Heterologous expression and characterization of the endocellulase encoding gene cel3A from the basidiomycete Polyporus arcularius

The genomic and cDNA clones encoding the carboxymethyl cellulase (CMCase) gene (cel3A) of Polyporus arcularius were sequenced and characterized. The coding region of cel3A, composed of 1329 bp, was found to encode a polypeptide of 243 amino acids that has similarity with FI-CMCase of Aspergillus aculeatus. Expression of the cel3A cDNA in Escherichia coli led to production of a nonglycosylated protein as an active form; moreover, CMCase activity measured by the viscometric method was enhanced 4.47 times by addition of cellobiose. These results indicate that glycosylation and any modification of protein such as processing are not required for Cel3A activity.     

Secretive expression of the Aspergillus aculeatus cellulase (FI-CMCase) by Saccharomyces cerevisiae

A cDNA encoding FI-carboxymethylcellulase (FI-CMCase) of the fungus Aspergillus aculeatus was expressed in Saccharomyces cerevisiae under the control of the glyceraldehyde-3-phosphate dehydrogenase gene (GAP) promoter of S. cerevisiae. The transformed cells were able to secrete FI-CMCase efficiently into the culture medium as active enzyme. The recombinant FI-CMCases were observed to be two different enzymes of different molecular mass, one of which corresponded to native FI-CMCase (non-glycosylated FI-CMCase) and the other of which was an N-glycosylated protein (glycosylated FI-CMCase). The recombinant glycosylated FI-CMCase showed a higher thermostability than that of the native enzyme, although the former showed slightly lower activity toward the substrate than the latter.     

Molecular Cloning of a cDNA Encoding Ribosome Inactivating Protein from Amaranthus viridis and Its Expression in E. coli

In order to isolate a cDNA clone of ribosome inactivating protein (RIP), a cDNA library was constructed in Uni-ZAP XL vector with poly(A) RNA purified from leaves of Amaranthus viridis. To get the probe for screening the library, PCR of phage DNA was conducted using the vector primer and degenerate primer designed from a conserved putative active site of the RIPs. Twenty-six cDNA clones from about 600,000 plaques were isolated, and one of these clones was fully sequenced. It was 1,047 bp and contained an open reading frame encoding 270 amino acids. The deduced amino acid sequence had a putative signal sequence of 17 amino acids and a putative active site (AIQMVAEAARFFKYIE) conserved in other RIPs. E. coli cells expressing A. viridis RIP cDNA did not grow well as compared to control cells, indicating that recombinant A. viridis RIP presumably inactivated E. coli ribosomes. In addition, recombinant A. viridis RIP cDNA produced by E. coli had translation inhibition activity in vitro.     

Expression and Purification of Recombinant 3C Proteinase of Coxsackievirus B3

We have cloned various lengths of coxsackievirus B3 cDNA encompassing the region encoding the 3C proteinase, which is essential to the viral replication cycle. Such viral cDNAs were fused in frame to the 5′terminal portion of the lacZ’ gene carried on the vector pUCl18 to express mature 3C proteinase in Escherichia coli. In the E. coli cells containing pCXB108 or pCXB117, constructed for this study, a large amount of 23-kDa protein was synthesized in the presence of IPTG. This protein was purified and was shown to be intact 3C proteinase. These data suggest that 3C proteinase, expressed as a part of a fusion protein, was active in E. coli and released itself from the precursor fusion protein by autocatalytic cleavage.     

