The crystal structure of the TetR family transcriptional repressor SimR bound to DNA and the role of a flexible N-terminal extension in minor groove binding.

Published

Journal Article

SimR, a TetR-family transcriptional regulator (TFR), controls the export of simocyclinone, a potent DNA gyrase inhibitor made by Streptomyces antibioticus. Simocyclinone is exported by a specific efflux pump, SimX and the transcription of simX is repressed by SimR, which binds to two operators in the simR-simX intergenic region. The DNA-binding domain of SimR has a classical helix-turn-helix motif, but it also carries an arginine-rich N-terminal extension. Previous structural studies showed that the N-terminal extension is disordered in the absence of DNA. Here, we show that the N-terminal extension is sensitive to protease cleavage, but becomes protease resistant upon binding DNA. We demonstrate by deletion analysis that the extension contributes to DNA binding, and describe the crystal structure of SimR bound to its operator sequence, revealing that the N-terminal extension binds in the minor groove. In addition, SimR makes a number of sequence-specific contacts to the major groove via its helix-turn-helix motif. Bioinformatic analysis shows that an N-terminal extension rich in positively charged residues is a feature of the majority of TFRs. Comparison of the SimR-DNA and SimR-simocyclinone complexes reveals that the conformational changes associated with ligand-mediated derepression result primarily from rigid-body rotation of the subunits about the dimer interface.

Full Text

Duke Authors

Cited Authors

  • Le, TBK; Schumacher, MA; Lawson, DM; Brennan, RG; Buttner, MJ

Published Date

  • November 2011

Published In

Volume / Issue

  • 39 / 21

Start / End Page

  • 9433 - 9447

PubMed ID

  • 21835774

Pubmed Central ID

  • 21835774

Electronic International Standard Serial Number (EISSN)

  • 1362-4962

International Standard Serial Number (ISSN)

  • 0305-1048

Digital Object Identifier (DOI)

  • 10.1093/nar/gkr640

Language

  • eng