Chemical denaturants induced folding unfolding pathway of the recombinant zebrafish dihydrofolate reductase

Denaturation of proteins plays a crucial part in cellular activities. In this study, we have investigated the folding unfolding pathways of zebrafish dihydrofolate reductase (zDHFR) in presence of different chemical denaturants which were found to be an influential factor for the refolding yield by UV-visible spectrophotometric analysis. The activity change of zDHFR has been observed in presence of three different denaturants like Acetic Acid (AcOH), Sodium Dodecyl Sulphate (SDS), and Ethanol (C2H5OH). Spectrophotometric analysis reveals that protein unfolded completely at different concentrations and times by these denaturants. The spontaneous refolding experiments of chemically denatured zDHFR were also conducted to verify the spontaneous refolding yield. These investigations have helped us to decipher a picture about the denaturants contributing to achieving the refolding yield. We observed that acetic acid is a stronger denaturant among all, and the spontaneous refolding yields were higher from SDS denaturation. In the light of the above findings, higher spontaneous refolding yields were obtained from the low concentration of denaturants.

Detection of the antigenic peptides in pHLA complexes by ultrafiltration-high performance liquid chromatography / 生物工程学报

Recombinant HLA-Ⅰ molecules/antigenic peptide complexes (pHLA complexes) are applied in the research of human T cell-specific immune responses. The preparation of pHLA complex is based on genetic engineering and protein in vitro dilution and folding-refolding technology. In an in vitro refolding system, recombinant HLA-Ⅰ molecules correctly fold and bind with antigenic peptides to form complexes. In this study, ultrafiltration-high performance liquid chromatography (ultrafiltration-HPLC) was used for quantitative determination of the antigenic peptides in recombinant pHLA complexes, especially for those in a small amount of prepared products. By adding the recombinant HLA-Ⅰ molecules and antigenic peptides into the refolding buffer, the heavy chain (HC) and light chain (β2m) of recombinant HLA-Ⅰ molecules were refolded and bond with the VYF antigenic peptide containing anchor residues to form a pHLA complex. The unbound free antigenic peptide VYF was removed by ultrafiltration to retain the complex. Finally, the pHLA complex was treated by acid to destroy its interaction, thus releasing the antigenic peptide. The results showed that the prepared recombinant pHLA complex was recognized by HLA-Ⅰ molecule specific antibody W6/32, which indicated that the recombinant HLA-Ⅰ class molecule had correct folding and was identified as pHLA complex. The antigen peptide VYF contained in the pHLA complex was also detected by ultrafiltration-HPLC, so it is feasible to apply ultrafiltration-HPLC for determination of pHLA complex. Compared with Western blotting, the concentration of antigenic peptides detected by ultrafiltration-HPLC was 0-9 μg/mL. The binding conditions can be optimized according to the amount of antigenic peptides bound in the complex in order to improve the folding efficiency of HLA-Ⅰ molecules and promote the binding of HLA-Ⅰ molecules to antigenic peptides. The production rate of pHLA complexes in the refolding system can also be calculated according to the content of antigenic peptides bound by pHLA complexes. Therefore, ultrafiltration-HPLC in this study can be used for the quality control of the preparation process of pHLA complexes, and may facilitate the research of T cell-specific immunity, artificial antigen-presenting cells, and development of specific tetramer probe applications.

Elimination of PICC catheter refolding malposition by using the supporting guide wire / 中国实用护理杂志

