family repressor/NADH complex insights into the mechanism of redox sensing. Structure, 13(1), 43-54. https://doi.org/10.1016/j.str.2004.10.012