Co-expression of chaperonin GroEL/GroES enhances in vivo folding of yeast mitochondrial aconitase and alters the growth characteristics of Escherichia coli

Cobalt-induced stress reveals a prominent role of CzcC on the proteomic profile of Gluconacetobacter diazotrophicus PAL5

AIMS

Heavy metal accumulation in agricultural areas is a global environmental problem that affects microorganisms and plants, with serious implications for human health. This study aimed to investigate the molecular responses of the plant growth-promoting bacterium Gluconacetobacter diazotrophicus PAL5 to cobalt stress.

METHODS AND RESULTS

We evaluated bacterial growth and cell viability under cobalt stress and performed comparative proteomic and reverse genetics analyses. Cobalt significantly inhibited bacterial growth but did not cause cell death. Proteomic analysis in the presence of 2.5 mmol l-1 CoCl2, which caused ∼50% growth inhibition, revealed the induction of pathways related to iron uptake, carbohydrate metabolism, amino acid metabolism, quality control, and efflux. Knockout mutants for genes involved in these pathways (∆tbdR, ∆zwf, ∆pdhB, ∆argH, and ∆czcC) confirmed the essential role of the CzcC efflux system in cobalt tolerance.

CONCLUSIONS

Cobalt stress triggers molecular responses in G. diazotrophicus PAL5, with efflux systems playing a crucial role in stress tolerance.

Chaperonin: Co-chaperonin Interactions

Co-chaperonins function together with chaperonins to mediate ATP-dependent protein folding in a variety of cellular compartments. Chaperonins are evolutionarily conserved and form two distinct classes, namely, group I and group II chaperonins. GroEL and its co-chaperonin GroES form part of group I and are the archetypal members of this family of protein folding machines. The unique mechanism used by GroEL and GroES to drive protein folding is embedded in the complex architecture of double-ringed complexes, forming two central chambers that undergo conformational rearrangements that enable protein folding to occur. GroES forms a lid over the chamber and in doing so dislodges bound substrate into the chamber, thereby allowing non-native proteins to fold in isolation. GroES also modulates allosteric transitions of GroEL. Group II chaperonins are functionally similar to group I chaperonins but differ in structure and do not require a co-chaperonin. A significant number of bacteria and eukaryotes house multiple chaperonin and co-chaperonin proteins, many of which have acquired additional intracellular and extracellular biological functions. In some instances, co-chaperonins display contrasting functions to those of chaperonins. Human HSP60 (HSPD) continues to play a key role in the pathogenesis of many human diseases, in particular autoimmune diseases and cancer. A greater understanding of the fascinating roles of both intracellular and extracellular Hsp10 on cellular processes will accelerate the development of techniques to treat diseases associated with the chaperonin family.

Enhanced serodiagnosis of melioidosis by indirect ELISA using the chimeric protein rGroEL-FLAG300 as an antigen

Background

The accurate and rapid diagnosis of melioidosis is challenging. Several serological approaches have been developed using recombinant antigens to improve the diagnostic indices of serological tests for melioidosis.

Methods

Fusion proteins from Burkholderia pseudomallei (rGroEL-FLAG300) were evaluated as a potential target antigen for melioidosis antibodies. A total of 220 serum samples from 38 culture proven melioidosis patients (gold standard), 126 healthy individuals from endemic (n = 37) and non-endemic (n = 89) Thai provinces and 56 patients with other proven bacterial infections as negative controls were tested using indirect enzyme-linked immunosorbent assays (ELISA).

Results

Using an optical density (OD) cut-off of 0.299148, our assay had 94.74% sensitivity (95% confidence interval (CI) = 82.3–99.4%), 95.05% specificity (95% CI = 90.8–97.7%), and 95% accuracy, which was better than in our previous work (90.48% sensitivity, 87.14% specificity, and 87.63% accuracy).

Conclusion

Our results suggest that the application of chimeric antigens in ELISA could improve the serological diagnosis of melioidosis and should be reconfirmed with greater patient numbers.

