Structural studies on the full-length LysR-type regulator TsaR from Comamonas testosteroni T-2 reveal a novel open conformation of the tetrameric LTTR fold
Article first published online: 5 JAN 2010
© 2010 Blackwell Publishing Ltd
Volume 75, Issue 5, pages 1199–1214, March 2010
How to Cite
Monferrer, D., Tralau, T., Kertesz, M. A., Dix, I., Solà, M. and Usón, I. (2010), Structural studies on the full-length LysR-type regulator TsaR from Comamonas testosteroni T-2 reveal a novel open conformation of the tetrameric LTTR fold. Molecular Microbiology, 75: 1199–1214. doi: 10.1111/j.1365-2958.2010.07043.x
- Issue published online: 21 FEB 2010
- Article first published online: 5 JAN 2010
- Accepted 23 December, 2009.
LysR-type transcriptional regulators (LTTRs) constitute the largest family of regulators in prokaryotes. The full-length structures of the LTTR TsaR from Comamonas testosteroni T-2 and its complex with the natural inducer para-toluensulfonate have been characterized by X-ray diffraction. Both ligand-free and complexed forms reveal a dramatically different quaternary structure from that of CbnR from Ralstonia eutropha, or a putative LysR-type regulator from Pseudomonas aeruginosa, the only other determined full-length structures of tetrameric LTTRs. Although all three show a head-to-head tetrameric ring, TsaR displays an open conformation, whereas CbnR and PA01-PR present additional contacts in opposing C-terminal domains that close the ring. Such large differences may be due to a broader structural versatility than previously assumed or either, reflect the intrinsic flexibility of tetrameric LTTRs. On the grounds of the sliding dimer hypothesis of LTTR activation, we propose a structural model in which the closed structures could reflect the conformation of a ligand-free LTTR, whereas inducer binding would bring about local changes to disrupt the interface linking the two compact C-terminal domains. This could lead to a TsaR-like, open structure, where the pairs of recognition helices are closer to each other by more than 10 Å.