title: A DNA element recognised by the molybdenum-responsive transcription factor ModE is conserved in Proteobacteria, green sulphur bacteria and Archaea.
abstract: BACKGROUND
  The transition metal molybdenum is essential for life. Escherichia coli imports this metal into the cell in the form of molybdate ions, which are taken up via an ABC transport system. In E. coli and other Proteobacteria molybdenum metabolism and homeostasis are regulated by the molybdate-responsive transcription factor ModE.
  
  
  RESULTS
  Orthologues of ModE are widespread amongst diverse prokaryotes, but not ubiquitous. We identified probable ModE-binding sites upstream of genes implicated in molybdenum metabolism in green sulphur bacteria and methanogenic Archaea as well as in Proteobacteria. We also present evidence of horizontal transfer of nitrogen fixation genes between green sulphur bacteria and methanogenic Archaea.
  
  
  CONCLUSIONS
  Whereas most of the archaeal helix-turn-helix-containing transcription factors belong to families that are Archaea-specific, ModE is unusual in that it is found in both Archaea and Bacteria. Moreover, its cognate upstream DNA recognition sequence is also conserved between Archaea and Bacteria, despite the fundamental differences in their core transcription machinery. ModE is the third example of a transcriptional regulator with a binding signal that is conserved in Bacteria and Archaea.
authors.affiliation: Wellcome Trust Sanger Institute, Hinxton, Cambridge, CB10 1SA, UK. ds2@sanger.ac.uk
authors.forename: David J
authors.initials: DJ
authors.lastname: Studholme
authors.forename: Richard N
authors.initials: RN
authors.lastname: Pau
mesh_terms: D001105:Archaea / Q000235:genetics*; D001426:Bacterial Proteins; D001483:Base Sequence; D001665:Binding Sites; D019414:Chlorobi / Q000235:genetics*; D017124:Conserved Sequence; D019641:DNA, Archaeal / Q000378:metabolism; D004269:DNA, Bacterial / Q000378:metabolism; D029968:Escherichia coli Proteins; D008982:Molybdenum / Q000378:metabolism; D020560:Proteobacteria / Q000235:genetics*; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D019641:DNA, Archaeal; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; C491064:ModE protein, E coli; C101050:ModE protein, bacteria; D014157:Transcription Factors; C044659:molybdate; D008982:Molybdenum