Objective@#To explore the use of supporting guide wire to exclude the PICC catheter refolding malposition,and reduce the number of the catheter resetting and the average time of catheter resetting,while reducing the mechanicalness phlebitis and the incidence of symptomatic thrombosis.@*Methods@#A total of 3 513 patients who received PICC from September 2016 to August 2018 were enrolled. The patients were divided into control group (1 757 cases) and observation group (1 756 cases) by random number table method.The control group was treated with conventional B-ultrasound guided modified Sadinger technique PICC. After the observation group was finished on the basis of the control group, the support guide wire was partially withdrawn and re-sent, according to whether the guide wire was re-supplied or not, to determine whether the catheter has a partial fold in the body. The incidence of catheter refolding malposition, the number of reductions, the time of reduction, and the incidence of mechanicalness phlebitis and symptomatic thrombosis were compared between the two groups.@*Results@#The refolding malposition rate of the observation group and the control group were 0 and 3.47%(61/1 757), respectively. The difference was statistically significant (χ2=59.943, P<0.01). Among the 74 patients in the observation group who underwent catheter resetting, 63 patients were reset ≤1 times, 9 patients were reset twice, 2 patients were reset≥third; among the 61 patients in the control group who underwent catheter resetting, 24 patients were reset≤1 times, 6 patients were reset twice, 31 patients were reset≥third, the number of the resetting in two groups were compared,the difference was statistically significant(χ2=42.712, P<0.05). The average reset time of the observation group was (49.66±25.45) s, and the average reset time of the control group was (610.41±206.23) s, the difference was statistically significant (t=18.636, P<0.01).The incidence of mechanical phlebitis in the observation group and the control group were 1.31%(23/1 756) and 3.76%(66/1 757), respectively. The incidence of mechanical phlebitis in the two groups was statistically significant (χ2=20.241, P<0.01). The incidence of symptomatic thrombosis in the observation group and the control group were 0.34%(6/1 756), 1.20%(21/1 757), respectively. The incidence of symptomatic thrombosis in the two groups was statistically significant (χ2=8.261, P<0.05).@*Conclusions@#The use of the supportting guide wire to withdraw and re-feed during the catheterization process can effectively eliminate the PICC catheter refolding malposition, reduce the number of catheter reposition and the average reposition time, and reduce the incidence of mechanicalness phlebitis and symptomatic thrombosis. This method is simple and easy to use, it is worthy of clinical application.

Elimination of PICC catheter refolding malposition by using the supporting guide wire / 中国实用护理杂志

Objective To explore the use of supporting guide wire to exclude the PICC catheter refolding malposition,and reduce the number of the catheter resetting and the average time of catheter resetting,while reducing the mechanicalness phlebitis and the incidence of symptomatic thrombosis. Methods A total of 3 513 patients who received PICC from September 2016 to August 2018 were enrolled. The patients were divided into control group (1 757 cases) and observation group (1 756 cases) by random number table method.The control group was treated with conventional B-ultrasound guided modified Sadinger technique PICC. After the observation group was finished on the basis of the control group, the support guide wire was partially withdrawn and re-sent, according to whether the guide wire was re-supplied or not, to determine whether the catheter has a partial fold in the body. The incidence of catheter refolding malposition, the number of reductions, the time of reduction, and the incidence of mechanicalness phlebitis and symptomatic thrombosis were compared between the two groups. Results The refolding malposition rate of the observation group and the control group were 0 and 3.47%(61/1 757), respectively. The difference was statistically significant (χ2=59.943, P＜0.01). Among the 74 patients in the observation group who underwent catheter resetting, 63 patients were reset≤1 times, 9 patients were reset twice, 2 patients were reset≥third;among the 61 patients in the control group who underwent catheter resetting, 24 patients were reset≤1 times, 6 patients were reset twice,31 patients were reset≥third,the number of the resetting in two groups were compared,the difference was statistically significant (χ2=42.712, P＜0.05). The average reset time of the observation group was (49.66 ± 25.45) s, and the average reset time of the control group was (610.41±206.23) s, the difference was statistically significant (t=18.636, P＜0.01).The incidence of mechanical phlebitis in the observation group and the control group were 1.31%(23/1 756) and 3.76%(66/1 757), respectively. The incidence of mechanical phlebitis in the two groups was statistically significant (χ2=20.241, P＜0.01). The incidence of symptomatic thrombosis in the observation group and the control group were 0.34% (6/1 756), 1.20% (21/1 757), respectively. The incidence of symptomatic thrombosis in the two groups was statistically significant (χ2=8.261, P＜0.05). Conclusions The use of the supportting guide wire to withdraw and re-feed during the catheterization process can effectively eliminate the PICC catheter refolding malposition, reduce the number of catheter reposition and the average reposition time, and reduce the incidence of mechanicalness phlebitis and symptomatic thrombosis. This method is simple and easy to use, it is worthy of clinical application.

