PMID:21075890

Citation	Baek, KT, Vegge, CS, Skórko-Glonek, J and Brøndsted, L (2011) Different contributions of HtrA protease and chaperone activities to Campylobacter jejuni stress tolerance and physiology. Appl. Environ. Microbiol. 77:57-66
Abstract	The microaerophilic bacterium Campylobacter jejuni is the most common cause of bacterial food-borne infections in the developed world. Tolerance to environmental stress relies on proteases and chaperones in the cell envelope, such as HtrA and SurA. HtrA displays both chaperone and protease activities, but little is known about how each of these activities contributes to stress tolerance in bacteria. In vitro experiments showed temperature-dependent protease and chaperone activities of C. jejuni HtrA. A C. jejuni mutant lacking only the protease activity of HtrA was used to show that the HtrA chaperone activity is sufficient for growth at high temperature or under oxidative stress, whereas the HtrA protease activity is essential only under conditions close to the growth limit for C. jejuni. However, the protease activity was required to prevent induction of the cytoplasmic heat shock response even under optimal growth conditions. Interestingly, the requirement of HtrA at high temperatures was found to depend on the oxygen level, and our data suggest that HtrA may protect oxidatively damaged proteins. Finally, protease activity stimulates HtrA production and oligomer formation, suggesting that a regulatory role depends on the protease activity of HtrA. Studying a microaerophilic organism encoding only two known periplasmic chaperones (HtrA and SurA) revealed an efficient HtrA chaperone activity and proposed multiple roles of the protease activity, increasing our understanding of HtrA in bacterial physiology.
Links	PubMed PMC3019702 Online version:10.1128/AEM.01603-10
Keywords	Bacterial Proteins/genetics; Bacterial Proteins/metabolism; Campylobacter jejuni/enzymology; Campylobacter jejuni/growth & development; Campylobacter jejuni/physiology; Campylobacter jejuni/radiation effects; Hot Temperature; Molecular Chaperones/genetics; Molecular Chaperones/metabolism; Mutant Proteins/genetics; Mutant Proteins/metabolism; Oxidative Stress; Peptide Hydrolases/genetics; Peptide Hydrolases/metabolism; Stress, Physiological
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Notes

This paper refers to HtrA, UniProtKB Q0P928 (is on strain NCTC11168/ derivatives).

Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
CAMJS:E6RSZ3		GO:0006508: proteolysis	IMP: Inferred from Mutant Phenotype:	P	Fig 1	complete
CAMJE:Q46120		GO:0004252: serine-type endopeptidase activity	ECO:0000315:		F		Fig 1, protease activity of WT compared to serine mutant	complete CACAO 4321
CAMJE:Q46094		GO:0006950: response to stress	ECO:0000315:		P		Fig 3. Effect of temperature and oxidative stress on growth of C. jejuni htrA mutants on solid medium	complete CACAO 4324
CAMJE:Q46094		GO:0006508: proteolysis	ECO:0000315:		P		FIG. 1. Protease activity of HtrA in vitro. (degradation of casein)	complete CACAO 4326

References

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