title: A supramolecular complex in the environmental stress signalling pathway of Bacillus subtilis.
abstract: SigmaB, an alternative sigma-factor of Bacillus subtilis, mediates the response of the cell to a variety of physical insults. Within the environmental stress signalling pathway RsbU, a protein phosphatase, is stimulated by its interaction with the protein kinase RsbT. In the absence of stress RsbT is expected to be trapped by an alternative binding partner, RsbS. Here, we have demonstrated that RsbS alone cannot act as an alternative partner for RsbT, but instead requires the presence of RsbR to create a high molecular mass RsbR:RsbS complex (approximately 1 MDa) able to capture RsbT. In this complex the phosphorylation state of RsbS, and not that of RsbR, controlled the binding to RsbT, whose kinase activity towards RsbS could be counterbalanced by the activity of RsbX, the phosphatase for RsbS-P. The RsbR:RsbS complex recruited RsbT from a mixture of RsbT and RsbU. The phosphorylated form of RsbR in the complex enhanced the kinase activity of RsbT towards RsbS. This supramolecular complex thus has the functional properties of an alternative partner for RsbT. Electron micrographs of this complex are presented, and the purification of the RsbR:RsbS complex from cellular extracts provides evidence for the existence of such a complex in vivo.
authors.affiliation: Microbiology Unit, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK.
authors.forename: Chien-Cheng
authors.initials: CC
authors.lastname: Chen
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Lewis
authors.forename: Robin
authors.initials: R
authors.lastname: Harris
authors.forename: Michael D
authors.initials: MD
authors.lastname: Yudkin
authors.forename: Olivier
authors.initials: O
authors.lastname: Delumeau
mesh_terms: D001412:Bacillus subtilis / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002846:Chromatography, Affinity; D002850:Chromatography, Gel; D004591:Electrophoresis, Polyacrylamide Gel; D015964:Gene Expression Regulation, Bacterial; D046911:Macromolecular Substances; D008854:Microscopy, Electron; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D010750:Phosphoproteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding; D011494:Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D018085:Regulon; D015398:Signal Transduction
chemical_list: D001426:Bacterial Proteins; D046911:Macromolecular Substances; D010750:Phosphoproteins; C119218:RsbR protein, Bacillus subtilis; D011494:Protein Kinases; C119219:RsbT protein, Bacillus subtilis; D017346:Protein Serine-Threonine Kinases; D010749:Phosphoprotein Phosphatases; D010744:Phosphoric Monoester Hydrolases; C091162:RsbU protein, Bacillus subtilis