AtJ1, a mitochondrial homologue of theEscherichia coli DnaJ protein

The nucleotide sequence of a cDNA clone fromArabidopsis thaliana ecotype Columbia was determined, and the corresponding amino sequence deduced. The open reading frame encodes a protein, AtJ1, of 368 residues with a molecular mass of 41 471 Da and an isoelectric point of 9.2. The predicted sequence contains regions homologous to the J- and cysteine-rich domains ofEscherichia coli DnaJ, but the glycine/phenylalanine-rich region is not present. Based upon Southern analysis,Arabidopsis appears to have a singleatJ1 structural gene. A single species of mRNA, of 1.5 kb, was detected whenArabidopsis poly(A)⁺ RNA was hybridized with theatJ1 cDNA. The function ofatJ1 was tested by complementation of adnaJ deletion mutant ofE. coli, allowing growth in minimal medium at 44°C. The AtJ1 protein was expressed inE. coli as a fusion with the maltose binding protein. This fusion protein was purified by amylose affinity chromatography, then cleaved by digestion with the activated factor X protease. The recombinant AtJ1 protein was purified to electrophoretic homogeneity.In vitro, recombinant AtJ1 stimulated the ATPase activity of bothE. coli DnaK and maize endosperm cytoplasmic Stress70. The deduced amino acid sequence of AtJ1 contains a potential mitochondrial targeting sequence at the N-terminus. Radioactive recombinant AtJ1 was synthesized inE. coli and purified. When the labeled protein was incubated with intact pea cotyledon mitochondria, it was imported and proteolytically processed in a reaction that depended upon an energized mitochondrial membrane.Abbreviations MBP maltose binding protein - PCR polymerase chain reaction - Stress70c the cytosolic member of the 70 kDA family of stress-related proteins     

乌桕SsSAD基因的原核表达与纯化研究

乌桕是一种重要的木本油料树种。SAD(stearoyl-acyl ACP desaturase)是油料植物中将饱和脂肪酸转变成不饱和脂肪酸的一种关键脱氢酶。为了进一步揭示乌桕SsSAD的功能,该研究在大肠杆菌中表达了该蛋白。结果表明:(1)通过RT-PCR的方法从乌桕种子中克隆出了SsSAD基因编码区全长序列,并将其克隆到低温诱导的原核表达载体pCold TF上,构建原核重组表达载体pCold TF/SsSAD,转化大肠杆菌BL 21star(DE3)并获得原核表达工程菌株。(2)通过IPTG法低温诱导表达融合蛋白。该重组质粒在大肠杆菌中得到了高效表达,融合蛋白分子质量约为101kD,且在上清液和包涵体中均有表达,可溶性部分经亲和层析纯化和Western blotting检测证实获得了重组蛋白,上述结果为进一步研究乌桕SsSAD的结构和功能奠定了基础。     

Purification and Some Properties of Urethane Hydrolase II from Lactobacillus casei ω ATCC 7469

The β-1,3-glucanase (1,3-β-d-glucan glucanohydrolase, EC 3.2.1.6) gene from Flavobacterium dormitator var. glucanolyticae was cloned into Escherichia coli C600 with a vector plasmid, pBR322. The E. coli cells carrying a recombinant plasmid, pKUβG1 (8.2 kb), showed a high β-1,3-glucanase activity and a lytic activity on viable yeast cells. These activities were found in the peripiasmic space of E. coli clone cells. Southern hybridization analysis showed that the cloned gene was derived from F. dormitator chromosomal DNA. The gene products were purified from the periplasmic fraction of E. coli by ammonium sulfate fractionation and ion-exchange chromatography. The purified enzymes were demonstrated to be identical with a lytic endo-β-1,3-glucanase II and a nonlytic endo-β-1,3-glucanase I from F. dormitator from their enzymological and immunological properties. In the E. coli cells, endo-β-1,3-glucanase I was also formed by a proteolytic digestion of endo-β-1,3-glucanase II during the cultivation as in F. dormitator. Thus, the only endo-β-1,3-glucanase II was coded for in the cloned gene.     

Purification and characterization of pea thioredoxin f expressed in Escherichia coli

The recently cloned cDNA for pea chloroplast thioredoxin f was used to produce, by PCR, a fragment coding for a protein lacking the transit peptide. This cDNA fragment was subcloned into a pET expression vector and used to transform E. coli cells. After induction with IPTG the transformed cells produce the protein, mainly in the soluble fraction of the broken cells. The recombinant thioredoxin f has been purified and used to raise antibodies and analysed for activity. The antibodies appear to be specific towards thioredoxin f and do not recognize other types of thioredoxin. The recombinant protein could activate two chloroplastic enzymes, namely NADP-dependent malate dehydrogenase (NADP-MDH) and fructose 1,6-bisphosphatase (FBPase), both using dithiothreitol as a chemical reductant and in a light-reconstituted/thylakoid assay. Recombinant pea thioredoxin f turned out to be an excellent catalyst for NADP-MDH activation, being the more efficient than a recombinant m-type thioredoxin of Chlamydomonas reinhardtii and the thioredoxin of E. coli. At the concentrations of thioredoxin used in the target enzyme activation assays only the recombinant thioredoxin f activated the FBPase.     