Development of Refolding Process to Obtain Active Recombinant Human Bone Morphogenetic Protein-2 and its Osteogenic Efficacy on Oral Stem Cells

BMP-2 is a well-known TGF-beta related growth factor, having a significant role in bone and cartilage formation. It has been employed to promote bone formation in some clinical trials, and to differentiate mesenchymal stem cells into osteoblasts. However, it is difficult to obtain this protein in its soluble and active form. hBMP-2 is expressed as an inclusion body in the bacterial system. To continuously supply hBMP-2 for research, we optimized the refolding of recombinant hBMP-2 expressed in E. coli, and established an efficient method by using detergent and alkali. Using a heparin column, the recombinant hBMP-2 was purified with the correct refolding. Although combinatorial refolding remarkably enhanced the solubility of the inclusion body, a higher yield of active dimer form of hBMP-2 was obtained from one-step refolding with detergent. The refolded recombinant hBMP-2 induced alkaline phosphatase activity in mouse myoblasts, at ED₅₀ of 300-480ng/ml. Furthermore, the expressions of osteogenic markers were upregulated in hPDLSCs and hDPSCs. Therefore, using the process described in this study, the refolded hBMP-2 might be cost-effectively useful for various differentiation experiments in a laboratory.

Expresión y renaturalización del antígeno protector de Bacillus anthracis: un modelo para evaluar el replegado de proteínas antigénicas recombinantes a gran escala / Expression and refolding of the protective antigen of Bacillus anthracis: A model for high-throughput screening of antigenic recombinant protein refolding

Bacillus anthracis protective antigen (PA) is a well known and relevant immunogenic protein that is the basis for both anthrax vaccines and diagnostic methods. Properly folded antigenic PA is necessary for these applications. In this study a high level of PA was obtained in recombinant Escherichia coli. The protein was initially accumulated in inclusion bodies, which facilitated its efficient purification by simple washing steps; however, it could not be recognized by specific antibodies. Refolding conditions were subsequently analyzed in a high-throughput manner that enabled nearly a hundred different conditions to be tested simultaneously. The recovery of the ability of PA to be recognized by antibodies was screened by dot blot using a coefficient that provided a measure of properly refolded protein levels with a high degree of discrimination. The best refolding conditions resulted in a tenfold increase in the intensity of the dot blot compared to the control. The only refolding additive that consistently yielded good results was L-arginine. The statistical analysis identified both cooperative and negative interactions between the different refolding additives. The high-throughput approach described in this study that enabled overproduction, purification and refolding of PA in a simple and straightforward manner, can be potentially useful for the rapid screening of adequate refolding conditions for other overexpressed antigenic proteins.

El antígeno protector de Bacillus anthracis (protective antigen, PA) es una importante proteína inmunogénica, en la que se basan tanto las vacunas contra el ántrax/carbunclo como varios métodos diagnósticos. Para estas aplicaciones es esencial que el PA mantenga sus propiedades antigénicas, para lo cual debe estar correctamente plegado. En este estudio se obtuvieron altos niveles del PA en Escherichia coli recombinante. Inicialmente, la proteína se acumuló desnaturalizada en cuerpos de inclusión, lo que facilitó su eficiente purificación en simples pasos de lavado, pero no fue reconocida por anticuerpos específicos. Se analizaron las condiciones de replegado con un sistema de alto rendimiento, evaluando simultáneamente casi un centenar de condiciones diferentes. La recuperación de la capacidad del PA de ser reconocido por los anticuerpos se evaluó por dot blot utilizando un coeficiente que proporcionó una medida de los niveles de proteína correctamente plegada, con un alto grado de discriminación. Las mejores condiciones de renaturalización permitieron un aumento de diez veces en la intensidad de los dot blots con respecto del control. El único aditivo que produjo buenos resultados de forma constante fue la L-arginina. El análisis estadístico de las interacciones entre los diferentes aditivos de replegado permitió identificar tanto interacciones cooperativas como negativas. El enfoque de alto rendimiento descripto en este trabajo, que permitió la sobreproducción, purificación y plegado del PA de una manera sencilla y directa, puede ser potencialmente útil para el rápido screening de las condiciones adecuadas de replegado cuando se sobreexpresan otras proteínas antigénicas.

