Regulation of the heat shock response in Escherichia coli: history and perspectives.

The heat shock response mediated by transcription factor σ is a major stress response to cope with heat and other stresses in Escherichia coli. Although much attention has been paid to the role of highly conserved heat shock proteins such as chaperones and proteases in sustaining cellular protein homeostasis under stress, relatively little is known about the dynamic nature of underlying regulatory mechanisms. When cells are suddenly exposed to high temperature, synthesis of σ is rapidly induced by activated translation of rpoH mRNA, which encodes σ, through disruption of mRNA secondary structure.

Heat shock transcription factor σ defective in membrane transport can be suppressed by transposon insertion into genes encoding a restriction enzyme subunit or a putative autotransporter in Escherichia coli.

Heat shock transcription factor σ of Escherichia coli plays a major role in protein homeostasis and requires membrane localization for regulation. We here report that a strongly deregulated I54N-σ mutant defective in association with the membrane can be phenotypically suppressed by Tn5 insertion into the mcrC or ydbA2 gene, encoding a restriction enzyme subunit or part of a putative autotransporter, respectively. The suppression is specific for mutant I54N-σ and reduces its activity but not its abundance or stability.

A Novel SRP Recognition Sequence in the Homeostatic Control Region of Heat Shock Transcription Factor σ32.

Heat shock response (HSR) generally plays a major role in sustaining protein homeostasis. In Escherichia coli, the activity and amount of the dedicated transcription factor σ(32) transiently increase upon heat shock. The initial induction is followed by chaperone-mediated negative feedback to inactivate and degrade σ(32).

Heat shock transcription factor σ32 co-opts the signal recognition particle to regulate protein homeostasis in E. coli.

All cells must adapt to rapidly changing conditions. The heat shock response (HSR) is an intracellular signaling pathway that maintains proteostasis (protein folding homeostasis), a process critical for survival in all organisms exposed to heat stress or other conditions that alter the folding of the proteome. Yet despite decades of study, the circuitry described for responding to altered protein status in the best-studied bacterium, E.

Convergence of molecular, modeling, and systems approaches for an understanding of the Escherichia coli heat shock response.

The heat shock response (HSR) is a homeostatic response that maintains the proper protein-folding environment in the cell. This response is universal, and many of its components are well conserved from bacteria to humans. In this review, we focus on the regulation of one of the most well-characterized HSRs, that of Escherichia coli.

Analysis of sigma32 mutants defective in chaperone-mediated feedback control reveals unexpected complexity of the heat shock response.

Protein quality control is accomplished by inducing chaperones and proteases in response to an altered cellular folding state. In Escherichia coli, expression of chaperones and proteases is positively regulated by sigma32. Chaperone-mediated negative feedback control of sigma32 activity allows this transcription factor to sense the cellular folding state.

Conserved region 2.1 of Escherichia coli heat shock transcription factor sigma32 is required for modulating both metabolic stability and transcriptional activity.

Escherichia coli heat shock transcription factor sigma32 is rapidly degraded in vivo, with a half-life of about 1 min. A set of proteins that includes the DnaK chaperone team (DnaK, DnaJ, GrpE) and ATP-dependent proteases (FtsH, HslUV, etc.) are involved in degradation of sigma32.

Proteome analysis of plant-induced proteins of Agrobacterium tumefaciens.

Abstract A proteome study of Agrobacterium tumefaciens exposed to plant roots demonstrated the existence of a plant-dependent stimulon. This stimulon was induced by exposure to cut roots and consists of at least 30 soluble proteins (pI 4-7), including several proteins whose involvement in agrobacteria-host interactions has not been previously reported. Exposure of the bacteria to tomato roots also resulted in modification of the proteins: Ribosomal Protein L19, GroEL, AttM, and ChvE, indicating the significance of protein modifications in the interactions of agrobacteria with plants.

The increment of anti-ORP150 autoantibody in initial stages of atheroma in high-fat diet fed mice.

Expression of 150 kda oxygen-regulated protein, ORP150, was examined in the atheromatous lesions on aortic valves in high-fat diet fed mice. Immunohistochemical staining revealed that ORP150 was expressed on the surface of plaque and was co-localized with phagocytes bearing Mac-3, a mouse macrophage differentiation antigen. These findings suggest that ORP150 is involved in the development of the atheromatous plaque.

Heat shock proteome of Agrobacterium tumefaciens: evidence for new control systems.

The regulation of Agrobacterium tumefaciens heat shock genes involves a transcriptional activator (RpoH) and repressor elements (HrcA-CIRCE). Using proteome analysis and mutants in these control elements, we show that the heat shock induction of 32 (out of 56) heat shock proteins is independent of RpoH and HrcA. These results indicate the existence of additional regulatory factors in the A.