Chapter 1: Variation in form and function the helix-turn-helix regulators of the GntR superfamily.

One of the most abundant and widely distributed groups of Helix-turn-helix (HTH) transcription factors is the metabolite-responsive GntR family of regulators (>8500 members in the Pfam database; Jan 2009). These proteins contain a DNA-binding HTH domain at the N terminus of the protein and an effector-binding and/or oligomerisation domain at the C terminus, where upon on binding an effector molecule, a conformational change occurs in the protein which influences the DNA-binding properties of the regulator resulting in repression or activation of transcription. This review summarises what we know about the distribution, structure, function and classification of these regulators and suggests that they may have a future role in biotechnology.