Cristalización y predicción de la estructura tridimensional de la proteína homóloga del receptor activado para la quinasa c (lack) de leishmania / Crystallization and prediction of three-dimensional structure of the homologue protein of the receptor for activated c-kinase (lack) from leishmania / Cristalização e predição da estrutura tridimensional da proteína homologa do receptor ativado para a quinasa c (lack) de leishmania

Los parásitos del género Leishmania son los causantes de la enfermedad conocida como Leishmaniasis. Esta enfermedad es endémica en 98 países. Veinte especies de Leishmania sp han sido descritas como patógenos en humanos y varias de ellas presentan manifestaciones clínicas diferentes. No se dispone de vacuna, a pesar del considerable esfuerzo de muchos grupos de investigación. Las alternativas para descubrir nuevos medicamentos están basadas en el diseño de compuestos que interaccionen con blancos específicos, principalmente, proteínas encargadas de procesos metabólicos o celulares del patógeno, e.g. la parasitación de las células del huésped vertebrado. La eficiente parasitación del huésped vertebrado por Leishmania depende de la expresión de diferentes proteínas, incluyendo la proteína Lack. Parásitos deficientes de Lack no sobreviven internalizados en las células de los vertebrados. Este artículo presenta las condiciones de renaturalización, purificación y cristalización de la proteína Lack del patógeno humano Leishmania (Viannia) panamensis. Además, los resultados de modelación estructural de esta proteína muestran una conformación proteica similar a un ventilador organizado en 7 aspas, cada una compuesta de 4 hojas β. La estructura de la proteína Lack resultó similar a la proteína asociada a ribosoma RACK1 de Trypanosoma brucei y Saccharomyces cerevisiae, y a la de otros eucariotas. Las características estructurales de la proteína Lack podrían ser usadas para la exploración de nuevos.

Leishamnia parasites are the causative agents of the leishmaniasis disease. Due to its broad distribution, parasites are endemic in approximately 98 countries. Twenty species of Leishmaniasp has been described as human pathogens and several of them present different clinical manifestations. This feature poses a significant challenge to the general goals of parasite control and erradication. There is no a protective vaccine for humans, despite substantial efforts by many research teams. Alternatives to discover new drugs are based on the design of new compounds that bind selected targets. Mainly, the targets are proteins involved in key metabolic or cellular processes of the pathogen, e.g. parasitization of vertebrate host cells. The efficient parasitization of the vertebrate host by Leishmania parasites depends on the expression of different molecules including Lack protein. The knockout parasites fail to survive inside the vertebrate host cells. In this article we highlight the conditions to perform the refold, purification, and crystallizing of the Lack protein of the human pathogen Leishmania (Viannia) panamensis. Moreover, we present structure modelling analysis which shows a protein conformation like a fan organized in 7 blades, each one composed of 4 b sheets. Furthermore, the structure of Lack protein was found to be similar to RACK1-ribosome associated protein from Trypanosoma brucei and Saccharomyces cerevisiae and other eukaryotes. The structural characteristics of Lack protein could be used for exploration of new drugs.

