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The Stress Response and Stress Proteins
Published in John J. Lemasters, Constance Oliver, Cell Biology of Trauma, 2020
Martin E. Feder, Dawn A. Parsell, Susan L. Lindquist
In the cell, these two groups of chaperones apparently work together to promote protein folding in the bacterial cell. DnaK is hypothesized to bind to extensively unfolded proteins; DnaJ then prevents release of these proteins as some folding ensues. GrpE is then thought to promote the transfer of the partially folded protein from DnaJ-DnaK to GroEL, which in combination with GroES, completes the folding reaction. In GroEL, 14 subunits of approximately 60 kD form two stacked seven-member rings surrounding a common central cavity. GroES, also in a seven-member ring, can bind to either end of the GroEL cylinder to form a complex. Martin et al.27 recently proposed a model of how the GroEL-GroES-unfolded protein complex mediates protein folding (Figure 5). According to their model, unfolded protein binds to the inside of the “cage” formed by the two GroEL rings. Binding of GroES to the complex reduces the affinity of GroEL for the unfolded protein, causing their dissociation. The unfolded protein is then free to fold, and the GroEL cage surrounding it shields it from inappropriate interactions with other proteins. If folding is complete, GroEL no longer has affinity for the mature protein, which will exit from the cage. If folding is incomplete, the protein can again be bound by the interior of the GroEL cage, which prompts the dissociation of GroES from the complex. The free GroES is then available to initiate a subsequent cycle of release, folding, and either exit or rebinding of the unfolded protein. Although many details of this model remain to be verified, it provides an intriguing glimpse of how chaperones may work28.
Proteomics Approaches to Uncover the Drug Resistance Mechanisms of Microbial Biofilms
Published in Chaminda Jayampath Seneviratne, Microbial Biofilms, 2017
Chaminda Jayampath Seneviratne, Tanujaa Suriyanarayanan, Lin Qingsong, Juan Antonio Vizcaíno
Neisseria meningitidis is a commensal bacterium that resides in the human nasopharynx but which, under certain conditions, can cause invasive diseases such as meningitis. Comparative proteomics analysis of planktonic and biofilm cultures of N. meningitidis showed that the oxidative defence system–related proteins MntC and SodC were expressed in higher levels in the biofilm mode of growth [44]. MntC and SodC are well-known components of the oxidative defence system. Subsequently, MntC knock-out mutants showed more susceptibility to Paraquat, an agent that induces the production of intracellular reactive oxygen species (ROS). Interestingly, biofilm formation of MntC mutants was completely abrogated. However, this phenotype could be compensated by complementation of mntC in trans. Hence, MntC seems to protect the bacterium against ROS in the biofilm mode of growth, but not in the planktonic mode. In another study, a considerable number of stress response proteins including antioxidants were found to be expressed in high amounts in the Actinomyces naeslundii biofilm, when compared to the planktonic proteome [17]. These proteins included Fe/Mn superoxide dismutase, thioredoxin, general stress protein 14, co-chaperone GrpE HSP10 and HSP70. Superoxide dismutase has been shown to be expressed in higher levels in the biofilm modes compared to the planktonic modes of bacteria such as Listeria monocytogenes and Salmonella enterica [37,60]. The higher expression of alkyl hydroperoxide reductase and catalase–hydroperoxidase II observed in the comparative proteomics study on the planktonic and biofilm mode of Acinetobacter baumannii indicates higher antioxidative capacities in the biofilm mode of growth [15]. Comparative proteomics studies on planktonic versus biofilm modes of bacterial pathogens such as Campylobacter jejuni and H. influenzae have further corroborated that alkylhydroperoxide reductase is an important antioxidant expressed at higher levels in the biofilm mode compared to the planktonic mode [31,39]. Hence, the aforementioned findings provide evidence for the role of antioxidant defence system in the drug resistance of microbial biofilms. The biofilm proteome of another bacterium, Tanerella forsythia, which is associated with periodontal disease, when compared with the planktonic proteome also demonstrated higher expression levels of oxidative stress–related proteins – for example, Dps, AhpC and Hsp20 [77]. T. forsythia biofilm cells were more resistant to oxidative stress than planktonic cells. The proteome of P. aeruginosa also exhibited increased levels of antioxidant proteins in the biofilm mode of growth [53].
