Initial characterization of the <i>Streptococcus gordonii htpX</i> gene

Vickerman, M. Margaret; Mather, Niklas; Minick, P. E.; Edwards, Chris

doi:10.1046/j.0902-0055.2001.00000.x

Cited by 13 publications

(11 citation statements)

References 39 publications

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“…Subsequently, it was also shown that the htpX gene in Xylella fastidiosa was induced by an increase in temperature (16), whereas the Streptococcus gordonii htpX was not heat-inducible (17). Disruption of S. gordonii htpX caused changes in several properties of the cell surface, although the relationship of these changes with any protease activity of HtpX was unclear (17).…”

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confidence: 99%

Proteolytic Activity of HtpX, a Membrane-bound and Stress-controlled Protease from Escherichia coli

Sakoh

Ito

Akiyama

2005

Journal of Biological Chemistry

100

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Escherichia coli HtpX is a putative membrane-bound zinc metalloprotease that has been suggested to participate in the proteolytic quality control of membrane proteins in conjunction with FtsH, a membrane-bound and ATP-dependent protease. Here, we biochemically characterized HtpX and confirmed its proteolytic activities against membrane and soluble proteins. HtpX underwent selfdegradation upon cell disruption or membrane solubilization. Consequently, we purified HtpX under denaturing conditions and then refolded it in the presence of a zinc chelator. When supplemented with Zn 2؉ , the purified enzyme exhibited self-cleavage activity. In the presence of zinc, it also degraded casein and cleaved a solubilized membrane protein, SecY. We verified its ability to cleave SecY in vivo by overproducing both HtpX and SecY. These results showed that HtpX is a zinc-dependent endoprotease member of the membrane-localized proteolytic system in E. coli.It is vital for cells that membranes and membrane proteins retain their integrity. Malfolded and misassembled membrane proteins, produced under stressful conditions and in non-physiological situations, should receive proteolytic quality control. In Escherichia coli, FtsH, a membrane-bound and ATP-dependent zinc metalloprotease, is known to play a central role in the degradation of unstable membrane proteins (1, 2). Thus, it degrades SecY, a subunit of protein translocase (3), and Fo subunit a of proton ATPase (4) when they have failed to assemble. It also degrades YccA, the function of which is unknown (5), and some unstable cytosolic proteins (1, 2). A characteristic feature of FtsH is that it processively degrades membrane-protein substrates by recognizing their ends when they protrude sufficiently into the cytosol (6, 7). This degradation appears to be accompanied by dislocation of the substrate from the membrane, a process presumably mediated by the ATPase function of .In E. coli, only a few other membrane-integrated proteases are known: DegS and RseP (YaeL), which introduce regulated cleavage into a membrane-bound substrate (11-13), and Lep, which cleaves off a signal peptide of secretory precursor proteins (14). HtpX was first described by Kornitzer et al. (15) as a heat-inducible protein from E. coli with sequence features of a membrane protein and a metalloprotease. They showed that its expression, in a form truncated at the C-terminal, enhanced degradation of cellular proteins in puromycin-treated cells (15). Subsequently, it was also shown that the htpX gene in Xylella fastidiosa was induced by an increase in temperature (16), whereas the Streptococcus gordonii htpX was not heat-inducible (17). Disruption of S. gordonii htpX caused changes in several properties of the cell surface, although the relationship of these changes with any protease activity of HtpX was unclear (17).We rediscovered HtpX during the course of study of cellular responses to "membrane protein stress." Our results showed that ftsH disruption led to the induction of the Cpx stress response, which wa...

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confidence: 99%

Proteolytic Activity of HtpX, a Membrane-bound and Stress-controlled Protease from Escherichia coli

Sakoh

Ito

Akiyama

2005

Journal of Biological Chemistry

100

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“…Notably, the gene encoding pyrolysin, a membrane-associated protease with an endo-acting and subtilisin-like catalytic domain (41), was strongly repressed, while a subtilisin-like protease (18) was strongly induced. Five peptidase-encoding genes were induced, including the gene encoding HtpX, which has been implicated elsewhere in surface protein expression related to changes in adhesiveness, cellular morphology, and levels of surface-active antigens (38).…”