Os parasitas do gênero Leishmania são os agentes causadores da doença conhecida como Leishmaniasis. Esta doença é endêmica em 98 países. Vinte espécies de Leishmania sp têm sido descritas como patógenos em humanos e várias delas apresentam manifestações clínicas diferentes. Não se dispõe de vacina, apesar do considerável esforço de muitos grupos de pesquisa. As alternativas para descobrir novos medicamentos estão baseadas no desenho de compostos que interajam com alvos específicos, principalmente, proteínas encarregadas de processos metabólicos ou celulares do patógeno, e.g. a parasitação das células do hóspede vertebrado. A eficiente infestação do hóspede vertebrado por Leishmania depende da expressão de diferentes proteínas, incluindo a proteína Lack. Parasitas deficientes de Lack não sobrevivem internalizados nas células dos vertebrados. Este artigo apresenta as condições de regeneração, purificação e cristalização da proteína Lack do patogénico humano Leishmania (Viannia) panamensis. Além disso, resultados de modelação estrutural desta proteína mostram uma conformação protéica similar a um ventilador, organizado em 7 pás, cada uma composta de 4 folhas β. A estrutura da proteína Lack resultou similar a proteína associada ao ribossomo RACK1 de Trypanosoma brucei y Saccharomyces cerevisiae, e à de outros eucariotas. As características estruturais da proteína Lack poderiam ser usadas para a pesquisa de novos fármacos.

Comparison in purification methods of the recombinant human cardiac troponin I / 国际检验医学杂志

Objective To compare the two kinds of purification method for purifying recombinant human cardiac troponin I(cT-nI)to obtain the stable cTnI and promote the study of cTnI diagnosis standardization.Methods The cTnI inclusion body was ob-tained by the ultrasonic broken engineering,after washing by 2% Tritonx-100,2M urea,dissolved in 8M urea,then purified by the column refolding on CM-FF and the dilution refolding respectively.The cTnI yields were compared between the two kinds of meth-od and the stability at 4 ℃,20 ℃,-80 ℃ and on the freeze-dried condition was compared.Then the purification method to effi-ciently obtain the stable cTnI was established.Results The protein about 2 mg and 1.4 mg could be obtained by CM-FF on the col-umn refolding and the dilution refolding from 0.1 g of wet inclusion body,respectively.The former method had the short cycle and high efficiency.The cTnI purified by the column refolding on CM-FF was more stable at 4 ℃,20 ℃,-80 ℃ and on the freeze-dried condition.Conclusion The column refolding on CM-FF is more stable and highly efficient in purification of cTnI than the dilution refolding.

Effect of inactivation and reactivation conditions on activity recovery of enzyme catalysts

Enzymes are labile catalysts with reduced half-life time that can be however improved by immobilization and, furthermore, already inactivated catalyst can be recovered totally or partially, therefore allowing the large scale application of enzymes as process catalysts. In recent years a few studies about reactivation of enzyme catalysts have been published as a strategy to prolong the catalyst lifetime. Reported results are very good, making this strategy an interesting tool to be applied to industrial process. These studies have been focused in the evaluation of different variables that may have a positive impact both in the rate and level of activity recovery, being then critical variables for conducting the reactivation process at productive scale. The present work summarizes the studies done about reactivation strategies considering different variables: type of immobilization, enzyme-support interaction, level of catalyst inactivation prior to reactivation, temperature and presence of modulators.

Refolding of recombinant human granulocyte colony stimulating factor: Effect of cysteine/cystine redox system.

Granulocyte colony-stimulating factor (G-CSF) is a multi-functional cytokine which is widely used for treating neutropenia in humans. Evaluation of alternative to expensive components of redox buffer (reduced and oxidized glutathione) is an important step in reducing the cost of production of human biotherapeutic proteins. In the present study, refolding of recombinant human G-CSF expressed as inclusion bodies (IBs) in E. coli was optimized using cysteine and cystine redox agents. The refolding to correct native form of G-CSF was assessed by reverse phase high performance liquid chromatography (RP-HPLC). The optimized concentrations of cysteine and cystine for correct refolding of G-CSF were found to be 2 mM and 1 mM, respectively. The correctly refolded G-CSF was detected as early as 4 h of incubation in renaturation buffer containing optimized concentrations of cysteine (2 mM) and cystine (1 mM) redox agents. Refolding of G-CSF in optimized redox system increased with increase in shuffling time. Overall, the results suggested the use of cysteine/cystine redox pair could be an alternative to the costlier redox pairs for successful refolding of G-CSF and possibly other human biotherapeutic proteins of importance.

