The N-terminal region of HtrA heat shock protease from Escherichia coli is essential for stabilization of HtrA primary structure and maintaining of its oligomeric structure

The proteolytic activity of the HtrA (DegP) protein from Escherichia coli at low temperatures

“…Within the LA loop there is a disulfide bridge (C57-C69), which is introduced by DsbA (Skorko-Glonek et al, 2006). The presence of this S-S bond was shown to contribute to the maintenance of protein stability (Skorko-Glonek et al, 2003). HtrA deprived of the S-S bond (either by mutation or by reducing agents) was prone to autocleavage even at 4 u C (our unpublished observation).…”

“…The anti-AP polyclonal antibodies were from Chemikon. The anti-HtrA rabbit polyclonal antibodies were obtained in our laboratory by affinity chromatography using an immobilized HtrA protein as described by Skorko-Glonek et al (2003). Immobilon-P, 0.45 mm for immunoblotting, was obtained from Millipore.…”

“…It is a periplasmic serine protease indispensable for the survival of E. coli at elevated temperatures and under certain conditions of oxidative stress (Lipinska et al, 1989;Skorko-Glonek et al, 1999). The expression of the htrA gene is upregulated in response to various stress conditions, including heat shock, oxidative stress and the presence of reducing agents (Skorko-Glonek et al, 2003). This protein plays a very important role in the extracytoplasmic protein quality control system, as it is a major periplasmic protease responsible for degrading damaged or abnormal polypeptides within the cellular envelope .…”

“…The LA loop comes from the opposing monomer (Krojer et al, 2002). Within the LA loop there is a disulfide bridge, important for maintaining protein stability (Skorko-Glonek et al, 2003). In the recent work of Krojer et al (2008) it was shown that during the activation process the HtrA hexamer disassembles to trimers, which subsequently form 12-mers or 24-mers.…”

The HtrA Protease from Streptococcus pneumoniae Digests Both Denatured Proteins and the Competence-stimulating Peptide

“…Such autodigestion has been noted for other proteases in the HtrA family, including DegP (38). Although we have not directly compared the stability of our protease with that of DegP, self-cleavage may be enhanced in the case of pneumococcal HtrA due to the lack of cysteine residues and a disulfide bridge that has been shown to be important for stabilizing DegP against autodigestion (38).…”