Thus, the PASBvg domain might sense intracellular molecule(s) whose abundance reflect(s) the metabolic state of the bacterium, and changes to the concentration of these components might affect signaling. Such a scenario would be compatible with the ‘rheostat’ behavior attributed to BvgS [3]. In any case, the effects of cavity mutations on BvgS activity this website lend strong support to our model that the conformation of the PAS core –intrinsically or by virtue of ligand binding- is critical for

signaling. Conclusions Although substantial information has been gathered about how the cytoplasmic domains of BvgS work, the function of its PAS domain has remained unknown. In this work, we performed its characterization, which represents new information that contributes to our understanding of VFT-containing sensor-kinases. We showed that the recombinant PAS domain of the sensor-kinase BvgS dimerises, and that the N- and C-terminal α-helical regions that flank the PAS core are critical for dimer stabilization. We identified specific amino acid residues in the PAS domain that are essential for BvgS activity, located in the PAS core and NVP-BSK805 nmr at the junctions between it and its flanking α helices. We thus propose a mechanical role for the PAS domain in BvgS, which is to maintain

the conformational tension imposed by the periplasmic moiety of BvgS. The degree of tension in the protein determines the activity of the kinase, and modulation corresponds to an increased tension. Our model thus explains for the first time the phenotypes of a number of BvgS variants that harbor mild substitutions in the PAS domain and are unable to respond to negative modulation. Acknowledgements We thank Eve Willery for the Erismodegib nmr construction of BPSMΔbvgA. E. D. was supported by a pre-doctoral grant from during the French Ministry for Research and then by a grant from the Fonds de la Recherche Médicale (FRM). This work was supported by funds from INSERM, CNRS, and University Lille-Nord de France. Electronic supplementary

material Additional file 1: Table S1: Oligonucleotides used in this study. (PDF 48 KB) References 1. Gao R, Stock AM: Biological insights from structures of two-component proteins. Annu Rev Microbiol 2009, 63:133–154.PubMedCrossRef 2. Casino P, Rubio V, Marina A: The mechanism of signal transduction by two-component systems. Curr Opin Struct Biol 2010, 20:763–771.PubMedCrossRef 3. Cotter PA, Jones AM: Phosphorelay control of virulence gene expression in Bordetella. Trends Microbiol 2003, 11:367–373.PubMedCrossRef 4. Uhl MA, Miller JF: Integration of multiple domains in a two-component sensor protein: the Bordetella pertussis BvgAS phosphorelay. EMBO J 1996, 15:1028–1036.PubMed 5. Jacob-Dubuisson F, Wintjens R, Herrou J, Dupré E, Antone R: BvgS of pathogenic Bordetellae: a paradigm for sensor kinase with Venus Flytrap perception domains. In Two-component system in bacteria. Edited by: Gros R, Beier D.