Conversion of a regulatory into a degradative protease.

The PDZ protease DegS senses mislocalized outer membrane proteins and initiates the sigmaE pathway in the bacterial periplasm. This unfolded protein response pathway is activated by processing of the anti-sigma factor RseA by DegS and other proteases acting downstream of DegS. DegS mediates the rate-limiting step of sigma E induction and its activity must be highly specific and tightly regulated.

Structure, function and regulation of the conserved serine proteases DegP and DegS of Escherichia coli.

Two members of the widely conserved HtrA family of serine proteases, DegP and DegS, are key players in extracytoplasmic protein quality control. The underlying mechanisms of their main functions in stress sensing, regulation and protection during the unfolded protein response are discussed.

Peptidic small molecule activators of the stress sensor DegS.

Bacterial DegS is a regulatory protease that acts as a molecular stress sensor and initiates a periplasmic stress response pathway. Upon binding of misfolded proteins to its PDZ domain, the protease domain of DegS is allosterically activated, thereby initiating a signal cascade that results in the elevated expression of protein quality control factors. Although the structural basis of this activation mode has been elucidated previously, it is not yet fully understood if binding to the PDZ domain is sufficient for protease domain activation or if secondary interactions with the protease domain are required.

Transcriptional control of the succinate dehydrogenase operon sdhCAB of Corynebacterium glutamicum by the cAMP-dependent regulator GlxR and the LuxR-type regulator RamA.

In experiments performed to identify transcriptional regulators of the tricarboxylic acid cycle of Corynebacterium glutamicum, the cAMP-dependent regulator GlxR and the regulators of acetate metabolism RamA and RamB were enriched by DNA affinity chromatography with the promoter region of the sdhCAB operon encoding succinate dehydrogenase. The binding of purified GlxR, RamA and RamB was verified by electrophoretic mobility shift assays and the regulatory effects of these proteins on sdhCAB gene expression were tested by promoter activity assays and SDH activity measurements. Evidence was obtained that GlxR functions as a repressor and RamA as an activator of sdhCAB expression, whereas RamB had no obvious influence under the conditions tested.

Co-ordinated regulation of gluconate catabolism and glucose uptake in Corynebacterium glutamicum by two functionally equivalent transcriptional regulators, GntR1 and GntR2.

Corynebacterium glutamicum is a Gram-positive soil bacterium that prefers the simultaneous catabolism of different carbon sources rather than their sequential utilization. This type of metabolism requires an adaptation of the utilization rates to the overall metabolic capacity. Here we show how two functionally redundant GntR-type transcriptional regulators, designated GntR1 and GntR2, co-ordinately regulate gluconate catabolism and glucose uptake.

High-resolution structure of the histidine-containing phosphocarrier protein (HPr) from Staphylococcus aureus and characterization of its interaction with the bifunctional HPr kinase/phosphorylase.

A high-resolution structure of the histidine-containing phosphocarrier protein (HPr) from Staphylococcus aureus was obtained by heteronuclear multidimensional nuclear magnetic resonance (NMR) spectroscopy on the basis of 1,766 structural restraints. Twenty-three hydrogen bonds in HPr could be directly detected by polarization transfer from the amide nitrogen to the carbonyl carbon involved in the hydrogen bond. Differential line broadening was used to characterize the interaction of HPr with the HPr kinase/phosphorylase (HPrK/P) of Staphylococcus xylosus, which is responsible for phosphorylation-dephosphorylation of the hydroxyl group of the regulatory serine residue at position 46.

Pyrophosphate-producing protein dephosphorylation by HPr kinase/phosphorylase: a relic of early life?

In most Gram-positive bacteria, serine-46-phosphorylated HPr (P-Ser-HPr) controls the expression of numerous catabolic genes ( approximately 10% of their genome) by acting as catabolite corepressor. HPr kinase/phosphorylase (HprK/P), the bifunctional sensor enzyme for catabolite repression, phosphorylates HPr, a phosphocarrier protein of the sugar-transporting phosphoenolpyruvate/glycose phosphotransferase system, in the presence of ATP and fructose-1,6-bisphosphate but dephosphorylates P-Ser-HPr when phosphate prevails over ATP and fructose-1,6-bisphosphate. We demonstrate here that P-Ser-HPr dephosphorylation leads to the formation of HPr and pyrophosphate.

Structure of the full-length HPr kinase/phosphatase from Staphylococcus xylosus at 1.95 A resolution: Mimicking the product/substrate of the phospho transfer reactions.

The histidine containing phospho carrier protein (HPr) kinase/phosphatase is involved in carbon catabolite repression, mainly in Gram-positive bacteria. It is a bifunctional enzyme that phosphorylates Ser-46-HPr in an ATP-dependent reaction and dephosphorylates P-Ser-46-HPr. X-ray analysis of the full-length crystalline enzyme from Staphylococcus xylosus at a resolution of 1.