Leishmania (Viannia) panamensis expresses a nuclease with molecular and biochemical features similar to the Endonuclease G of higher eukaryotes / Leishmania (Viannia) panamensis expresa una nucleasa molecular y bioquímicamente similar a la Endonucleasa G de eucariotas superiores

Objective: To characterize the molecular and biochemical features of the Endonuclease G of Leishmania (Viannia) panamensis.Methods: The gene of the putative L. (V.) panamensis Endonuclease G was amplified, cloned, and sequenced. The recombinant protein was produced in a heterologous expression system and biochemical assays were run to determine its ion, temperature, and pH preferences.Results: The L. (V.) panamensis rENDOG has biochemical features similar to those found in other trypanosomatids and higher eukaryotes. In addition, phylogenetic analysis revealed a possible evolutionary relationship with metazoan ENDOG.Conclusions: L. (V.) panamensis has a gene that codifies an ENDOG homologous to those of higher organisms. This enzyme can be produced in Escherichia coli and is able to degrade covalently closed circular double-stranded DNA. It has a magnesium preference, can be inhibited by potassium, and is able to function within a wide temperature and pH range.

Objetivo: Caracterizar molecular y bioquímicamente la Endonucleasa G (EndoG) de Leishmania (Viannia) panamensis.Métodos: El gen de la putativa Endonucleasa G de L. (V.) panamensis fue amplificado, clonado y secuenciado. La proteína recombinante se produjo en un sistema de expresión heterólogo y la proteína activa se sometió a pruebas bioquímicas para determinar la preferencia de iones, temperatura y pH.Resultados: La rEndoG de L. (V.) panamensis muestra características bioquímicas similares a aquellas descritas en otros trypanosomatidos y en eucariotas superiores. Además, los análisis filogenéticos muestran una posible relación evolutiva con la Endonucleasa G de metazoos.Conclusiones: Leishmania (V.) panamensis posee un gen que codifica para una endonucleasa homóloga a la EndoG de otros organismos superiores, que se puede producir de forma recombinante en Escherichia coli y que es capaz de degradar ADN circular cerrado de doble cadena. Tiene una preferencia por los iones magnesio y manganeso para usarlos como cofactor y es inhibida por el potasio. Además, funciona en un amplio rango de pH y temperatura.

Recombinant expression and refolding of the c-type lysozyme from Spodoptera litura in E. coli

The chicken-type lysozyme of the insect Spodoptera litura (SLLyz) is a polypeptide of 121 amino acids containing four disulfide bridges and 17 rare codons and participates in innate defense as an anti-bacterial enzyme. The recombinant S. litura lysozyme (rSLLyz) expressed as a C-terminal fusion protein with glutathione S-transferase (GST) in Rosetta(DE3) Singles. The protein was produced as an inclusion body which was solubilized in 8 M urea, renatured by on-column refolding, and purified by reversed-phase chromatography to 95 percent purity. The purified rSLLyz demonstrated antibacterial activity against B. megaterium confirmed by inhibition zone assay. The overexpression and refolding strategy described in this study will provide a reliable technique for maximizing production and purification of proteins expressed as inclusion bodies in E. coli.

Optimization of recombinant human endostatin refolding / 基础医学与临床

Objective To optimize the conditions for enhancing the refolding of a novel recombinant human(rh)endostatin and test the biological activities of refolded endostatin.Methods The partial purified inclusion bodies of rh-endostatin were dissolved with 6 mol/L guanidine-HCl followed by combination of dilution and dialysis of the dissolved endostatin.The refolded endostatin was then purified by cation-exchange chromatography.The biological activities of purified rh-endostatin were assessed by endostatin-specific monoclonal antibody and chick embryo chorioallantoic membrane assay.Results A 46% refolding yield was achieved after optimizing the refolding conditions.The purified endostatin reacted with specific anti-endostatin monoclonal antibody and showed significant inhibition of angiogenesis in chick embryo ehorioallantoic membrane assay.Conclusion The method of highest refolding yield of human endostatin was developed.This optimized method significantly promotes the application of this novel human endostatin to preclinical and clinical studies.

