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Title: DNA Recognition by a σ54 Transcriptional Activator from Aquifex aeolicus

Transcription initiation by bacterial σ54-polymerase requires the action of a transcriptional activator protein. Activators bind sequence-specifically upstream of the transcription initiation site via a DNA-binding domain. The structurally characterized DNA-binding domains from activators all belong to the Factor for Inversion Stimulation (Fis) family of helix-turn-helix DNA-binding proteins. We report here structures of the free and DNA-bound forms of the DNA-binding domain of NtrC4 (4DBD) from Aquifex aeolicus, a member of the NtrC family of σ54 activators. Two NtrC4 binding sites were identified upstream (-145 and -85 base pairs) from the start of the lpxC gene, which is responsible for the first committed step in Lipid A biosynthesis. This is the first experimental evidence for σ54 regulation in lpxC expression. 4DBD was crystallized both without DNA and in complex with the -145 binding site. The structures, together with biochemical data, indicate that NtrC4 binds to DNA in a manner that is similar to that of its close homologue, Fis. Ultimately, the greater sequence specificity for the binding of 4DBD relative to Fis seems to arise from a larger number of base specific contacts contributing to affinity than for Fis.
 [1] ;  [1] ;  [1] ;  [1] ;  [2] ;  [3] ;  [1] ;  [2] ;  [1] ;  [4]
  1. Univ. of California, Berkeley, CA (United States)
  2. Univ. of California, Los Angeles, CA (United States)
  3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  4. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Publication Date:
OSTI Identifier:
Grant/Contract Number:
AC02-05CH11231; FG05-86ER75281
Accepted Manuscript
Journal Name:
Journal of Molecular Biology
Additional Journal Information:
Journal Volume: 426; Journal Issue: 21; Journal ID: ISSN 0022-2836
Research Org:
Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
59 BASIC BIOLOGICAL SCIENCES DNA complex; DNA-binding domain; sequence-specific recognition; NtrC; Fis