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Figure 5
(a) Structural superposition of the PpsR Q-PAS1 dimers of PpsRΔHTH (protomers A and B, blue; protomers C and D, green), PpsRN-Q-PAS1 (yellow) as well as the recently published AppA–(PpsR)2 complex structure (black; PDB entry 4hh3 ; Winkler et al., 2013BB71). The PAS1 dimers and their corresponding N-caps are rigid dimer modules (bright colours) that exhibit an identical conformation in all structures, whereas the corresponding N-terminal helical regions of the Q-­linkers (pale colours) show different relative orientations. Even in the AppA–(PpsR)2 complex structure, where the asymmetric binding of AppA to PpsR induces significant structural changes in the conformation of the Q-linker (Winkler et al., 2013BB71), the conformations of the PAS1 and N-­domain dimers, including their N-caps, are unchanged. (b) The structure of the S-helix PAS domain dimer of VicK (PDB entry 4i5s ; Wang et al., 2013BB68) shows a very similar conformation to that observed for the Q-linkers and PAS1 domains of PpsR. For reasons of clarity, the N-terminal HAMP and the C-terminal S-­helix and DHp domains are not shown. (c) The structure of the S-helix PAS domain dimer of HTR-like protein (PDB entry 3bwl ; protomers A and B) also exhibits a comparable conformation to that observed for PpsR and VicK. The PAS domains of the HTR-like protein have an 1H-indole-3-carbaldehyde ligand that is shown as stick model.

Journal logoBIOLOGICAL
ISSN: 1399-0047
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