Characterization of a recombinant mu-class glutathione S-transferase from Taenia solium

A Taenia solium larval glutathione S-transferase fraction (SGSTF), composed of two proteins with Mr 25,500 (SGSTM1) and 26,500 (SGSTM2), was purified by GSH-sepharose. Its N-terminal sequence analysis revealed that both proteins are related to mammalian mu-class GST enzymes. A cDNA clone coding for SGSTM1 was isolated and the amino acid sequence analysis showed close identity with two Echinococcus GSTs and also high identity with several mu-class GSTs that have been reported. In addition, SGSTM1 presents a similar structure to mu-class GSTs, including the mu loop. The recombinant SGSTM1 is a dimeric protein with enzymatic properties clearly related to mammalian mu-class GSTs. Western blot studies indicated that SGSTM1 is not antigenically related to SGSTM2 or mammalian GSTs from rabbit, pig and rat livers. Immunization with SGSTF and SGSTM2 was highly effective in reducing cysticerci load in murine cysticercosis. In contrast, no protection was obtained using native SGSTM1 and recombinant SGSTM1 as immunogens.     

Molecular cloning and enzymatic characterization of a class mu glutathione <Emphasis Type="Italic">S</Emphasis>-transferase of <Emphasis Type="Italic">Paragonimus westermani</Emphasis>

Glutathione S-transferase (GST) is a component of a second line of defense against bioreactive radicals derived from host immune attack. Paragonimus westermani causes acute or chronic lung diseases in mammals. A cDNA clone, PwGST#11, of adult P. westermani produced in the present study was 748 bp long and encoded an open reading frame of 217 amino acids with a starting methionine. The molecular mass of this putative polypeptide, Pw26GST, was estimated to be 25.1 kDa with an isoelectric point of 5.7. Pw26GST was homologous with the 26-kDa GSTs of trematodes and vertebrates. Nine of the ten amino acid residues lining the glutathione-binding pocket were conserved. Putative Pw26GST polypeptide was clustered with 26-kDa GSTs of trematodes belonging to the class mu. Recombinant Pw26GST protein generated bacterially, revealed GST enzyme activity toward an universal and class mu-specific substrates. Mouse antisera to recombinant Pw26GST protein recognized native 26-kDa GST of P. westermani but not the GSTs of any other trematodes. Collectively, Pw26GST was found to be a member of class mu GSTs of P. westermani.     

Molecular cloning and characterization of a new Japanese cedar pollen allergen homologous to plant isoflavone reductase family

BACKGROUND: Japanese cedar (Cryptomeria japonica) pollen is a major cause of seasonal pollinosis, and more than 10% of Japanese people suffer from this allergic disorder. However, only two major pollen allergens, Cry j 1 and Cry j 2, have been identified and exclusively characterized. OBJECTIVE: The aim of this study was to explore and identify important Japanese cedar pollen allergens other than Cry j 1 or Cry j 2. METHODS: C. japonica cDNA library was immunoscreened by rabbit antiserum raised against a partially purified cedar pollen allergen fraction. An isolated cDNA clone was inserted into a glutathione S-transferase (GST)-tagged Escherichia coli expression vector to obtain recombinant GST fusion protein. Non-fusion recombinant protein was purified by glutathione Sepharose affinity chromatography in conjunction with factor Xa cleavage of the GST moiety. IgE-binding ability of the recombinant protein was then evaluated by western blot analysis and enzyme-linked immunosorbent assay (ELISA). RESULTS: The cDNA encodes 306 amino acids with significant sequence similarity to those of plant isoflavone reductase-like proteins, which include a recently identified birch pollen allergen Bet v 5. Western blot analysis demonstrated that recombinant protein was recognized by cedar pollinosis patient IgE. In contrast to Bet v 5 being reported as a minor allergen, the recombinant protein exhibited 76% IgE binding frequency (19/25) against pollinosis patients. CONCLUSION: Here we identified the third member of Japanese cedar pollen allergen homologous to isoflavone reductase. Its high IgE-binding frequency implicates that the isoflavone reductase homologue might be an additional major pollen allergen in C. japonica.     

A novel type of glutathione S-transferase in Onchocerca volvulus.

