Characterization of a New Bacillus thuringiensis Isolate Highly Active Against Cochylis hospes

A new bacterial isolate, 00-50-5, from sunflower head extracts was identified as Bacillus thuringiensis (Bt) according to its morphology. Bt isolate 00-50-5 was highly active against the banded sunflower moth (BSM), Cochylis hospes Walsingham. A sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) 4–15% gradient gel of whole strain protein of 00-50-5 revealed six proteins with molecular masses (M_r) of 133, 80, 60, 27, 15, and 14 kDa. SDS-PAGE of pH 4.2-precipitated proteins (PP) or activated proteins formed by adding the BSM larval gut protease at 1:50 (wt/wt, protease/PP) showed five bands, including two major proteins of M_r 60 kDa and 27 kDa, and three small peptides of M_r 15, 13, and 7 kDa. The BSM larval gut protease was able to completely digest the proteins when present at a high ratio (10:1, wt/wt, protease/PP). The 60- and 27-kDa proteins could be digested by subtilisin Carlsberg at ratios of 1:50 or 1:1 (wt/wt, protease/PP), but neither BSM larval gut protease nor trypsin was effective at the same ratios. Three small peptides of M_r 15, 13, and 7 kDa were digested by the gut protease at a ratio of 1:1 (wt/wt). The N-terminal sequence of 1–31 amino acid residues for the 27-kDa protein showed 96.7% homology to a 31-amino acid fragment from camelysin, a protease from B. cereus, indicating that the 27-kDa protein may be a camelysin and a novel active protein against BSM. Received: 9 July 2001 / Accepted: 8 August 2001     

A system for purification of recombinant proteins in Escherichia coli via artificial oil bodies constituted with their oleosin-fused polypeptides

An expression/purification system was developed using artificial oil bodies (AOB) as carriers for producing recombinant proteins. A target protein, green fluorescent protein (GFP), was firstly expressed in Escherichia coli as an insoluble recombinant protein fused to oleosin, a unique structural protein of seed oil bodies, by a linker sequence susceptible to factor Xa cleavage. Artificial oil bodies were constituted with triacylglycerol, phospholipid, and the insoluble recombinant protein, oleosin-Xa-GFP. After centrifugation, the oleosin-fused GFP was exclusively found on the surface of artificial oil bodies presumably with correct folding to emit fluorescence under excitation. Proteolytic cleavage with factor Xa separated soluble GFP from oleosin embedded in the artificial oil bodies; thus after re-centrifugation, GFP of high yield and purity was harvested simply by concentrating the ultimate supernatant.     

Generation of catalytic protein particles in <Emphasis Type="Italic">Escherichia coli</Emphasis> cells using the cellulose-binding domain from <Emphasis Type="Italic">Cellulomonas fimi</Emphasis> as a fusion partner

The cellulose-binding domain (CBD) of a Cellulomonas fimi exo-glucanase was translationally fused with β-glucuronidase (GusA) from Escherichia coli and β-glycosidase (BglA) from Thermus caldophilus, respectively. Two fusion proteins (GusA-CBD and BglA-CBD) were expressed as insoluble aggregates in cells and isolated by centrifugation of the cell lysates. Interestingly, activity assays revealed that > 90% of the catalytic activity of both proteins was localized in the insoluble fractions. For example, the GusA-CBD particles exhibited 21 units per mg protein, which corresponded to 19% specific activity of the highly purified soluble GusA. The specific activity increased further up to 42 units per mg protein when treated with either sonication or chaotropic L-arginine. These results demonstrate that fusion with CBD family II may activate catalytic protein particles in E. coli cells, and that internal proteins of the particles are also active. Finally, the protein particles were tested in repeated batch operations after being cross-linked with chemicals, indicating that they have potential as a new preparation for immobilized biocatalysts.     