Multimodal approaches for the improvement of the cellular folding of a recombinant iron regulatory protein in E. coli

Background

During the recombinant protein expression, most heterologous proteins expressed in E. coli cell factories are generated as insoluble and inactive aggregates, which prohibit E. coli from being employed as an expression host despite its numerous advantages and ease of use. The yeast mitochondrial aconitase protein, which has a tendency to aggregate when expressed in E. coli cells in the absence of heterologous chaperones GroEL/ES was utilised as a model to investigate how the modulation of physiological stimuli in the host cell can increase protein solubility. The presence of folding modulators such as exogenous molecular chaperones or osmolytes, as well as process variables such as incubation temperature, inducer concentrations, growth media are all important for cellular folding and are investigated in this study. This study also investigated how the cell's stress response system activates and protects the proteins from aggregation.

Results

The cells exposed to osmolytes plus a pre-induction heat shock showed a substantial increase in recombinant aconitase activity when combined with modulation of process conditions. The concomitant GroEL/ES expression further assists the folding of these soluble aggregates and increases the functional protein molecules in the cytoplasm of the recombinant E. coli cells.

Conclusions

The recombinant E. coli cells enduring physiological stress provide a cytosolic environment for the enhancement in the solubility and activity of the recombinant proteins. GroEL/ES-expressing cells not only aided in the folding of recombinant proteins, but also had an effect on the physiology of the expression host. The improvement in the specific growth rate and aconitase production during chaperone GroEL/ES co-expression is attributed to the reduction in overall cellular stress caused by the expression host's aggregation-prone recombinant protein expression.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12934-022-01749-w.

Improved high-temperature ethanol production from sweet sorghum juice using Zymomonas mobilis overexpressing groESL genes

Zymomonas mobilis may encounter various types of stress during ethanol fermentation, which reduces ethanol production efficiency. This situation may be mitigated by molecular chaperones, including the chaperonin GroESL, which confers enhanced protection against various stresses. In this study, we successfully developed a Z. mobilis strain R301 that harbors groESL genes and can be used for high-temperature ethanol production from sweet sorghum juice. Sequence analyses of GroES and GroEL from Z. mobilis TISTR548 demonstrated conserved residues at specific positions within GroES and conserved glycine-glycine-methionine (GGM) repeats at the C-terminus of GroEL. The Z. mobilis wild-type and R301 strains were then evaluated for their tolerance to stresses, including high temperatures, high sugar concentrations, and high ethanol concentrations up to 40°C, 300 g/L, and 13% (v/v), respectively. Z. mobilis R301 exhibited better growth performance than the wild-type strain under all stress conditions. This is the first report on ethanol production at 40°C by recombinant Z. mobilis using sweet sorghum juice; this strain produced an ethanol concentration of 41.66 g/L, with a productivity of 0.87 g/L/h and a theoretical ethanol yield of 88.9%. Overexpression of groESL resulted in increased ethanol production, with values approximately 11% higher than those of the wild type at 40°C. Additionally, at 37°C, Z. mobilis R301 gave a higher theoretical ethanol yield (92.6%) than that shown in previous research. This work illustrates the potential for future enhancement of industrial-scale ethanol production at high temperatures utilizing Z. mobilis R301 in the bioconversion of sweet sorghum juice, a promising energy crop. KEY POINTS: • The groESL-overexpressing Z. mobilis strain was successfully constructed. • The recombinant Z. mobilis exhibited higher stress tolerance than the wild-type strain. • Overexpression of groESL genes improved ethanol production efficiency at high temperatures.

