Identification of the Acidobacterium capsulatum LexA box reveals a lateral acquisition of the Alphaproteobacteria lexA gene

Microbiology (Reading). 2006 Apr;152(Pt 4):1109-1118. doi: 10.1099/mic.0.28376-0.


Acidobacterium capsulatum is the most thoroughly studied species of a new bacterial phylogenetic group designated the phylum Acidobacteria. Through a tblastn search, the A. capsulatum lexA gene has been identified, and its product purified. Electrophoretic mobility shift assays have shown that A. capsulatum LexA protein binds specifically to the direct repeat GTTCN(7)GTTC motif. Strikingly, this is also the LexA box of the Alphaproteobacteria, but had not previously been described outside this subclass of the Proteobacteria. In addition, a phylogenetic analysis of the LexA protein clusters together Acidobacterium and the Alphaproteobacteria, moving the latter away from their established phylogenetic position as a subclass of the Proteobacteria, and pointing to a lateral gene transfer of the lexA gene from the phylum Acidobacteria, or an immediate ancestor, to the Alphaproteobacteria. Lastly, in vivo experiments demonstrate that the A. capsulatum recA gene is DNA-damage inducible, despite the fact that a LexA-binding sequence is not present in its promoter region.

MeSH terms

  • Alphaproteobacteria / genetics*
  • Amino Acid Sequence
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / genetics*
  • Bacterial Proteins / isolation & purification
  • Bacterial Proteins / metabolism
  • Binding Sites
  • DNA Damage
  • DNA Repair
  • DNA, Bacterial / genetics*
  • DNA, Bacterial / metabolism
  • DNA-Binding Proteins
  • Electrophoretic Mobility Shift Assay
  • Evolution, Molecular*
  • Gene Transfer, Horizontal*
  • Molecular Sequence Data
  • Phylogeny
  • Promoter Regions, Genetic
  • Protein Binding
  • Rec A Recombinases / analysis
  • SOS Response, Genetics*
  • Sequence Homology, Amino Acid
  • Serine Endopeptidases / chemistry
  • Serine Endopeptidases / genetics*
  • Serine Endopeptidases / isolation & purification
  • Serine Endopeptidases / metabolism


  • Bacterial Proteins
  • DNA, Bacterial
  • DNA-Binding Proteins
  • LexA protein, Bacteria
  • Rec A Recombinases
  • Serine Endopeptidases