Use of genetically modified lactic acid bacteria and bifidobacteria as live delivery vectors for human and animal health
Published in Gut Microbes, 2022
Romina Levit, Naima G. Cortes-Perez, Alejandra de Moreno de Leblanc, Jade Loiseau, Anne Aucouturier, Philippe Langella, Jean Guy LeBlanc, Luis G. Bermúdez-Humarán
Heat-shock proteins are a conserved group of proteins (among which are the groESL and DnaKJ-GrpE chaperone complexes) synthesized in response to different stress stimuli such as heat-shock, low pH, UV irradiation, or salts stress. The SICE system is based on the use of the groESL heat shock protein operon promoter from L. lactis. This episomal system is composed of a vector that carries an expression cassette under the transcriptional control of a stress-inducible promoter.49 In this system, the expression of the protein of interest is induced after administration to the host, since the GM bacterium finds different conditions than those of the culture and suffers different types of stress. Heat stress due to the body temperature of the host higher than the optimal growth temperature of the bacteria; and in the case of oral administration, the acid stress during passage through the stomach added to biliary stress in the duodenum are examples of stresses able to induce expression in this system, and allow the in situ production of the molecule of interest. The main advantage of this system is that it does not require the presence of regulatory genes or the induction in cultures before use.50,51
Functional analysis and cryo-electron microscopy of Campylobacter jejuni serine protease HtrA
Published in Gut Microbes, 2020
Urszula Zarzecka, Alessandro Grinzato, Eaazhisai Kandiah, Dominik Cysewski, Paola Berto, Joanna Skorko-Glonek, Giuseppe Zanotti, Steffen Backert
All bacteria have effective stress responses to limit protein damage under harsh environmental conditions. In addition to the common cytoplasmic stress response proteins (DnaK, GroES/EL, GrpE, DnaJ, ClpB, etc.),19,20 the HtrA (high-temperature requirement A) protein plays an important protective function in the cellular envelope. This protein exhibits both protease and chaperone activities and is found in almost all bacteria.21 The best-characterized member of this protein family is HtrA from Escherichia coli (HtrAEc, also known as DegP).22,23 As a protein quality control factor, DegP recognizes and degrades proteins that are not properly folded. In particular, DegP preferentially digests unfolded polypeptides with exposed hydrophobic residues and it mainly hydrolyzes peptide bonds after hydrophobic amino acid residues.24 A characteristic feature of the HtrA family of proteins is the presence of a chymotrypsin-type protease domain as well as one or two C-terminal PDZ domains (Postsynaptic density protein 95, Drosophila disc large tumor suppressor and Zonula occludens-1 protein domain).25 PDZ domains are typically involved in substrate binding, regulation of the proteolytic activity and inter-subunitinteractions.26
Chaperonomics in leptospirosis
Published in Expert Review of Proteomics, 2018
Arada Vinaiphat, Visith Thongboonkerd
DnaK consists of two domains, including an ATPase domain and a protein-binding domain [2]. DnaK regulatory process depends on transient interaction of its ATPase and substrate-binding domains. The interaction between substrate-binding domain and short segments of polypeptides is facilitated by another co-chaperone known as DnaJ and a nucleotide-exchange factor (NEF; GrpE homolog in prokaryotes). DnaJ binds to non-native proteins during cellular stress to prevent aggregation or binds to newly synthesized proteins to prevent premature folding before targeting them to DnaK. Upon delivering and forming a ternary complex with DnaK, DnaJ activates hydrolysis reaction of the bound ATP via its J-domain, resulting in either reversion of aggregation or progression of denaturation of the aggregates to avoid toxic interactions. Final release of the substrate is then catalyzed by GrpE [15,17].