Optimized expression of Hfq protein increases Escherichia coli growth

Escherichia coli is a widely used platform for metabolic engineering due to its fast growth and well-established engineering techniques. However, there has been a demand for faster-growing E. coli for higher production of desired substances. Here, to increase the growth of E. coli cells, we optimized the expression level of Hfq protein, which plays an essential role in stress responses. Six variants of the hfq gene with a different ribosome binding site sequence and thereby a different expression level were constructed. When the Hfq expression level was optimized in DH5α, its growth rate was increased by 12.1% and its cell density was also increased by 4.5%. RNA-seq and network analyses revealed the upregulation of stress response genes and metabolic genes, which increases the tolerance against pH changes. When the same strategy was applied to five other E. coli strains (BL21 (DE3), JM109, TOP10, W3110, and MG1655), all their growth rates were increased by 18-94% but not all their densities were increased (- 12 - + 32%). In conclusion, the Hfq expression optimization can increase cell growth rate and probably their cell densities as well. Since the hfq gene is highly conserved across bacterial species, the same strategy could be applied to other bacterial species to construct faster-growing strains.

Coordinated Expression of Astaxanthin Biosynthesis Genes for Improved Astaxanthin Production in Escherichia coli

Astaxanthin has great potential commercial value in the feed, cosmetics, and nutraceutical industries due to its strong antioxidant capacity. In this study, the Escherichia coli strain CAR026 with completely balanced metabolic flow was selected as the starting strain for the production of astaxanthin. The expression of β-carotene ketolase (CrtW) and β-carotene hydroxylase (CrtZ), which catalyze the conversion of β-carotene to astaxanthin, was coordinated, and a bottleneck was eliminated by increasing the copy number of crtY in CAR026. The resulting strain Ast007 produced 21.36 mg/L and 4.6 mg/g DCW of astaxanthin in shake flasks. In addition, the molecular chaperone genes groES-groEL were regulated to further improve the astaxanthin yield. The best strain Gro-46 produced 26 mg/L astaxanthin with a yield of 6.17 mg/g DCW in shake flasks and 1.18 g/L astaxanthin after 60 h of fermentation under fed-batch conditions. To the best of our knowledge, this is the highest astaxanthin obtained using engineered E. coli to date.

Cytoplasmic Chaperones Enhance Soluble Expression of Anti-EGFR huscFv in Escherichia coli

Background:

Overexpression of EGFR is associated with carcinogenesis in more than 70% of head and neck cancers. Anti-EGFR monoclonal antibodies bind to the extracellular domain of EGFR and block the EGFR downstream signaling pathway, which results in the suppression of the growth of the tumor cells. Escherichia coli is the preferred system for expressing various recombinant proteins, including single chain antibodies, but the formation of inclusion bodies negatively affects the efficacy of this system. Several strategies have been suggested to solve this problem, notably the utilization of molecular chaperones.

Objectives:

In this study, we attempted to increase the soluble expression of huscfv antibody via co-expression with the cytoplasmic chaperones.

Materials and Methods:

To achieve this purpose, chaperones plasmids pG-KJE8, pGro7, pKjE7, pTf16 and pG-Tf2 encoding cytoplasmic chaperones were co-expressed with the humanized anti-EGFR scFv construct in E. coli. Different temperatures, incubations times, and concentrations of IPTG were used to produce an active antibody with the highest solubility. Results were analyzed by SDS-PAGE. Soluble huscFv was purified by Ni-NTA column and the biologic activity of the recombinant protein was determined by ELISA.

Result:

The results indicated that the highest concentrations of humanized anti-EGFR scFv were obtained by co-expression of huscFv via chaperone plasmid pG-KJE8 with 0.2 mM concentration of inducer (IPTG), culture temperature of 25 °C, and 4 h incubation time after induction.

Conclusion:

In conclusion, co-expression with chaperones could be used as an efficient strategy to produce soluble active ScFvs in E. coli.