Influencing factors in the refolding process of artificial molecular chaperone assisting chicken IL-18 recombination protein / 中国兽医学报

The recombinant plasmid of mChlL-18 prokaryotic expression was transformed into E.coli BL21(DE3) strain and then induced by IPTG at 37℃.After crushed and washed,the expressing inclusion bodies were thoroughly denatured with 6 mol/L guanidine hydrochloride.Then according to experiment design,the effects of rChlL-18 protein refolding yield at different densities were investigated by the systems of artificial chapercne at different densities.Experiment results indicate that there is a optimal condition on assiting rChIL-18 protein by using the artificial chaperone technique.The optimal condition can improve the refolding yield of rChIL-18 protein,and then the expressed product of fusion chicken IL-18 gene in E.coli has a relativity high bioactivity.

Assistance of Eudragit S-100 on protein refolding / 中国药科大学学报

Aim: To study the effect of Eudragit S-100, a pH-responsive polymer, on protein refolding level, using recombinant human keratinocyte growth factor-2 (rhKGF-2) as a model protein. Methods: The refolding of rh-KGF-2 was performed by directly diluting denatured rhKGF-2 into a refolding buffer containing different concentrations of Eudragit. The ability of Eudragit S-100 to enhance protein refolding level was investigated using MTT assay, reverse phase HPLC, fluorescence emission spectroscopy and circular dichroism spectroscopy. Results: The addition of Eudragit S-100 in the refolding buffer significantly increased the rhKGF-2 refolding yield to 71%, when dilution refolding was conducted at 0. 5 mg/mL rhKGF-2. The outcome from the refolding study showed possibility of a special interaction between rhKGF-2 and Eudragit, suggesting that the refolding-enhancing ability of Eudragit S-100 was due to this interaction between Eudragit S-100 and rhKGF-2. Mean while, the result showed that the concentration of urea was also an important factor for the optimization of the refolding in the presence of Eudragit. Conclusion: Eudragit S-100 can significantly increase the refolding level of rhKGF-2.

Production of the refolded oligopeptide-binding protein (OppA) encoded by the citrus pathogen Xanthomonas axonopodis pv. citri

The oligopeptide-binding protein, OppA, binds and ushers oligopeptide substrates to the membrane-associated oligopeptide permease (Opp), a multi-component ABC-type transporter involved in the uptake of oligopeptides expressed by several bacterial species. In the present study, we report the cloning, purification, refolding and conformational analysis of a recombinant OppA protein derived from Xanthomonas axonopodis pv. citri (X. citri), the etiological agent of citrus canker. The oppA gene was expressed in Escherichia coli BL21 (DE3) strain under optimized inducing conditions and the recombinant protein remained largely insoluble. Solubilization was achieved following refolding of the denatured protein. Circular dichroism analysis indicated that the recombinant OppA protein preserved conformational features of orthologs expressed by other bacterial species. The refolded recombinant OppA represents a useful tool for structural and functional analyses of the X. citri protein.