Onchocerca volvulus is a pathogenic human filarial parasite which, like other helminth parasites, is capable of evading the host's immune responses by a variety of defense mechanisms which are likely to include the detoxification and repair mechanisms of the enzyme glutathione S-transferase (GST). In this study, we show that one of the previously described GSTs from O. volvulus appears to possess the characteristics of a secreted enzyme. When the complete O. volvulus GST1 (OvGST1) sequence presented here is compared with those of other GSTs, 50 additional residues at the N terminus are observed, the first 25 showing characteristics of a signal peptide. This is consistent with the N-terminal sequence data on the native mature enzyme which begins at amino acid 26, based on the deduced protein sequence from the cDNA. The native protein, without the signal peptide sequence, possesses a 24-amino-acid extension not present in other GSTs. The deduced amino acid sequence of the OvGST1 cDNA clone was shown to possess four potential N-glycosylation sites. Digestion of O. volvulus homogenate with endoglycosidase, followed by detection of OvGST1 with specific antibody, indicated that the enzyme possesses at least two N-linked oligosaccharide chains. Gel filtration of the Escherichia coli-produced recombinant OvGST1 showed that it is enzymatically active as a nonglycosylated dimer. OvGST1 is found in the media surrounding adult worms maintained in culture, indicating that, in vitro, this enzyme is released from the worm. The strongest immunostaining for OvGST1 was observed in the outer cellular covering of the adult worm body, the syncytial hypodermis, especially in the interchordal hypodermis, where the peripheral membrane forms a series of lamellae which run into the outer zone of the hypodermal cytoplasm.     

<Emphasis Type="Italic">Clonorchis sinensis</Emphasis>: molecular cloning and functional expression of a novel cytosolic glutathione transferase

Glutathione transferases (GSTs) represent a large family of enzymes. In the high throughput sequencing of the cDNA library constructed from the adult stage of Clonorchis sinensis (Cs), we isolate another cDNA clone encoding a novel cytosolic GST enzyme. To discriminate with our former reported CsGST, we designated this GST as CsGST1. This new cDNA contains 744 bp with a putative open reading frame of 213 amino acids. The deduced amino acid sequence exhibits 88% identity to Opisthorchis viverrini 28GST (Ov28GST), 60 and 52% identity to C. sinensis cytosolic 28-kDa GST (Cs28GST) and CsGST, respectively. The CsGST1 was expressed in Escherichia coli BL21(DE3) as a His-tag fusion protein and was purified by Ni-NTA agarose. The recombinant CsGST1 showed moderate GST activity of 0.79 U mg⁻¹. The average K _m of the CsGST1 for 1-chloro-2, 4-dinitrobenzene is 150 μM. Cibacron blue F3GA and albendazole inhibited the CsGST1 activity with average IC₅₀ values of 9.1 and 265.4 μM, respectively. The nucleotide sequence reported in this paper was submitted to the GenBank Database with accession number DQ342327.     

华支睾吸虫卵黄前体蛋白B基因的识别、序列分析和克隆表达

为识别和克隆华支睾吸虫新基因 ,对华支睾cDNA质粒文库进行随机筛选并测序 ,并利用在线生物信息学工具进行序列分析 ,识别华支睾吸虫未知基因 ,同时根据PGEX -4T- 1多克隆位点及未知基因的序列设计引物 ,PCR扩增目的基因 ,并构建原核重组质粒。结果发现了CsvpB基因 ,其完整阅读框含 76 2个碱基 ,编码 2 5 4个氨基酸 ,理论分子量为 2 7. 7kDa。序列分析表明 ,CsvpB蛋白与其它物种的卵黄前体蛋白有较高的同源性 ,所构建的重组原核表达质粒PGEX- 4T- 1 vpB经PCR、双酶切及测序证实与目标基因相符。     

Molecular cloning and characterization of cDNA encoding a novel cytosolic glutathione transferase from Clonorchis sinensis

Glutathione transferases (GSTs) are a group of multifunction isoenzymes coded by many genes. A cDNA encoding a novel cytosolic GST enzyme was cloned from a Clonorchis sinensis (Cs) adult worm cDNA library by large-scale sequencing. This new cDNA contains 786 bp with a putative open reading frame of 212 amino acids. The deduced amino acid sequence exhibits 61% identity to C. sinensis cytosolic 28-kDa GST. Recombinant CsGST was overexpressed in Escherichia coli BL21(DE3) and was purified by Ni–NTA Agarose. Enzymatic assays showed that the recombinant CsGST had a high activity of 22.7 U mg⁻¹. The average K _m of the CsGST for 1-chloro-2,4-dinitrobenzene is 111 μM. Cibacron blue F3GA and albendazole inhibited the CsGST activity with respective average IC₅₀ of 1.1 and 247.1 μM. It provides a model for the structure and physiological function analysis on CsGST. The nucleotide sequence reported in this paper has been submitted to the GenBank Database with accession number DQ179264.     