An ancient family of mobile genomic islands introducing cephalosporinase and carbapenemase genes in Enterobacteriaceae

The exchange of mobile genomic islands (MGIs) between microorganisms is often mediated by phages, which may provide benefits to the phage’s host. The present study started with the identification of Enterobacter cloacae, Klebsiella pneumoniae and Escherichia coli isolates with exceptional cephalosporin and carbapenem resistance phenotypes from patients in a neonatal ward. To identify possible molecular connections between these isolates and their β-lactam resistance phenotypes, the respective bacterial genome sequences were compared. This unveiled the existence of a family of ancient MGIs that were probably exchanged before the species E. cloacae, K. pneumoniae and E. coli emerged from their common ancestry. A representative MGI from E. cloacae was named MIR17-GI, because it harbors the novel β-lactamase gene variant bla_MIR17. Importantly, our observations show that the MIR17-GI-like MGIs harbor genes associated with high-level resistance to cephalosporins. Among them, MIR17-GI stands out because MIR17 also displays carbapenemase activity. As shown by mass spectrometry, the MIR17 carbapenemase is among the most abundantly expressed proteins of the respective E. cloacae isolate. Further, we show that MIR17-GI-like islands are associated with integrated P4-like prophages. This implicates phages in the spread of cephalosporin and carbapenem resistance amongst Enterobacteriaceae. The discovery of an ancient family of MGIs, mediating the spread of cephalosporinase and carbapenemase genes, is of high clinical relevance, because high-level cephalosporin and carbapenem resistance have serious implications for the treatment of patients with enterobacteriaceal infections.

Revisiting Escherichia coli as microbial factory for enhanced production of human serum albumin

BACKGROUND

Human serum albumin (HSA)-one of the most demanded therapeutic proteins with immense biotechnological applications-is a large multidomain protein containing 17 disulfide bonds. The current source of HSA is human blood plasma which is a limited and unsafe source. Thus, there exists an indispensable need to promote non-animal derived recombinant HSA (rHSA) production. Escherichia coli is one of the most convenient hosts which had contributed to the production of more than 30% of the FDA approved recombinant pharmaceuticals. It grows rapidly and reaches high cell density using inexpensive and simple subst-rates. E. coli derived recombinant products have more economic potential as fermentation processes are cheaper compared to the other expression hosts. The major bottleneck in exploiting E. coli as a host for a disulfide-rich multidomain protein is the formation of aggregates of overexpressed protein. The majority of the expressed HSA forms inclusion bodies (more than 90% of the total expressed rHSA) in the E. coli cytosol. Recovery of functional rHSA from inclusion bodies is not preferred because it is difficult to obtain a large multidomain disulfide bond rich protein like rHSA in its functional native form. Purification is tedious, time-consuming, laborious and expensive. Because of such limitations, the E. coli host system was neglected for rHSA production for the past few decades despite its numerous advantages.

RESULTS

In the present work, we have exploited the capabilities of E. coli as a host for the enhanced functional production of rHSA (~ 60% of the total expressed rHSA in the soluble fraction). Parameters like intracellular environment, temperature, induction type, duration of induction, cell lysis conditions etc. which play an important role in enhancing the level of production of the desired protein in its native form in vivo have been optimized. We have studied the effect of assistance of different types of exogenously employed chaperone systems on the functional expression of rHSA in the E. coli host system. Different aspects of cell growth parameters during the production of rHSA in presence and absence of molecular chaperones in E. coli have also been studied.

CONCLUSION

In the present case, we have filled in the gap in the literature by exploiting the E. coli host system, which is fast-growing and scalable at the low cost of fermentation, as a microbial factory for the enhancement of functional production of rHSA, a crucial protein for therapeutic and biotechnological applications.