Recovery of IgG binding capability of human FcγRⅡa refolded by rapid dilution expressed in E. coli / 中华微生物学和免疫学杂志

Objective To study the effect of soluble, refolded, recombinant extracellular domain of the human Fc gamma receptor Ⅱ a (huFcγRⅡa) on the binding of human IgG to cells. Methods Extra-cellular domain of the huFcγRⅡ a gene was amplified from recombinant plasmid pe3huR Ⅱ by PCR and then cloned into pET-28a vector. The recombinant plasmid pETshuR Ⅱ was transformed into E. coli BL21 (DE3) after identified by PCR and doubly digested. The inclusion bodies of fusion protein were extracted and purified by washing, dissolved in 6 mol/L guanidine buffer, and refolded by rapid dilution technique. The refolding protein activity was tested by ELISA and flow cytometry. Results Extraceilular domain of the huFcγRⅡa gene was successfully cloned into pET-28a. The results of SDS-PAGE showed that the molecular mass (Mr) of the expressed protein was 24.8 × 103, and the expression rate was 30%. The purity of recom-binant shuR Ⅱ was up to 90% after washing. ELISA showed that the recombinant shuR Ⅱ was able to bind human IgG in a dose dependent manner, shuRⅡ could competitively inhibit the binding of human IgG to huFcγRⅡa expressed on the surface of COS-7 cells by flow cytometry. Conclusion The results demon-strate that it is possible to obtain large quantities of recombinant shuR Ⅱ which has comparable binding prep-erties to those of the whole membrane bound huFcγR Ⅱ a.

Site-directed Mutagenesis and Enzymatic Activity Assay of Gln49-Phospholipase A_2 Mutant / 中国生物工程杂志

In order to confirm the role that the 49th amino acid residue plays in enzymatic inactivity of Glutamine 49 phospholipase A2(Gln49-PLA2),site-directed mutagenesis of its 49th amino acid gene codon was conducted using PCR.Aspartic acid 49 phospholipase A2(Asp49-PLA2-Q49D-PLA2),the mutant of Gln49-PLA2 was expressed in E.coli with pET32a+ vector.The fusion protein,expressed as inclusion body,after being denatured,was on-column refolded and purified by immobilized metal affinity chromatography(IMAC),and then cleaved by Factor Xa.The mature Q49D-PLA2 mutant was obtained by Hitrap SP cation exchange and Superdex 75 gel filtration chromatography,with the recovery rate of 1.3%,and the specific activity of the mature Q49D-PLA2 mutant was 72 U/mg.It has been demonstrated that the 49th glutamine amino acid residue is the main reason in enzymatic inactivity of Gln49-PLA2 and the results are helpful for denatured protein refolding,especially in rich disulfide bonds conditions.

Comparison of Recombinant Human ?-NGF from E.coli and CHO in Biochemical Characters / 中国生物工程杂志

Though prokaryotic cells could hardly express recombinant human beta nerve growth factor (rhNGF-?) with a proper three-dimensional conformation, using of E. coli as a host for industrial production of rhNGF-? is controversial. Recombinant human beta NGF was expressed in E. coli and was refolded in vitro. The isolated products was shown to be consistent with those expressed and secreted by CHO cells in biochemical characters by SDS-PAGE, RP-HPLC, mass spectrometry, N terminal analysis and bioassay determined using DRG and PC12 cells. The products can be acquired with 95% purity, 1.8 ng/U biological activity from both expression system,which remain invariable biological activity when lyophilized in excipient and store at 37℃?2℃, RH 75%?5% for 3 months. Moreover, the product refolded from inclusion bodies of E. coli shows the predominance in homogeneity and the lower cost.

Expression,purification and bioactivity identification of recombinant SCR15-18 domain of human soluble complement receptor type 1 / 第三军医大学学报

Objective To prepare highly expressed, purified and refolded SCR15-18 of human soluble complement receptor type 1 (sCR1-SCR15-18) protein. Methods The expression of recombinant pET32-sCR1-SCR15-18 in E.coli.. BL21 was induced by IPTG of different concentrations for different time period under different temperatures and the bacteria were split by sonication. The sCR1-SCR15-18 protein was purified by Ni2+-NTA resin affinity chromatography. The purified protein was refolded under different conditions. Then the bioactivity of the protein was analyzed. Results The sCR1-SCR15-18 protein of high expression, purity and bioactivity was attained. Conclusion The parameters of expression, purification and refolding of sCR1-SCR15-18 protein were optimized, which may pave a way for further studies.