RESUMO
DegS (HhoB), a putative serine protease related to DegP/HtrA, regulates the basal and induced activity of the essential Escherichia coli sigma factor sigma (E), which is involved in the cellular response to extracytoplasmic stress. DegS promotes the destabilization of the sigma (E)-specific anti-sigma factor RseA, thereby releasing sigma (E) to direct gene expression. We demonstrate that degS is an essential E. coli gene and show that the essential function of DegS is to provide the cell with sigma (E) activity. We also show that the putative active site of DegS is periplasmic and that DegS requires its N-terminal transmembrane domain for its sigma (E)-related function.
Assuntos
Proteínas de Bactérias/genética , Proteínas de Escherichia coli , Escherichia coli/genética , Fator sigma/metabolismo , Fatores de Transcrição/metabolismo , Proteínas de Bactérias/metabolismo , Sequência de Bases , Membrana Celular/metabolismo , Escherichia coli/efeitos dos fármacos , Escherichia coli/metabolismo , Regulação Bacteriana da Expressão Gênica , Isopropiltiogalactosídeo/farmacologia , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Dados de Sequência Molecular , Periplasma/metabolismo , Fator sigma/genética , Supressão Genética , Fatores de Transcrição/genéticaRESUMO
The activity of the stress-responsive sigma factor, sigma(E), is induced by the extracytoplasmic accumulation of misfolded or unfolded protein. The inner membrane protein RseA is the central regulatory molecule in this signal transduction cascade and acts as a sigma(E)-specific anti-sigma factor. Here we show that sigma(E) activity is primarily determined by the ratio of RseA to sigma(E). RseA is rapidly degraded in response to extracytoplasmic stress, leading to an increase in the free pool of sigma(E) and initiation of the stress response. We present evidence that the putative inner membrane serine protease, DegS, is responsible for this regulated degradation of RseA.
Assuntos
Proteínas de Escherichia coli , Escherichia coli/metabolismo , Regulação Bacteriana da Expressão Gênica , Fator sigma/fisiologia , Fatores de Transcrição/fisiologia , Proteínas de Bactérias/metabolismo , Proteínas de Bactérias/fisiologia , Citoplasma/metabolismo , Genes Reporter , Proteínas de Membrana/biossíntese , Proteínas de Membrana/metabolismo , Mutagênese , Plasmídeos/metabolismo , Testes de Precipitina , Fator sigma/biossíntese , Transdução de Sinais , Temperatura , Fatores de Tempo , Fatores de Transcrição/biossínteseRESUMO
The activity of the alternate sigma-factor sigmaE of Escherichia coli is induced by several stressors that lead to the extracytoplasmic accumulation of misfolded or unfolded protein. The sigmaE regulon contains several genes, including that encoding the periplasmic protease DegP, whose products are thought to be required for maintaining the integrity of the cell envelope because cells lacking sigmaE are sensitive to elevated temperature and hydrophobic agents. Selection of multicopy suppressors of the temperature-sensitive phenotype of cells lacking sigmaE revealed that overexpression of the lipoprotein NlpE restored high temperature growth to these cells. Overexpression of NlpE has been shown previously to induce DegP synthesis by activating the Cpx two-component signal transduction pathway, and suppression of the temperature-sensitive phenotype by NlpE was found to be dependent on the Cpx proteins. In addition, a constitutively active form of the CpxA sensor/kinase also fully suppressed the temperature-sensitive defect of cells lacking sigmaE. DegP was found to be necessary, but not sufficient, for suppression. Activation of the Cpx pathway has also been shown to alleviate the toxicity of several LamB mutant proteins. Together, these results reveal the existence of two partially overlapping regulatory systems involved in the response to extracytoplasmic stress in E. coli.
Assuntos
Proteínas de Escherichia coli , Escherichia coli/genética , Proteínas de Choque Térmico , Resposta ao Choque Térmico/genética , Proteínas Periplásmicas , Proteínas Quinases , Fator sigma/fisiologia , Transdução de Sinais/genética , Fatores de Transcrição/fisiologia , Proteínas da Membrana Bacteriana Externa/genética , Proteínas de Bactérias/fisiologia , Escherichia coli/crescimento & desenvolvimento , Regulação Bacteriana da Expressão Gênica/fisiologia , Genes Bacterianos/fisiologia , Genes Supressores/genética , Lipoproteínas/genética , Fases de Leitura Aberta/genética , Fenótipo , Regulon/fisiologia , Análise de Sequência de DNA , Serina Endopeptidases/genética , Serina Endopeptidases/fisiologia , Fator sigma/genética , Fatores de Transcrição/genéticaRESUMO
The effect of approximation on the postural sway of healthy subjects wearing a weighted belt around their pelvis was measured. Twenty subjects between the ages of 23 and 30 years stood on a polyurethane foam platform that amplified their postural sway and were filmed from a lateral view. All subjects wore markers over their mandibles, hips, and knees and were filmed three times with the weighted belt worn on a randomly selected trial. Frames from a 10-second interval of film from each trial were studied, and the summed displacement at each bony landmark between each frame of film was calculated. A significant decrease in displacement at the mandible (p less than .02) was found when the weighted belt was worn. The decrease in displacement was not significant at the hip or knee. Approximation was shown to decrease the postural sway of healthy subjects. Further study is indicated to investigate the effect of approximation on patient populations.
