DNA binding mechanism of an unusual bacterial transcription regulator

Transcription factors are vital molecules that control gene expression in response to changes in the cell¿s environment. GabR is a chimeric transcription factor from Bacillus subtilis belonging to the GntR family and controls genes involved in the metabolism of ¿-aminobutyric acid (GABA). The recently published crystal structure of GabR reveals a head-to-tail domain swap dimer whereby the C-terminal aminotransferase I-like domains form the dimeric core with the N-terminal winged helix-turn-helix DNA binding domains located at opposing sides of the core. This unusual structure has raised questions about the structural changes required for DNA binding and the switch from transcriptional repression to activation upon binding of the effector molecule GABA.