Cloning and characterization of thermostable GroEL/GroES homologues from Geobacillus thermopakistaniensis and their applications in protein folding

The chaperonin genes encoding GroEL_Gt (ESU72018) and GroES_Gt (ESU72017), homologues of bacterial GroEL and GroES, from Geobacillus thermopakistaniensis were cloned and expressed in Escherichia coli. The purified gene products possessed the ATPase activity similar to other bacterial and eukaryal counterparts. Recombinant GroEL_Gt and GroES_Gt were able to refold the denatured insoluble aggregates of α-amylase from Bacillus licheniformis into soluble and active form. Furthermore, GroEL_Gt and GroES_Gt successfully enhanced the thermostability of porcine heart malate dehydrogenase. Expression of GroEL_Gt gene in E. coli cells enhanced the thermotolerance of the host. Furthermore, soluble production of recombinant alcohol dehydrogenase from Bacillus subtilis strain R5 in E. coli, initially produced as insoluble aggregates, was achieved by co-expressing the gene with GroEL_Gt. Our results implied that GroEL_Gt could assist folding of nascent protein in E. coli with the help of host co-chaperonin without requiring additional ATP. This system can be used for soluble production of recombinant proteins which otherwise are produced in insoluble form in E. coli. To the best of our knowledge this is the first report on functional characterization and applications of chaperonins from genus Geobacillus.

Enhancing the Yield of Active Recombinant Chitobiase by Physico-Chemical and In Vitro Refolding Studies

Chitobiase (CHB) is an important enzyme for the production of N-acetyl-D-glucosamine from the chitin biopolymer in the series of chitinolytic enzymes. Majority of over-expressed CHB (58%) in E. coli expression system led to formation of inclusion bodies. The production and soluble yield of active CHB was enhanced by co-expression with GroEL/ES chaperonin, optimizing culture conditions and solubilization followed by refolding of remaining inactive chitobiase present in the form of inclusion bodies. The growth of recombinant E. coli produced 42% CHB in soluble form and the rest (~58%) as inclusion bodies. The percentage of active CHB was enhanced to 71% by co-expression with GroEL/ES chaperonin system and optimizing culture conditions (37 °C, 200 rpm, IPTG--0.5 mM, L-arabinose--13.2 mM). Of the remaining inactive CHB present in inclusion bodies, 37% could be recovered in active form using pulsatile dilution method involving denaturants (2 M urea, pH 12.5) and protein refolding studies (1.0 M L-arginine, 5% glycerol). Using combinatorial approach, 80% of the total CHB expressed, could be recovered from cells grown in one litre of LB medium is a step forward in replacing hazardous chemical technology by biotechnological process for the production of NAG from chitinous waste.

Dispensability of the [4Fe-4S] cluster in novel homologues of adenine glycosylase MutY

7,8-Dihydro-8-deoxyguanine (8oG) is one of the most common oxidative lesions in DNA. DNA polymerases misincorporate an adenine across from this lesion. Thus, 8oG is a highly mutagenic lesion responsible for G:C→T:A transversions. MutY is an adenine glycosylase, part of the base excision repair pathway that removes adenines, when mispaired with 8oG or guanine. Its catalytic domain includes a [4Fe-4S] cluster motif coordinated by cysteinyl ligands. When this cluster is absent, MutY activity is depleted and several studies concluded that the [4Fe-4S] cluster motif is an indispensable component for DNA binding, substrate recognition and enzymatic activity. In the present study, we identified 46 MutY homologues that lack the canonical cysteinyl ligands, suggesting an absence of the [4Fe-4S] cluster. A phylogenetic analysis groups these novel MutYs into two different clades. One clade is exclusive of the order Lactobacillales and another clade has a mixed composition of anaerobic and microaerophilic bacteria and species from the protozoan genus Entamoeba. Structural modeling and sequence analysis suggests that the loss of the [4Fe-4S] cluster is compensated by a convergent solution in which bulky amino acids substitute the [4Fe-4S] cluster. We functionally characterized MutYs from Lactobacillus brevis and Entamoeba histolytica as representative members from each clade and found that both enzymes are active adenine glycosylases. Furthermore, chimeric glycosylases, in which the [4Fe-4S] cluster of Escherichia coli MutY is replaced by the corresponding amino acids of LbY and EhY, are also active. Our data indicates that the [4Fe-4S] cluster plays a structural role in MutYs and evidences the existence of alternative functional solutions in nature.