<Emphasis Type="Italic">Escherichia coli</Emphasis> topoisomerase I is an iron and zinc binding protein

Escherichia coli topoisomerase I (TopA) cleaves and rejoins one strand of double-stranded DNA to relax the negatively supercoiled DNA. Structurally, TopA contains an N-terminal catalytic fragment and a C-terminal zinc-binding region that is required for relaxation of the negatively supercoiled DNA. Here we report that E. coli TopA is an iron and zinc binding protein. The UV–Vis absorption measurements and metal content analyses reveal that TopA purified from E. coli cells grown in the rich LB medium contains both iron and zinc. However, TopA purified from E. coli cells grown in the M9 minimal medium has negligible amounts of zinc or iron and no topoisomerase activity. Nevertheless, supplement of exogenous zinc or iron in E. coli cells grown in the M9 minimal medium produces the zinc- or iron-bound TopA, respectively. Whereas the zinc-bound TopA is fully active to relax the negatively supercoiled DNA, the iron-bound TopA has little or no enzyme activity. Furthermore, excess iron in the M9 minimal medium is able to compete with the zinc binding in TopA in E. coli cells and attenuate the topoisomerase activity, suggesting that E. coli TopA may be modulated by iron and zinc binding in vivo.     

Overproduction and single-step purification of Bacillus stearothermophilus peroxidase in Escherichia coli

Summary The cloned peroxidase gene from Bacillus stearothermophilus was highly expressed in Escherichia coli. Using the high copy number plasmid which is temperature-sensitive and its own strong promoter, this thermostable peroxidase was produced at 28% of the total cell proteins when the cells were grown at 42°C. The enzyme could be easily purified from E. coli by heat treatment and single-column Sephadex G-200 chromatography. From a 200 ml culture, 30 mg of purified enzyme was obtained. The peroxidase produced by E. coli showed a thermostability, haem type and content identical with those of the peroxidase produced by B. stearothermophilus.Offprint requests to: H. Okada     

Analysis of a cDNA encoding arginine decarboxylase from oat reveals similarity to the Escherichia coli arginine decarboxylase and evidence of protein processing

Summary Arginine decarboxylase is the first enzyme in one of the two pathways of putrescine synthesis in plants. We purified arginine decarboxylase from oat leaves, obtained N-terminal amino acid sequence, and then used this information to isolate a cDNA encoding oat arginine decarboxylase. Comparison of the derived amino acid sequence with that of the arginine decarboxylase gene from Escherichia coli reveals several regions of sequence similarity which may play a role in enzyme function. The open reading frame (ORF) in the oat cDNA encodes a 66 kDa protein, but the arginine decarboxylase polypeptide that we purified has an apparent molecular weight of 24 kDa and is encoded in the carboxyl-terminal region of the ORF. A portion of the cDNA encoding this region was expressed in E. coli, and a polyclonal antibody was developed against the expressed polypeptide. The antibody detects 34 kDa and 24 kDa polypeptides on Western blots of oat leaf samples. Maturation of arginine decarboxylase in oats appears to include processing of a precursor protein.     

Overexpression of alginate lyase of <Emphasis Type="Italic">Pseudoalteromonas elyakovii</Emphasis> in <Emphasis Type="Italic">Escherichia coli</Emphasis>, purification,and characterization of the recombinant alginate lyase