Recognition and characterization of TGF-β receptor interacting protein 1 (TRIP-1) containing WD40 repeats from <Emphasis Type="Italic">Clonorchis sinensis</Emphasis> by bioinformatics,cloning, and expression in <Emphasis Type="Italic">Escherichia coli</Emphasis>

A cDNA clone encoding a homologue of transforming growth factor beta (TGF-beta) receptor interacting protein 1 (TRIP-1) was recognized and isolated from full-length cDNA plasmid library of Clonorchis sinensis adult. TRIP-1 is a bifunctional molecule in all eukaryote, which modulates the signaling pathway of TGF-beta as a phosphorylation substrate of TGF-beta type II receptor kinase and controls ribosome assembly and mRNA translation as p36 subunit of the eukaryotic translation initiation factor 3. The structural and immunological characteristics of TRIP-1 from C. sinensis (CsTRIP-1) were analyzed by bioinformatics. The complete coding sequence was expressed in Escherichia coli, and the purified recombinant product was obtained. Western blotting with mixed sera from clonorchiasis patients was positive, whereas the normal was negative, suggesting it is a candidate of diagnostic antigen for clonorchiasis. CsTRIP-1 will aid to explore interaction between host and the parasite as well as the mechanism by which TGF-beta controls the development of C. sinensis and participates in the pathogenesis.     

Recombinant glutathione-S-transferase a major allergen from Alternaria alternata for clinical use in allergy patients

Recombinant proteins are used for vaccines, therapy and diagnosis of many diseases. Biological activity of these may differ from native counterpart and needs investigation. The present study aimed to compare recombinant (r) and native (n) glutathione-S-transferase (GST) from Alternaria alternata. Glutathione-S-transferase sequence showed an ORF of 696bp encoding 26-kDa protein with N-terminus conserved domain. Secondary structure of both forms was comparable with melting temperature of 57 and 59 degrees C, respectively. rGST and nGST showed similar enzymatic activity, allergenicity and potency by ELISA inhibition. Histamine release was comparable in 14/17 patients for both the GSTs. rGST and nGST induced proliferation in PBMC at different concentration. Cell supernatant revealed higher IL-4 and IL-5 levels with low levels of IFN-gamma. In summary, recombinant and native GST demonstrated similar physio-chemical, biological and immunological properties and induced comparable cell mediated and humoral response to be used for diagnosis and specific immunotherapy for the fungal allergy cases.     

Cloning, characterization, and expression of a 200-kilodalton diagnostic antigen of Babesia bigemina

Current serological tests for Babesia bigemina use semipurified merozoite antigens derived from infected erythrocytes. One of the major drawbacks of these tests is that antigen quality can vary from batch to batch. Since the quality of the antigen contributes to the sensitivity and specificity of serological tests, the use of standardized recombinant antigens should ensure consistency in assay quality. Previously, a 200-kDa merozoite antigen (p200) was identified as a candidate diagnostic antigen for use in a serological assay for the detection of B. bigemina antibodies in infected cattle. In this study, we have cloned, characterized, and expressed p200. A 3.5-kbp cDNA clone encoding p200 was isolated and shown to be almost full length, lacking approximately 300 bp at the 5' end. The predicted amino acid sequence shows that p200 consists of a long, highly charged central repeat region of an uninterrupted alpha helix, indicative of a fibrous protein. Immunoelectron microscopy localized p200 to the merozoite cytoplasm, suggesting that the antigen may be a structural protein involved in forming filament structures within the cytoskeleton. The 3.5-kbp cDNA was expressed in bacteria as a fusion protein with glutathione S-transferase (GST), but the yield was poor. To improve the yield, cDNA fragments encoding antigenic domains of p200 were expressed as fusions with GST. One of these fusion proteins, C1A-GST, is composed of a 7-kDa fragment of the p200 repeat region and contains epitopes that react strongly with sera from cattle experimentally infected with B. bigemina. Recombinant C1A-GST should permit the development of an improved enzyme-linked immunosorbent assay for the detection of antibodies against B. bigemina.     