Chaperone-Assisted Soluble Expression of a Humanized Anti-EGFR ScFv Antibody in E. Coli

PURPOSE

Formation of inclusion bodies is a considerable obstacle threatening the advantages of E. coli expression system to serve as the most common and easiest system in recombinant protein production. To solve this problem, several strategies have been proposed among which application of molecular chaperones is of remarkable consideration. The aim of this study was to evaluate the effects of molecular chaperones on soluble expression of aggregation-prone humanized single chain antibody.

METHODS

To increase the solubility of a humanized single chain antibody (hscFv), different chaperone plasmids including PG-tf2 (GroES- GroEL- tig), ptf16 (tig) and pGro7 (GroES- GroEL) were co-expressed in BL21 cells containing pET-22b- hscFv construct. The solubility of recombinant hscFv was analyzed by SDS-PAGE. After purification of soluble hscFv by Ni-NTA column, the biological activity and cytotoxicity of the recombinant protein were tested by ELISA and MTT assay, respectively.

RESULTS

SDS-PAGE analysis of the hscFv revealed that chaperone utility remarkably increased (up to 50%) the solubility of the protein. ELISA test and MTT assay analyses also confirmed the biological activity of the gained hscFv in reaction with A431 cells (OD value: 2.6) and inhibition of their proliferation, respectively.

CONCLUSION

The results of this study revealed that co-expression of chaperones with hscFv leads to remarkable increase in the solubility of the recombinant hscFv, which could be of great consideration for large scale production of recombinant single chain antibodies.

Chaperonin-co-chaperonin interactions

Co-chaperonins function together with chaperonins to mediate ATP-dependant protein folding in a variety of cellular compartments. GroEL and its co-chaperonin GroES are the only essential chaperones in Escherichia coli and are the archetypal members of this family of protein folding machines. The unique mechanism used by GroEL and GroES to drive protein folding is embedded in the complex architecture of double-ringed complexes, forming two central chambers that undergo structural rearrangements as part of the folding mechanism. GroES forms a lid over the chamber, and in doing so dislodges bound substrate into the chamber, thereby allowing non-native proteins to fold in isolation. GroES also modulates allosteric transitions of GroEL. A significant number of bacteria and eukaryotes house multiple chaperonin and co-chaperonin proteins, many of which have acquired additional intracellular and extracellular biological functions. In some instances co-chaperonins display contrasting functions to those of chaperonins. Human Hsp60 continues to play a key role in the pathogenesis of many human diseases, in particular autoimmune diseases and cancer. A greater understanding of the fascinating roles of both intracellular and extracellular Hsp10, in addition to its role as a co-chaperonin, on cellular processes will accelerate the development of techniques to treat diseases associated with the chaperonin family.

Production of soluble recombinant proteins in Escherichia coli: effects of process conditions and chaperone co-expression on cell growth and production of xylanase

In this study, effects of temperature, inducer concentration, time of induction and co-expression of molecular chaperones (GroEL-GroES and DnaKJE), on cell growth and solubilization of model protein, xylanases, were investigated. The yield of soluble xylanases increased with decreasing cultivation temperature and inducer level. In addition, co-expression of DnaKJE chaperone resulted in increased soluble xylanases though the time of induction of chaperone and target protein had a bearing on this yield. A combination of chaperone co-expression and partial induction resulted in ∼40% (in DnaKJE) and 33% (in GroEL-GroES) of total xylanase yield in soluble fraction. However, the conditions for maximum yield of soluble r-XynB and maximum % soluble expression of r-XynB were different. Higher expression of soluble xylanases in a scalable semi-synthetic medium showed potential of the process for soluble enzyme production.