Characterization of microemulsion structures in the pseudoternary phase diagram of isopropyl palmitate/water/Brij 97:1-butanol

This research was aimed to characterize microemulsion systems of isopropyl palmitate (IPP), water, and 2∶1 Brij 97 and 1-butanol by different experimental techniques. A pseudoternary phase diagram was constructed using water titration method. At 45% wt/wt surfactant system, microemulsions containing various ratios of water and IPP were prepared and identified by electrical conductivity, viscosity, differential scanning calorimetry (DSC), cryo-field emission scanning electron microscopy (cryo-FESEM) and nuclear magnetic resonance (NMR). The results from conductivity and viscosity suggested a percolation transition from water-in-oil (water/oil) to oil-in-water (oil/water) microemulsions at 30% wt/wt water. From DSC results, the exothermic peak of water and the endothermic peak of IPP indicated that the transition of water/oil to oil/water microemulsions occurred at 30% wt/wt water. Cryo-FESEM photomicrographs revealed globular structures of microemulsions at higher than 15% wt/wt water. In addition, self-diffusion coefficients determined by NMR reflected that the diffusability of water increased at higher than 35% wt/wt water, while that of IPP was in reverse. Therefore, the results from all techniques are in good agreement and indicate that the water/oil and oil/water transition point occurred in the range of 30% to 35% wt/wt water.     

Enzymatic preparation of 1,6-anhydro-muropeptides by immobilized murein hydrolases from Escherichia coli fused to staphylococcal protein A

Summary In order to produce biologically active 1,6-anhydro-muropeptides in large amounts by enzymatic degradation of isolated bacterial murein polymer highly specific periplasmic murein-metabolizing enzymes from Escherichia coli are made available. The genes slt, dacB, and mepA, encoding the soluble lytic transglycosylase (Slt), the penicillin-sensitive DD-endopeptidase (PBP4), and the penicillin-insensitive murein endopeptidase A (MepA), were independently fused to the N-terminal encoding sequence of staphylococcal protein A (SpA) under control of the temperature-inducible phage p _R promoter. The SpA fusion proteins were stably over-produced at high levels in E. coli upon temperature induction at 42°C and account for 3% (5 mg SpASlt/l culture), 3% (5 mg SpAPBP4/l culture), and 0.3% (0.5 mg SpAMepA/l culture) of total protein. The SpA fusion proteins, immobilized on IgG Sepharose, are proteolytically sensitive, in vitro, resulting in complete degradation of the SpA portion of the fusion proteins and release of the murein hydrolases in intact and enzymatically active form into the supernatant. Proteolytic degradation could be prevented by p-hydroxymercuribenzoic acid (PHMB) or ethylenediaminetetraacetate (EDTA) suggesting the involvement of the periplasmic protease Pi from E. coli. The immobilized fusion proteins were enzymatically active and could be used for the batch production of biologically active 1,6-anhydro-muropeptides, which were successively separated on HPLC. Isolated murein polymer was degraded quantitatively to monomeric 1,6-anhydro-muropeptides when immunoglobulin G (IgG)-SpASlt was used in combination with IgG-SpAMepA. A combination of IgG-SpASlt with IgG-SpAPBP4 left the 1,6-anhydro-dimers and oligomers being cross-linked via an LD-peptide bond (m-DAP-m-DAP) uncleaved. Correspondence to: W. Keck     

Effects of l-arginine on refolding of lysine-tagged human insulin-like growth factor 1 expressed in Escherichia coli