The alyPEEC gene encoding alginate lyase from marine bacterium Pseudoalteromonas elyakovii IAM 14594 was subcloned into pBAD24 with arabinose promoter and sequenced, and overexpressed in TOP10 strain of E. coli after arabinose induction. Expression levels of alyPEEC gene in E. coli cells were over 39.6-fold higher than those in P. elyakovii IAM 14594 cells. The molecular mass of purified alginate lyase from the engineered E. coli cells was estimated to be 32.0 kDa. Optimum pH and temperature of the alginate lyase activity were 7.0 and 30 °C, respectively. The enzyme was unstable on heating and in acidic and alkaline solution. The enzyme activity was stimulated by the MgCl₂, NaCl, KCl, CaCl₂, BaCl₂ and MnCl₂, but was inhibited by the addition of 1.0 mM of EGTA, EDTA, SDS, ZnSO₄, AgNO₃, and CoCl₂. All the alginate, polyM and polyG could be converted into oligosaccharides with more than tetrasaccharides by the purified recombinant alginate lyase, suggesting that the recombinant alginate lyase produced by the engineered E. coli has highly potential application in seaweed genetics, food and pharmaceutical industries.     

Overexpression, purification, and functional characterization of the group II chaperonin from the hyperthermophilic archaeum Pyrococcus horikoshii OT3

Overexpression in Escherichia coli and functional characterization of the group II chaperonin from the hyperthermophilic archaeum Pyrococcus horikoshii OT3 were investigated in this study. PhCpn, the chaperonin gene from the P. horikoshii OT3, was amplified by PCR from the P. horikoshii genomic DNA, subcloned into pET21a vector, and expressed in three E. coli host cells such as BL21, Rosetta, and Codonplus (DE3). Among these host cells, E. coli Rosetta showed the highest expression level of recombinant PhCpn at induction with 1 mM IPTG. The recombinant PhCpn was purified to 91% by heat-shock treatment and anion-exchange chromatography. The ATPase activity of the purified PhCpn increased in a PhCpn concentration-dependent manner. Also, PhCpn protected the inorganic phosphatase from thermal inactivation at 85 and 110°C, speculating that PhCpn is effective in in vitro holding of the protein. The holding efficiency was enhanced by the addition of Mg²⁺ ion. Through the coexpression of pro-carboxypeptidase B (pro-CPB) and PhCpn in E. coli Rosetta, pro-CPB was produced as a soluble and active form with a marked yield. This result indicated that PhCpn facilitated the in vivo correct folding of pro-CPB and could be used as powerful and novel molecular machinery for the production of recombinant proteins as soluble and active forms in E. coli.     

Cloning,sequence analysis and expression of a cDNA encoding active phosphoenolpyruvate carboxylase of the C3 plant Solanum tuberosum

A cDNA coding for phosphoenolpyruvate carboxylase (PEPC) was isolated from a cDNA library from Solanum tuberosum and the sequence of the cDNA was determined. It was inserted into a bacterial expression vector and a PEPC^- Escherichia coli mutant could be complemented by the cDNA construct. A functional fusion protein could be synthesized in E. coli. The properties of this PEPC protein clearly resembled those of typical C3 plant enzymes.     

Expression of HSV-1 ICP0 antigen peptide in prokaryotic cells and preparation of specific antibody

As an immediate-early protein of herpes simplex virus, infected-cell polypeptide 0 (ICP0) exhibits complicated interactions with host cells, and its regulatory function on gene expression is of great importance. Since the ICP0 encoding sequence contains many rare codons which are absent in E.coli, and ICP0 is highly unstable in prokaryotic cells, expression of entire ICP0 in prokaryotic cells has never been reported. In order to further investigate the function of ICP0, a recombinant plasmid was constructed by subcloning a cDNA fragment encoding an amino-terminal of 105 residues of the ICP0 protein into pGEX-5x-1 vector. The resulting GST-105 fusion antigen peptide was expressed with high efficiency in E.coli. Antibodies prepared after the immunization of mice with purified fusion protein can recognize not only the denatured ICP0 protein, but also the native ICP0 protein with normal biological conformation. Foundation items: National natural science foundation items (30570081 and 30670094)     

鲑鱼生长激素基因分泌型表达质粒的构建

生长激素(GH)是动物垂体前叶分泌的一种多肽类激素.应用分子重组及PCR等技术,构建了一种鲑鱼生长激素基因分泌型表达质粒pOsGH153,使编码鲑鱼生长激素成熟肽的序列克隆在大肠杆菌分泌型表达载体PIN-Ⅲ-ompA内,直接位于编码大肠杆菌外膜蛋白A信号肽序列的下游,在Lpp-Lac杂合启动子控制下,经IPTG诱导,分子量约23 000的鲑鱼生长激素在大肠杆菌中获得高效表达,该产物具有天然鲑鱼生长激素的免疫活性,直接分泌到细胞周质,而信号肽被自动剪除.     