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confidence: 99%

Heat Shock Response by the Hyperthermophilic Archaeon Pyrococcus furiosus

Shockley

Ward

Chhabra

et al. 2003

Appl Environ Microbiol

107

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Collective transcriptional analysis of heat shock response in the hyperthermophilic archaeon Pyrococcus furiosus was examined by using a targeted cDNA microarray in conjunction with Northern analyses. Differential gene expression suggests that P. furiosus relies on a cooperative strategy of rescue (thermosome [Hsp60], small heat shock protein [Hsp20], and two VAT-related chaperones), proteolysis (proteasome), and stabilization (compatible solute formation) to cope with polypeptide processing during thermal stress.Information gleaned from genome sequence data indicates that heat shock response in hyperthermophilic archaea has several distinguishing features. For example, hyperthermophilic archaea lack Hsp70 (DnaK), Hsp40 (DnaJ), and GrpE, all of which are centrally important in the heat shock response of most known microorganisms (26). Also, the major chaperonin found thus far in thermophilic archaea, an Hsp60 homolog referred to as the thermosome, is more closely related to chaperonins associated with the eukaryotic cytosol (TriCC/CCT complex) than to the bacterial GroEL/ES system (19, 32). Energy-dependent proteolysis plays a major role during heat shock in bacteria in which genes encoding ATP-dependent proteases, such as lon, clp, and hfl, are linked to heat shock promoters (13). However, based on available genome sequence data, hyperthermophilic archaea lack the Clp and HflB (FtsH) family of proteins and have a different version of the Lon protease (43). Hyperthermophilic archaea, which typically have proteasomes, lack the eukaryotic ubiquitination pathway for selective protein degradation by the proteasome and, therefore, seem to modulate proteolysis at the protease level. Another interesting feature of hyperthermophilic archaeal heat shock response is the induced formation of unique compatible solutes that have been proposed to stabilize intracellular proteins against thermal denaturation (33). Whether compatible solutes reduce the need for protein turnover mechanisms is not known.The relative contributions to the collective response of chaperones, chaperonins, proteases, and compatible solutes during heat shock in hyperthermophilic archaea have yet to be examined. Here, the heat shock response of the hyperthermophilic archaeon Pyrococcus furiosus (9) was investigated by using Northern analyses in conjunction with a targeted cDNA microarray, based on genes encoding the thermosome, molecular chaperones, proteases, glycoside hydrolases, and other relevant cellular functions expected to be affected during thermal stress.Experimental approach and data analysis. Relevant open reading frames (ORFs) were located from the P. furiosus genome at NCBI (http://www.ncbi.nlm.nih.gov/cgi-bin/Entrez /framik?dbϭgenome&gi ϭ 228) and BLAST searches of prokaryotic genomes found at The Institute for Genomic Research (www.TIGR.org). SCANPROSITE (http://expasy.cbr .nrc.ca/tools/scnpsit1.html) and PFAM HMM (Ͼhttp://pfam .wustl.edu/hmmsearch.shtml) search tools were used to verify the presence of putative catalytic domains. ORF fra...

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“…These heat shock proteins respond to changes in temperature, exposure to UV irradiation, bacteriophage infection, and the presence of accumulated misfolded proteins (60)(61)(62)(63)(64)(65). The proposed role of M48 metalloproteases is in the degradation of misfolded intracellular proteins (21,28,31,62).…”

Section: Discussionmentioning

confidence: 99%

“…Orthologs of HtpX are present in nearly all bacteria. Mutational inactivation of HtpX causes increased thermal sensitivity, growth retardation, abnormal protein translocation, accumulation of misfolded products, and altered surface adhesiveness, cellular morphology, and surface antigen expression (28)(29)(30)(31). This suggests that HtpX plays a central role in maintaining the various functions of the outer membrane.…”

mentioning

confidence: 99%

Precipitation of Iron on the Surface of Leptospira interrogans Is Associated with Mutation of the Stress Response Metalloprotease HtpX

Henry

Khoo

et al. 2013

Appl Environ Microbiol

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e High concentrations of free metal ions in the environment can be detrimental to bacterial survival. However, bacteria utilize strategies, including the activation of stress response pathways and immobilizing chemical elements on their surface, to limit this toxicity. In this study, we characterized LA4131, the HtpX-like M48 metalloprotease from Leptospira interrogans, with a putative role in bacterial stress response and membrane homeostasis. Growth of the la4131 transposon mutant strain (L522) in 360 M FeSO 4 (10-fold the normal in vitro concentration) resulted in the production of an amorphous iron precipitate. Atomic force microscopy and transmission electron microscopy analysis of the strain demonstrated that precipitate production was associated with the generation and release of outer membrane vesicles (OMVs) from the leptospiral surface. Transcriptional studies indicated that inactivation of la4131 resulted in altered expression of a subset of metal toxicity and stress response genes. Combining these findings, this report describes OMV production in response to environmental stressors and associates OMV production with the in vitro activity of an HtpX-like metalloprotease.

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Initial characterization of the Streptococcus gordonii htpX gene

Cited by 13 publications

References 39 publications

Proteolytic Activity of HtpX, a Membrane-bound and Stress-controlled Protease from Escherichia coli

Proteolytic Activity of HtpX, a Membrane-bound and Stress-controlled Protease from Escherichia coli

Heat Shock Response by the Hyperthermophilic Archaeon Pyrococcus furiosus

Precipitation of Iron on the Surface of Leptospira interrogans Is Associated with Mutation of the Stress Response Metalloprotease HtpX

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