title: Stoichiometry and perturbation studies of the LiaFSR system of Bacillus subtilis.
abstract: The response regulator/histidine kinase pair LiaRS of Bacillus subtilis, together with its membrane-bound inhibitor protein LiaF, constitutes an envelope stress-sensing module that is conserved in Firmicutes bacteria. LiaR positively autoregulates the expression of the liaIH-liaGFSR operon from a strictly LiaR-dependent promoter (P(liaI) ). A comprehensive perturbation analysis revealed that the functionality of the LiaFSR system is very susceptible to alterations of its protein composition and amounts. A genetic analysis indicates a LiaF:LiaS:LiaR ratio of 18:4:1. An excess of LiaS over LiaR was subsequently verified by quantitative Western analysis. This stoichiometry, which is crucial to maintain a functional Lia system, differs from any other two-component system studied to date, in which the response regulator is present in excess over the histidine kinase. Moreover, we demonstrate that LiaS is a bifunctional histidine kinase that acts as a phosphatase on LiaR in the absence of a suitable stimulus. An increased amount of LiaR - both in the presence and in the absence of LiaS - leads to a strong induction of P(liaI)  activity due to phosphorylation of the response regulator by acetyl phosphate. Our data demonstrate that LiaRS, in contrast to other two-component systems, is non-robust with regard to perturbations of its stoichiometry.
authors.affiliation: Department of Biology I, Ludwig-Maximilians-University Munich, Munich, Germany.
authors.forename: Karen
authors.initials: K
authors.lastname: Schrecke
authors.forename: Sina
authors.initials: S
authors.lastname: Jordan
authors.forename: Thorsten
authors.initials: T
authors.lastname: Mascher
mesh_terms: D001412:Bacillus subtilis / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D000071677:Histidine Kinase; D009876:Operon; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D011494:Protein Kinases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D011494:Protein Kinases; D000071677:Histidine Kinase