Screening and characterization of variant Theta-class glutathione transferases catalyzing the activation of ethylene dibromide to a mutagen

Ethylene dibromide (EDB) is a widespread environmental pollutant and mutagen/carcinogen. Certain Theta-class glutathione transferases (GSTs), enzymes that catalyze the reaction of reduced glutathione (GSH) with electrophiles, activate EDB to a mutagen. Previous studies have shown that human GST T1-1, but not rat GST T2-2, activates EDB. We have constructed an E. coli lacZ reversion mutagenicity assay system in which expression of recombinant GST supports activation of EDB to a mutagen. Hexa-histidine N-terminal tagging of GST T1-1 results in greatly enhanced expression of the recombinant enzyme and gives a lacZ strain that shows a mutagenic response to EDB at extremely low levels (approximately 1 ng EDB per plate). The hexa-histidine-tagged enzyme was purified in one step by Ni(2+)-affinity chromatography. We applied the lacZ mutagenicity assay to the rapid screening of a library of variant GST Theta enzymes. Sequence variants with altered catalytic activities were identified, purified, and characterized.     

人神经系统特异表达RNA结合蛋白HuC cDNA的克隆、表达及纯化

目的克隆人神经系统表达RNA结合蛋白HuC的cDNA并原核表达纯化。方法提取人神经母细胞瘤SHSY5Y细胞株总RNA,经RT-PCR扩增得到人HuC全长cDNA的克隆。将HuC cDNA克隆到原核表达载体pGEX4T-3载体中,并转化到大肠杆菌中,在获得高效表达后,利用GST纯化系统,对HuC重组蛋白进行纯化。结果经过表达及纯化条件的摸索,最终获得重组HuC蛋白。结论HuC蛋白是一种神经系统表达RNA结合蛋白,重组HuC蛋白的获得为HuC抗体的制备及进一步研究该蛋白的功能奠定了基础。     

Molecular expression of a cysteine proteinase of Clonorchis sinensis and its application to an enzyme-linked immunosorbent assay for immunodiagnosis of clonorchiasis

We produced a recombinant cysteine proteinase of Clonorchis sinensis and tested its value as an antigen for serologic diagnosis of C. sinensis infections. The predicted amino acid sequence of the cysteine proteinase of C. sinensis was 58, 48, and 40% identical to those of cathepsin L cysteine proteinases from Paragonimus westermani, Schistosoma japonicum, and Fasciola hepatica, respectively. Western blotting analysis showed that sera from patients infected with C. sinensis strongly reacted with the recombinant protein and that sera from patients infected with S. japonicum weakly reacted with the recombinant protein. Antibody against the recombinant protein stained proteins migrating at about 37 and 28 kDa in C. sinensis adult worm crude extracts. Immunostaining revealed that the cysteine proteinase of C. sinensis was located in the intestinal epithelial cells of the adult parasite and in intrauterine eggs. The specificity and sensitivity of the recombinant antigen or C. sinensis adult worm crude extracts were assessed by an enzyme-linked immunosorbent assay (ELISA) using serum samples from humans infected with different parasites, including 50 patients with clonorchiasis, and negative controls. The sensitivities of the ELISA with the recombinant antigen and C. sinensis adult worm crude extracts were 96 and 88%, respectively. The specificities of the ELISA with the recombinant antigen and C. sinensis adult worm crude extracts were 96.2 and 100%, respectively. The results suggested that the recombinant cysteine proteinase-based ELISA could provide a highly sensitive and specific assay for diagnosis of clonorchiasis.     

Molecular cloning and immunological characterization of phosphoglycerate kinase from Clonorchis sinensis

The parasite Clonorchis sinensis was determined to utilize a large amount of external glucose to carry its energy metabolism. Phosphoglycerate kinase (PGK), a glycolytic enzyme, found in many parasites, has been identified as one of the candidate molecules distinguished from human counterparts for vaccine and drug developments. A cDNA clone purified by screening a C. sinensis cDNA library using a heterologous cDNA probe encoded a putative peptide of 415 amino acids with over 60% identities with PGKs from a number of animals. The putative peptides revealed domains corresponding to 12 beta-sheets and inner loops forming a substrate-binding cleft of animal PGKs. The gene product was overexpressed in Escherichia coli and showed a PGK-like enzyme activity. A polyclonal antibody raised against the recombinant C. sinensis PGK was specific to native C. sinensis PGK and localized it to the muscular tissue and tegument of the adult flukes. The C. sinensis PGK elicited antibodies in C. sinensis-infected rabbits. Therefore, it is proposed that C. sinensis PGK could be used as an immunoreagent in the serodiagnosis for clonorchiasis.     

