Molecule of the Month
September 2006
A New Function for an Old Fold

The enzymes of metabolic pathways have by and large been conserved in all kingdoms of life. In contrast, the mechanisms of pathway control are diverse. This is most obvious at the level of gene expression. The transcription of the dihydroxyacetone kinase genes in bacteria is one example of such diversity. The transcription factor DhaR from Lactococcus lactis belong to the TetR family. All 300 known members from this family are repressors of transcription that are inactivated by low molecular weight organic compounds.
DhaR, in contrast, functions as an activator of transcription that is activated by the dihydroxyacetone binding protein DhaQ. Binding of DhaR to the operator DNA (blue) protects an inverted repeat (red) and renders two GC base pairs hypersensitive to DNaseI cleavage. Shown are DhaR and operator DNA. The helix-turn-helix motif of DhaR is coloured blue and red.

This work was carried out in the group of Prof. Bernhard Erni.


  • S. Christen, A. Srinivas, P. Bahler, A. Zeller, D. Pridmore, C. Bieniossek, U. Baumann, B. Erni;
    "Regulation of the Dha operon of Lactococcus lactis: a deviation from the rule followed by the TetR family of transcription regulators"
    J. Biol. Chem., 281, 23129-23137, (2006); doi:10.1074/jbc.M603486200.