title: Dual molecular signals mediate the bacterial response to outer-membrane stress.
abstract: In Gram-negative bacteria, outer-membrane integrity is essential for survival and is monitored by the σ(E) stress-response system, which initiates damage-repair pathways. One activating signal is unassembled outer-membrane proteins. Using biochemical and genetic experiments in Escherichia coli, we found that off-pathway intermediates in lipopolysaccharide transport and assembly provided an additional required signal. These distinct signals, arising from disruptions in the transport and assembly of the major outer-membrane components, jointly determined the rate of proteolytic destruction of a negative regulator of the σ(E) transcription factor, thereby modulating the expression of stress-response genes. This dual-signal system permits a rapid response to dysfunction in outer-membrane biogenesis, while buffering responses to transient fluctuations in individual components, and may represent a broad strategy for bacteria to monitor their interface with the environment.
authors.affiliation: Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
authors.forename: Santiago
authors.initials: S
authors.lastname: Lima
authors.forename: Monica S
authors.initials: MS
authors.lastname: Guo
authors.forename: Rachna
authors.initials: R
authors.lastname: Chaba
authors.forename: Carol A
authors.initials: CA
authors.lastname: Gross
authors.forename: Robert T
authors.initials: RT
authors.lastname: Sauer
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism*; D001692:Biological Transport; D002352:Carrier Proteins / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000378:metabolism; D008050:Lipid A / Q000378:metabolism; D008070:Lipopolysaccharides / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D059748:Proteolysis; D012808:Sigma Factor / Q000378:metabolism; D015398:Signal Transduction; D013312:Stress, Physiological; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D001425:Bacterial Outer Membrane Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D008050:Lipid A; D008070:Lipopolysaccharides; C532155:LptA protein, E coli; D008565:Membrane Proteins; C433802:RseA protein, E coli; C494790:RseB protein, E coli; D012808:Sigma Factor; D014157:Transcription Factors; C063202:sporulation-specific sigma factors