Molecular cloning and immunolocalization of the 17 kDa myoglobin of Clonorchis sinensis

We purified the 17 kDa protein abundant in Clonorchis sinensis crude extracts. The N-terminal amino acid sequence of this protein was determined and an oligonucleotide probe synthesized. Using this probe, the cDNA encoding the protein was cloned and sequenced from the C. sinensis cDNA library. It was found to consist of a total of 150 amino acids and to have 41% conserved homology with the myoglobin of the trematodes Paramphistomum epiclitum and Isoparorchis hypselobagri. The gene product over-expressed in the bacterial system was purified and identified as the same molecule in the adult worms. BALB/c mouse sera raised against the adult 17 kDa protein revealed that this myoglobin was distributed throughout the parenchymal tissues except for the eggs and reproductive organs and that the protein may be involved in the survival of C. sinensis in the oxygen-depleted environment of the host.     

华支睾吸虫膜抗原/排泄分泌抗原酸性磷酸酶的克隆、表达、生物学特征分析及组织定位

 目的:对华支睾吸虫(Clonorchis sinensis, Cs)成虫酸性磷酸酶 (acid phosphatase, AP)进行克隆、表达、生物学特征分析、组织定位及膜抗原/排泄分泌抗原鉴定。方法:对CsAP进行生物信息学、分子生物学、免疫组化及明胶酶谱分析。结果:从Cs cDNA文库中筛选出编码AP新基因,全长1 410 bp,重组并由大肠杆菌表达、纯化,得到分子量为55 kD的重组蛋白CsAP。Western blotting分析表明,CsAP既是膜抗原又是分泌排泄抗原;免疫组化显示,CsAP荧光显示于成虫的表皮层和肠支,在囊蚴也有显示,在雷蚴和尾蚴未显示荧光;ELISA分析表明CsAP识别华支睾吸虫病人和日本血吸虫病人存在吸虫间的交叉免疫反应,CsAP及粗抗原识别轻、中、重度感染程度华支睾吸虫病人的差别不明显。重组蛋白免疫大鼠后,总IgG抗体滴度于3周达较高峰,抗体效价大于1∶25 600。明胶降解实验表明：CsAP具降解胶原能力。结论: 上述结果表明,CsAP在大肠杆菌中高效表达,具有较好的免疫原性,但血清诊断价值不理想;CsAP可能既是膜抗原,又是排泄分泌抗原。     

Comparison of the cloned genes of the 26- and 28-kilodalton glutathione S-transferases of Schistosoma japonicum and Schistosoma mansoni.

Both Schistosoma japonicum and S. mansoni contain 28- and 26-kDa glutathione S-transferases (GSTs). Despite their immunological cross-reactivity using rabbit antisera, the S. japonicum 28-kDa GST (Sj28) is weakly immunogenic relative to the S. mansoni protein (Sm28) in mouse immunization experiments using GSTs purified from adult worms. The difference in immunogenicity is also observed during schistosome infection in mice. Using surface-labeled living S. japonicum worms, evidence was obtained for a surface location of Sj28 comparable to that reported for the S. mansoni molecule. The nucleotide and deduced amino acid sequences of cDNA clones corresponding to Sj28 and Sm28 were compared. Despite obvious homology (77% identity), differences were found in regions known to contain T epitopes in the S. mansoni protein which may be an explanation for the striking differences in immunogenicity in regard to antibody production in mice. The 26-kDa GSTs of these two parasites (Sj26 and Sm26) are also closely related on the basis of nucleotide and deduced amino acid sequences, there being 82% identity in the putative coding regions. When the amino acid sequences of Sj28 and Sm28 were compared with those of Sj26 and Sm26, the overall sequence identity was approximately 20%. However, a relatively conserved region was identified in otherwise structurally different molecules which may participate in common properties of these enzymes.