Insulin-like growth factor 1 (IGF1), a therapeutic protein, is highly homologous to proinsulin in 3-dimensional structure. To highly express IGF1 in recombinant Escherichia coli, IGF1 was engineered to be fused with the 6-lysine tag and ubiquitin at its N-terminus (K6Ub-IGF1). Fed-batch fermentation of E. coli TG1/pAPT-K6Ub-IGF1 resulted in 60.8 g/L of dry cell mass, 18% of which was inclusion bodies composed of K6Ub-IGF1. Subsequent refolding processes were conducted using accumulated inclusion bodies. An environment of 50 mM bicine buffer (pH 8.5), 125 mM L-arginine, and 4 °C was chosen to optimize the refolding of K6Ub-IGF1, and 240 mg/L of denatured K6Ub-IGF1 was refolded with a 32% yield. The positive effect of L-arginine on K6Ub-IGF1 refolding might be ascribed to preventing unfolded K6Ub-IGF1 from undergoing self-aggregation and thus increasing its solubility. The simple dilution refolding, followed by cleavage of the fusion protein by site-specific UBP1 and chromatographic purification of IGF1, led production of authentic IGF1 with 97% purity and an 8.5% purification yield, starting from 500 mg of inclusion bodies composed of K6Ub-IGF1, as verified by various analytical tools, such as RP-HPLC, CD spectroscopy, MALDI-TOF mass spectrometry, and Western blotting. Thus, it was confirmed that L-arginine with an aggregation-protecting ability could be applied to the development of refolding processes for other inclusion body-derived proteins.     

Long-term fertilization regimes change soil nitrification potential by impacting active autotrophic ammonia oxidizers and nitrite oxidizers as assessed by DNA stable isotope probing

Chemoautotrophic ammonia-oxidizers and nitrite-oxidizers are responsible for a significant amount of soil nitrate production. The identity and composition of these active nitrifiers in soils under different long-term fertilization regimes remain largely under-investigated. Based on that soil nitrification potential significantly decreased in soils with chemical fertilization (CF) and increased in soils with organic fertilization (OF), a microcosm experiment with DNA stable isotope probing was further conducted to clarify the active nitrifiers. Both ammonia-oxidizing archaea (AOA) and bacteria (AOB) were found to actively respond to urea addition in soils with OF and no fertilizer (CK), whereas only AOB were detected in soils with CF. Around 98% of active AOB were Nitrosospira cluster 3a.1 in all tested soils, and more than 90% of active AOA were Nitrososphaera subcluster 1.1 in unfertilized and organically fertilized soils. Nitrite oxidation was performed only by Nitrospira-like bacteria in all soils. The relative abundances of Nitrospira lineage I and VI were 32% and 61%, respectively, in unfertilized soils, and that of Nitrospira lineage II was 97% in fertilized soils, indicating long-term fertilization shifted the composition of active Nitrospira-like bacteria in response to urea. This finding indicates that different fertilizer regimes impact the composition of active nitrifiers, thus, impacting soil nitrification potential.     

Expression of honeybee prepromelittin as a fusion protein in Escherichia coli

Strategies for the expression of precursors of eukaryotic secreted proteins as part of fused proteins in Escherichia coli have been explored. A fusion protein with β-galactosidase at the N-terminal end and honeybee prepromelittin at the C-terminal end (β-gal-pM) was expressed in low amounts as a cleaved polypeptide, from which the promelittin portion had been removed. Inclusion in the induction culture of 10 mM MgCl₂ or 8.3% (v/v) ethanol, inhibitors of signal peptidase, gave rise to the full-length β-gal-pM fusion protein. The results suggest that a soluble recombinant fusion protein with a signal peptide in an internal location 660 residues from the N-terminus is recognized by the E. coli translocation apparatus in the inner membrane and by leader peptidase. High-level production (about 45% of total cellular proteins) of prepromelittin was achieved when it was part of a fusion protein at the C-terminus of a truncated insoluble polypeptide from bacteriophage gene 10. This fusion protein separated into inclusion bodies in an aggregated form. In contrast, attempts to express prepromelittin by itself or at the N-terminal end of a fusion with mouse dihydrofolate reductase (pM-DHFR) proved unsuccessful.     

