Overall Structure

DesT consists of two parallel subunits that form a homodimer, with each subunit made of nine α-helices :

- the DNA-binding domain is created by the three N-terminal α-helices

- the six C-terminal α-helices create the ligand binding domain.

Diagram1: Blue represents the surface of the ligand-binding domain while orange represents the α helices that form this domain.

In the ligand binding domain, the helices α4, α5, α7, α8 and α9 are arranged in an antiparallel bundle with helix α6 crossing the 'top' of the bundle diagonally, as seen in diagram 1. This forms a platform for the DNA-binding domain. Hydrophobic interactions between helices α8 and α9 create a central four-helix bundle within the dimer.

Diagram 2: an overlay of DesT DNA-binding domains. Cyan represents the relaxed state. Slate-blue represents the tense state. [Diagram taken from here.]

Diagram 2 shows the DNA-binding domain of DesT in both tense and relaxed states. Helices α4 and α6 (not shown in diagram 2) are shared between both the DNA and ligand-binding domain. Their conformation in response to the shape of the ligand results in a conformational change in the α helices involved in the DNA binding domain, controlling their interactions with the DNA. DesT has a defined structural pathway to relay  information over 40Å, from the ligand-binding domain to the DNA-binding domain.

DesT-oleoyl-CoA-DNA complex corresponds to the relaxed state.

DesT-palmitoyl-CoA complex represents the tense state.

<previous page                                                                                                                                                                 next page>