Molecular functions of chaperonin gene, containing tailless complex polypeptide 1 from Macrobrachium rosenbergii

Chaperonin (MrChap) was identified from a constructed transcriptome dataset of freshwater prawn Macrobrachium rosenbergii. The MrChap peptide contains a long chaperone super family domain between 11 and 525. Three chaperone tailless complex polypeptide (TCP-1) signatures are present in the MrChap peptide sequence at 36-48, 57-73 and 85-93. The gene expressions of MrChap in both healthy M. rosenbergii and those infected with infectious hypodermal and hematopoietic necrosis virus (IHHNV) were examined using qRT-PCR. To understand its biological activity, the recombinant MrChap gene was constructed and expressed in Escherichia coli BL21 (DE3). The results of ATPase assay showed that the recombinant MrChap protein exhibited apparent ATPase activity. Chaperone activity assay showed that the recombinant MrChap protein is an active chaperone. These results suggest that MrChap is potentially involved in the immune responses against viral infection in M. rosenbergii. These findings indicate that the recombinant MrChap protein may be used in immunotherapeutic approaches.

Mutagenesis of RpoE-like sigma factor genes in Bdellovibrio reveals differential control of groEL and two groES genes

BACKGROUND

Bdellovibrio bacteriovorus HD100 must regulate genes in response to a variety of environmental conditions as it enters, preys upon and leaves other bacteria, or grows axenically without prey. In addition to "housekeeping" sigma factors, its genome encodes several alternate sigma factors, including 2 Group IV-RpoE-like proteins, which may be involved in the complex regulation of its predatory lifestyle.

RESULTS

We find that one sigma factor gene, bd3314, cannot be deleted from Bdellovibrio in either predatory or prey-independent growth states, and is therefore possibly essential, likely being an alternate sigma 70. Deletion of one of two Group IV-like sigma factor genes, bd0881, affects flagellar gene regulation and results in less efficient predation, although not due to motility changes; deletion of the second, bd0743, showed that it normally represses chaperone gene expression and intriguingly we find an alternative groES gene is expressed at timepoints in the predatory cycle where intensive protein synthesis at Bdellovibrio septation, prior to prey lysis, will be occurring.

CONCLUSIONS

We have taken the first step in understanding how alternate sigma factors regulate different processes in the predatory lifecycle of Bdellovibrio and discovered that alternate chaperones regulated by one of them are expressed at different stages of the lifecycle.

Overexpression of mouse estrogen receptor-β decreases but its transactivation and ligand binding domains increase the growth characteristics of E. coli

Escherichia coli is one of the most common and widely used prokaryotic hosts for the expression of recombinant proteins. The overexpression of recombinant proteins occasionally increases bacterial growth but sometimes reduces it and becomes lethal to the host cells. Here, we report the overexpression of mouse ER-β and its domains in the prokaryotic expression system and its opposite effect on the growth characteristics of E. coli. ER-β protein was immunologically detected as a 53 kDa his-tag protein in the pellet of the bacterial lysate. Its overexpression, as reflected by the total protein content and expression pattern, resulted in the decrease of bacterial growth. However, the overexpression of ER-β transactivation domain (TAD) using pIVEX and ligand binding domain (LBD) using pRSETA in E. coli BL21 (DE3) show opposite pattern. TAD was immunologically detected as 20 kDa and LBD as 22 kDa protein in the supernatant of the bacterial lysate and their overexpression increased the bacterial growth.

Sense and nonsense from a systems biology approach to microbial recombinant protein production

The 'Holy Grail' of recombinant protein production remains the availability of generic protocols and hosts for the production of even the most difficult target products. The present review provides first an explanation why the shock imposed on bacteria using a standard induction protocol not only arrests growth, but also decreases the number of colony-forming units by several orders of magnitude. Particular emphasis is placed on findings of numerous genome-wide transcriptomic studies that highlight cellular stress, in which the general stress, heat-shock and stringent responses are the underlying basis for the manifestation of the deterioration of cell physiology. We then review common approaches used to solve bottlenecks in protein folding and post-translational modification that result in recombinant protein deposition in cytoplasmic inclusion bodies. Finally, we suggest a generic approach to process design that minimizes stress on the production host and a strategy for isolating improved hosts.