Inoculum effects on community composition and nitritation performance of autotrophic nitrifying biofilm reactors with counter‐diffusion geometry

The link between nitritation success in a membrane‐aerated biofilm reactor (MABR) and the composition of the initial ammonia‐ and nitrite‐oxidizing bacterial (AOB and NOB) population was investigated. Four identically operated flat‐sheet type MABRs were initiated with two different inocula: from an autotrophic nitrifying bioreactor (Inoculum A) or from a municipal wastewater treatment plant (Inoculum B). Higher nitritation efficiencies (NO₂^‐‐N/NH₄⁺‐N) were obtained in the Inoculum B‐ (55.2–56.4%) versus the Inoculum A‐ (20.2–22.1%) initiated reactors. The biofilms had similar oxygen penetration depths (100–150 µm), but the AOB profiles [based on 16S rRNA gene targeted real‐time quantitative PCR (qPCR)] revealed different peak densities at or distant from the membrane surface in the Inoculum B‐ versus A‐initiated reactors, respectively. Quantitative fluorescence in situ hybridization (FISH) revealed that the predominant AOB in the Inoculum A‐ and B‐initiated reactors were Nitrosospira spp. (48.9–61.2%) versus halophilic and halotolerant Nitrosomonas spp. (54.8–63.7%), respectively. The latter biofilm displayed a higher specific AOB activity than the former biofilm (1.65 fmol cell^?1 h^?1 versus 0.79 fmol cell^?1 h^?1). These observations suggest that the AOB and NOB population compositions of the inoculum may determine dominant AOB in the MABR biofilm, which in turn affects the degree of attainable nitritation in an MABR.     

Simple purification ofEscherichia coli-derived recombinant human interleukin-2 expressed with N-terminus fusion of glucagon

Simple procedures have been devised for purifying recombinant human interleukin-2 (hIL-2), which was expressed inEscherichia coli using sequences of glucagon molecules and enterokinase cleavage site as an N-terminus fusion partner. The insoluble aggregates of recombinant fusion protein produced inE. coli cytoplasm were easily dissolved by simple alkaline pH shift (8→12→8). Following enterokinase cleavage, the recombinant hIL-2 was finally purified by one-step reversed-phase HPLC with high purity. The ease and high efficiency of this simple purification process seem to mainly result from the role of used glucagon fusion partner, which could be applied to the production of other therapeutically important proteins.     

New fusion protein systems designed to give soluble expression in Escherichia coli.

Three native E. coli proteins-NusA, GrpE, and bacterioferritin (BFR)-were studied in fusion proteins expressed in E. coli for their ability to confer solubility on a target insoluble protein at the C-terminus of the fusion protein. These three proteins were chosen based on their favorable cytoplasmic solubility characteristics as predicted by a statistical solubility model for recombinant proteins in E. coli. Modeling predicted the probability of soluble fusion protein expression for the target insoluble protein human interleukin-3 (hIL-3) in the following order: NusA (most soluble), GrpE, BFR, and thioredoxin (least soluble). Expression experiments at 37 degrees C showed that the NusA/hIL-3 fusion protein was expressed almost completely in the soluble fraction, while GrpE/hIL-3 and BFR/hIL-3 exhibited partial solubility at 37 degrees C. Thioredoxin/hIL-3 was expressed almost completely in the insoluble fraction. Fusion proteins consisting of NusA and either bovine growth hormone or human interferon-gamma were also expressed in E. coli at 37 degrees C and again showed that the fusion protein was almost completely soluble. Starting with the NusA/hIL-3 fusion protein with an N-terminal histidine tag, purified hIL-3 with full biological activity was obtained using immobilized metal affinity chromatography, factor Xa protease cleavage, and anion exchange chromatography.     