Molecular chaperone activity of tomato (<Emphasis Type="Italic">Lycopersicon esculentum</Emphasis>) endoplasmic reticulum-located small heat shock protein

The gene encoding the small heat shock protein (sHSP), LeHSP21.5, has been previously cloned from tomato (GenBank accession no. AB026983). The deduced amino acid sequence of this tomato sHSP was most similar to that of other endoplasmic reticulum (ER)-localized sHSPs (ER-sHSP) and can be predicted to target the ER. We examined whether the gene product of LeHSP21.5 (probable ER-sHSP) can act as molecular chaperone. For functional analysis, LeHSP21.5 protein was expressed in Escherichia coli as His₆-tagged protein in the C-terminal and purified. We confirmed that ER-sHSP could provide thermal protection of soluble proteins in vitro. We compared the thermal stability of E. coli strain BL21 (DE3) transformed with pET-ER-sHSP with the control E. coli strain BL21(DE3) transformed with only the pET vector under heat shock and IPTG-induced conditions. Most of the protein extracts from E. coli cells expressing ER-sHSP were protected from heat-induced denaturation, whereas extracts from cells not expressing ER-sHSP were very heat-sensitive under these conditions. A similar protective effect was observed when purified ER-sHSP was added to an E. coli cell extract. ER-sHSP prevented the thermal aggregation and inactivation of citrate synthase. These collective findings indicate that ER-sHSP can function as a molecular chaperone in vitro. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Expression of a Recombinant Molt-Inhibiting Hormone of the Kuruma Prawn Penaeus japonicus in Escherichia coli

The crustacean molt-inhibiting hormone (MIH) suppresses ecdysteroid synthesis by the Y-organ. The MIH of the kuruma prawn Penaeus japonicus has recently been isolated and its cDNA cloned. In this study, we expressed the MIH in Escherichia coli to obtain a large quantity of this hormone with biological activity. The MIH cDNA was processed and ligated into an expression plasmid. E. coli was transformed with this plasmid, and then the recombinant MIH (r-MIH) was expressed. The r-MIH was put through the refolding reaction and was purified by reverse-phase HPLC. N-terminal amino acid sequence and time-of-flight mass spectral analyses supported the idea that the r-MIH had the entire sequence. By in vitro bioassay using the Y-organ of the crayfish, the r-MIH was found to be comparable to natural MIH in inhibiting ecdysteroid synthesis.     

Design,expression and characterization of recombinant hybrid peptide Attacin-Thanatin in <Emphasis Type="Italic">Escherichia coli</Emphasis>

Antimicrobial peptides will be attractive and potential candidates as peptide drugs because of their efficient action against microbes and low toxicity to mammal cells. To improve their antibacterial activity, some modifications needs to be made. In this research, the hybrid peptide gene Attacin-Thanatin with 642 bp in length with preferred codons of E. coli was generated using the technology of Gene splicing by overlap extension. The gene was inserted in-frame into E. coli expression plasmid pET-32a (+) and induced to express in E. coli Rosetta. The recombinant protein was partial purified and its biological activity was determined. Analysis of the E. coli Rosetta induced with IPTG revealed that the molecular weight of fusion protein was approximately 41.8 kDa, which perfectly matched the mass calculated from the amino acid sequence. Biological activity detection showed that this peptide effectively inhibited the growth of the test bacteria including E. coli DH5α, E. coli BL21 (DE3), Salmonella choleraesuis and Staphylococcus aureus. Among these bacteria, the Gram-negative E. coli was the most sensitive. Furthermore, there was minor hemolysis activity for porcine red blood cells. So, the results indicated that the hybrid peptide Attacin-Thanatin could be served as a promising candidate for the chemical antibiotics.