Identification of promoter-binding proteins of the fbp A and C genes in Mycobacterium tuberculosis

The antigen 85 (Ag85) complex of Mycobacterium tuberculosis represents a promising candidate as a novel drug target and pathogenesis factor. Ag85 comprises three proteins Ag85A, B and C, (encoded by the genes fbpA, B, and C), which participate in cell wall biosynthesis, and interact with the host macrophage as fibronectin-binding proteins (fbps). Ag85 is also involved in the response to isoniazid (INH) treatment. The objective of this study was to identify potential fbp gene activators involved in the over-expression of fbp genes in response to INH. The biotinylated upstream promoter regions of fbpA and fbpC were used together with streptavidin-coated magnetic beads in DNA-binding assays, to isolate proteins with high-binding affinities from cytosolic extracts of INH-treated M. tuberculosis. Resolution of the DNA-binding proteins by 1D SDS-PAGE revealed 6 proteins with high-affinity for the fbpA promoter, and 7 with specificity the fbpC promoter. Mass spectrometric analyses [LC-ES(MS/MS)] identified proteins associated with drug resistance and stress/treatment responses, intermediary metabolism and cellular division, hypothetical proteins including a member of the MarR family of bacterial transcriptional regulators. The DNA-binding MarR protein shows potential as an authentic activator of fbp genes and functional validation of this factor is warranted.

Enhancement of over expression and chaperone assisted yield of folded recombinant aconitase in Escherichia coli in bioreactor cultures

A major portion of the over expressed yeast mitochondrial aconitase, a large 82 kDa monomeric TCA cycle enzyme, in Escherichia coli led to the formation of inclusion bodies. Bacterial chaperonin GroEL mediated the correct folding of aconitase with the assistance of its co-chaperonin GroES in an ATP dependent manner. Till date the chaperonin assisted folding of aconitase was limited to the shake flask studies with relatively low yields of folded aconitase. No attempt had yet been made to enhance the yield of chaperone mediated folding of aconitase using a bioreactor. The current report deals with the effect of co-expression of GroEL/GroES in the production of soluble, biologically active recombinant aconitase in E. coli by cultivation in a bioreactor at different temperatures under optimized conditions. It revealed that the yield of functional aconitase was enhanced, either in presence of co-expressed GroEL/ES or at low temperature cultivation. However, the outcome from the chaperone assisted folding of aconitase was more pronounced at lower temperature. A 3-fold enhancement in the yield of functional aconitase from the bioreactor based chaperone assisted folding was obtained as compared to the shake flask study. Hence, the present study provides optimized conditions for increasing the yield of functional aconitase by batch cultivation in a bioreactor.

Use of folding modulators to improve heterologous protein production in Escherichia coli

Despite the fundamental importance of E. coli in the manufacture of a wide range of biotechnological and biomedical products, extensive process and/or target optimisation is routinely required in order to achieve functional yields in excess of low mg/l levels. Molecular chaperones and folding catalysts appear to present a panacea for problems of heterologous protein folding in the organism, due largely to their broad substrate range compared with, e.g., protein-specific mutagenesis approaches. Painstaking investigation of chaperone overproduction has, however, met with mixed - and largely unpredictable - results to date. The past 5 years have nevertheless seen an explosion in interest in exploiting the native folding modulators of E. coli, and particularly cocktails thereof, driven largely by the availability of plasmid systems that facilitate simultaneous, non-rational screening of multiple chaperones during recombinant protein expression. As interest in using E. coli to produce recombinant membrane proteins and even glycoproteins grows, approaches to reduce aggregation, delay host cell lysis and optimise expression of difficult-to-express recombinant proteins will become even more critical over the coming years. In this review, we critically evaluate the performance of molecular chaperones and folding catalysts native to E. coli in improving functional production of heterologous proteins in the bacterium and we discuss how they might best be exploited to provide increased amounts of correctly-folded, active protein for biochemical and biophysical studies.