Helicobacter pylori proteomics by 2‐DE/MS, 1‐DE‐LC/MS and functional data mining

With its predicted proteome of 1550 proteins (data set Etalon) Helicobacter pylori 26695 represents a perfect model system of medium complexity for investigating basic questions in proteomics. We analyzed urea‐solubilized proteins by 2‐DE/MS (data set 2‐DE) and by 1‐DE‐LC/MS (Supprot); proteins insoluble in 9 M urea but solubilized by SDS (Pellet); proteins precipitating in the Sephadex layer at the application side of IEF (Sephadex) by 1‐DE‐LC/MS; and proteins precipitating close to the application side within the IEF gel by LC/MS (Startline). The experimental proteomics data of H. pylori comprising 567 proteins (protein coverage: 36.6%) were stored in the Proteome Database System for Microbial Research ( http://www.mpiib‐berlin.mpg.de/2D‐PAGE/ ), which gives access to raw mass spectra (MALDI‐TOF/TOF) in T2D format, as well as to text files of peak lists. For data mining the protein mapping and comparison tool PROMPT ( http://webclu.bio.wzw.tum.de/prompt/ ) was used. The percentage of proteins with transmembrane regions, relative to all proteins detected, was 0, 0.2, 0, 0.5, 3.8 and 6.3% for 2‐DE, Supprot, Startline, Sephadex, Pellet, and Etalon, respectively. 2‐DE does not separate membrane proteins because they are insoluble in 9 M urea/70 mM DTT and 2% CHAPS. SDS solubilizes a considerable portion of the urea‐insoluble proteins and makes them accessible for separation by SDS‐PAGE and LC. The 2‐DE/MS analysis with urea‐solubilized proteins and the 1‐DE‐LC/MS analysis with the urea‐insoluble protein fraction (Pellet) are complementary procedures in the pursuit of a complete proteome analysis. Access to the PROMPT‐generated diagrams in the Proteome Database allows the mining of experimental data with respect to other functional aspects.     

Expression,Solubilization and Purification of a Human Olfactory Receptor from <Emphasis Type="Italic">Escherichia coli</Emphasis>

Olfactory receptors pertaining to G protein-coupled receptor (GPCR) are integral membrane proteins composed of seven transmembrane spanning domains. It has been reported that these receptor proteins are difficult to overexpress, solubilize, and purify because of their complicated structures and strong hydrophobicity. In this study, full-length human olfactory receptor (hOR) 2AG1 was overexpressed in E. coli as a fusion protein with a glutathione S-transferase (GST) tag mainly as an inclusion body without any mutations or deletions in the gene. This protein was difficult to solubilize with detergents and chaotropic agents, and only N-lauroyl sarcosine was found to be suitable for solubilizing it. In contrast, Trition X-100 was found to solubilize most of the impurity proteins from the insoluble fraction in E. coli. Based on this observation, we applied a simple and efficient column-free method using these two detergents for the purification of the olfactory receptor protein. In this method, the insoluble fraction of the cell lysate was first treated with Triton X-100 to remove impurity proteins. The remaining insoluble fraction was then further treated with N-lauroyl sarcosine to solubilize the olfactory receptor protein. Milligram quantity of the human olfactory receptor was produced. This is the first report to produce full-length of the olfactory receptor from E. coli.     

Cloning, Overexpression and Purification of Bacillus subtilis Elongation Factor Tu in Escherichia coli

To establish the overexpression and one-step purification system of Bacillus subtilis elongation factor-Tu (EF-Tu), the EF-Tu gene was amplified with or without own ribosome binding site (rbs) by PCR and the only PCR product without rbs was subcloned successfully. For the expression of the EF-Tu gene cloned after PCR amplification, a constitutive expression system and inducible expression system with His₆ tag at N-terminus or C-terminus, or glutathione-S-transferase (GST) fusion system were examined in E. coli and B. subtilis. Except GST fusion system in E. coli, however, all other trials were unsuccessful at the step of plasmid construction for the EF-Tu expression. The GST/EF-Tu fusion proteins were highly expressed by IPTG induction and obtained as both soluble and insoluble form. From the soluble GST/EF-Tu fusion protein, EF-Tu was obtained to near homogeneity by one-step purification with glutathione-sepharose affinity column chromatography followed by factor Xa treatment. The purified EF-Tu showed high GDP binding activity. These results indicate that the GST/EF-Tu fusion system is favorable to overexpression and purification of B. subtilis EF-Tu.     

Expression of foreign proteins in<Emphasis Type="Italic"> Escherichia coli</Emphasis> by fusing with an archaeal FK506 binding protein

Improper protein-folding often results in inclusion-body formation in a protein expression system using Escherichia coli. To express such proteins in the soluble fraction of E. coli cytoplasm, we developed an expression system by fusing the target protein with an archaeal FK506 binding protein (FKBP). It has been reported that an archaeal FKBP from a hyperthermophilic archaeon, Thermococcus sp. KS-1 (TcFKBP18), possesses not only peptidyl–prolyl cis–trans isomerase activity, but also chaperone-like activity to enhance the refolding yield of an unfolded protein by suppressing irreversible protein aggregation. To study the effect of this fusion strategy with FKBP on the expression of foreign protein in E. coli, a putative rhodanese (thiosulfate sulfurtransferase) from a hyperthermophilic archaeon and two mouse antibody fragments were used as model target proteins. When they were expressed alone in E. coli, they formed insoluble aggregates. Their genes were designed to be expressed as a fusion protein by connecting them to the C-terminal end of TcFKBP18 with an oligopeptide containing a thrombin cleavage site. By fusing TcFKBP18, the expression of the target protein in the soluble fraction was significantly increased. The percentage of the soluble form in the expressed protein reached 10–28% of the host soluble proteins. After purification and protease digestion of the expressed antibody fragment–TcFKBP18 fusion protein, the cleaved antibody fragment (single-chain Fv) showed specific binding to the antigen in ELISA. This indicated that the expressed antibody fragment properly folded to the active form.     

截短型人胰岛素样生长因子-Ⅰ 在大肠杆菌中的表达、纯化和鉴定

利用PCR、删除突变和基因重组技术构建了N端缺失3个氨基酸的人胰岛素样生长因子-[des(1-3)IGF-]的表达载体pExSec/IGF,在大肠杆菌蛋白酶缺陷株BL21(DE3)中,通过用IPTG于超常规的12℃低温诱导16h,des(1-3)IGF-获得了可溶性表达。表达水平达到可溶性细菌总蛋白约15%。经超滤和SephadexG-50凝胶过滤,des(1-3)IGF-纯度分别达到49%和82%,且表现出明显的免疫学活性和刺激Balb3T3细胞增殖的生物学活性。     

Genes in the insulin and insulin-like growth factor pathway and odds of metachronous colorectal neoplasia

Insulin and insulin-like growth factor (IGF) genes are implicated in colorectal carcinogenesis. Gene-by-gene interactions that influence the insulin/IGF pathways were hypothesized as modifiers of colorectal neoplasia risk. We built a classification tree to detect interactions in 18 IGF and insulin pathway-related genes and metachronous colorectal neoplasia among 1,439 subjects pooled from two chemoprevention trials. The probability of colorectal neoplasia was greatest (71.8%) among carriers of any A allele for rs7166348 (IGF1R) and AA genotype for rs1823023 (PIK3R1). In contrast, carriers of any A at rs7166348 (IGF1R), any G for the PIK3R1 variant, and AA for rs10426094 (INSR) had the lowest probability (14.3%). Logistic regression modeling showed that any A at rs7166348 (IGF1R) with the AA genotype at rs1823023 (PIK3R1) conferred the highest odds of colorectal neoplasia (OR 3.7; 95% CI 2.2–6.5), compared with carriage of GG at rs7166348 (IGF1R). Conversely, any A at rs7166348 (IGFR1), any G allele at rs1823023 (PIK3R1), and the AA genotype at rs10426094 (INSR) conferred the lowest odds (OR 0.22; 95% CI 0.07–0.66). Stratifying the analysis by parent study and intervention arm showed highly consistent trends in direction and magnitude of associations, with preliminary evidence of genotype effects on measured IGF-1 levels in a subgroup of subjects. These results were compared to those from multifactor dimensionality reduction, which identified different single nucleotide polymorphisms in the same genes (INSR and IGF1R) as effect modifiers for colorectal neoplasia. These results support a role for genetic interactions in the insulin/IGF pathway genes in colorectal neoplasia risk.