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Results for “Protein purification”

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At least 37 records · Page 2Linked to original sources

PubMed1993

Arsenical-based affinity chromatography of vicinal dithiol-containing proteins: purification of L1210 leukemia cytoplasmic proteins and the recombinant rat c-erb A beta 1 T3 receptor.

Proteins containing vicinal dithiols were purified by affinity chromatography using Sepharose 4B linked to aminohexanoyl-4-aminophenylarsineoxide (As-Sepharose). The protein vicinal dithiols form stable dithioarsine derivatives with the arsine oxide moieties of the gel. The adsorbed proteins were eluted, at physiological pH, by buffers containing beta-mercaptoethanol or dithiothreitol. The dithiol proteins were identified by their specific labeling with N-iodoacetyl-3-[125I]-iodotyrosine. Cytoplasmic thiol proteins of L1210 murine leukemia lymphoblasts were separated into three classes by interaction with As-Sepharose. Proteins that did not bind to the gel consisted of monothiol proteins; proteins eluted by beta-mercaptoethanol include vicinal dithiol-containing proteins with low affinity for the arsine oxide. DL-Dithiothreitol (DTT) elutes a large group of vicinal dithiol-containing proteins with high affinity for the arsine groups. Gradient elution allowed characterization of the relative affinities of dithiol proteins for the As-Sepharose. A one-step purification of the L-triiodothyronine recombinant rat c-erb A beta 1 T3 receptor synthesized in yeast required pretreatment with DTT for binding to As-Sepharose and resulted in a 62-fold increase in specific activity. The procedure allows purification of proteins inhibited by phenylarsine oxide such as phosphotyrosine phosphatases, proteins that are subject to redox regulation, and dithiol proteins that are targets of oxidative stress.

Adsorption↗

PubMed1996

Bifunctional fusion proteins of calmodulin and protein A as affinity ligands in protein purification and in the study of protein-protein interactions.

An affinity chromatography system is described that incorporates a genetically designed bifunctional affinity ligand. The utility of the system in protein purification and in the study of protein-protein interactions is demonstrated by using the interaction between protein A and the heat shock protein DnaK as a model system. The bifunctional affinity ligand was developed by genetically fusing calmodulin (CaM) to protein A (ProtA). The dual functionality of protein A-calmodulin (ProtA-CaM) stems from the molecular recognition properties of the two components of the fusion protein. In particular, CaM serves as the anchoring component by virtue of its binding properties toward phenothiazine. Thus, the ProtA-CaM can be immobilized on a solid support containing phenothiazine from the C-terminal domain of the fusion protein. Protein A is at the N-terminal domain of the fusion protein and serves as the affinity site for DnaK. While DnaK binds specifically to the protein A domain of the bifunctional ligand, it is released upon addition of ATP and under very mild conditions (pH 7.0). In addition to obtaining highly purified DnaK, this system is very rugged in terms of its performance. The proteinaceous bifunctional affinity ligand can be easily removed by addition of EGTA, and fresh ProtA-CaM can be easily reloaded onto the column. This allows for a facile regeneration of the affinity column because the phenothiazine-silica support matrix is stable for long periods of time under a variety of conditions. This study also demonstrates that calmodulin fusions can provide a new approach to study protein-protein interactions. Indeed, the ProtA-CaM fusion protein identified DnaK as a cellular component that interacts with protein A from among the thousands of proteins present in Escherichia coli.

Calmodulin↗

PubMed2005

Blood protein purification and simultaneous removal of nonenveloped viruses using tangential-flow preparative electrophoresis.

Gradiflow is new technology allowing purification of important blood proteins from viral contaminated plasma. Protein purification is based on unique scalable tangential-flow preparative electrophoresis, and is distinct from current technology because protein purification and virus removal are performed in the same step. This one-step removal and purification exploits both the size and charge of target proteins. The medically important blood proteins, immunoglobulin G (IgG) and alpha-1-antitrypsin, were chosen to demonstrate the ability of this process to purify proteins from contaminated plasma. Clearance factors achieved by infectivity assays and polymerase chain reaction (PCR) that meet regulatory requirements demonstrated removal of canine parvovirus (CPV). CPV is a model virus for pathogenic nonenveloped viruses, including parvovirus B19, not adequately removed or inactivated by most processes currently in practice. The recovery of proteins from plasma with high purity, recovery, and function, while simultaneously removing viruses, provides blood products with a level of purity compatible with clinical use more quickly and cheaply than available techniques.

Blood↗

PubMed1993

A gene expression vector useful for protein purification and studies of protein-protein interaction.

This report describes the development of a gene expression vector that adds three features to the C-terminus of the putative synthesized protein: (1) a protein kinase A recognition domain allowing the protein to be radio-labeled in vitro, (2) an epitope marker for immunocharacterization of the protein with a commercial monoclonal antibody, and (3) a (His)6 block facilitating purification of the protein by metal chelating affinity chromatography. These features make it convenient to perform biochemical and functional analysis of the protein of interest.

Amino Acid Sequence↗

PubMed2006

Lectin-based affinity tag for one-step protein purification.

The production of pure protein is indispensable for many applications in life sciences, however protein purification protocols are difficult to establish, and the experimental procedures are usually tedious and time-consuming. Therefore, a number of tags were developed to which proteins of interest can be fused and subsequently purified by affinity chromatography. We report here on a novel lectin-based affinity tag using the D-mannose-specific lectin LecB from Pseudomonas aeruginosa. A fusion protein was constructed consisting of yellow fluorescent protein and LecB separated by an enterokinase cleavage site. This protein was overexpressed in Escherichia coli Tuner (DE3), and the cell extract was loaded onto a column containing a mannose agarose matrix. Electrophoretically pure fusion protein at a yield of 24 mg/L culture was eluted with a D-mannose containing buffer The determination of equilibrium adsorption isotherms revealed an association constant of the lectin to the mannose agarose matrix of Ka = 3.26 x 10(5)/M. Enterokinase treatment of the purified fusion protein resulted in the complete removal of the LecB-tag. In conclusion, our results indicate that the lectin LecB of P. aeruginosa can be used as a tag for the high-yield one-step purification of recombinant proteins.

Adsorption↗

PubMed2004

Expression screening, protein purification and NMR analysis of human protein domains for structural genomics.

Structural genomics, the determination of protein structures on a genome-wide scale, is still in its infancy for eukaryotes due to the number and size of their genes. Low protein expression and solubility of eukaryotic geneproducts are the major bottlenecks in high-throughput (HTP) recombinant protein production with the E. coli expression systems. To circumvent this problem we decided to focus on separate protein domains. We describe here a fast microtiterplate based, expression and solubility screening procedure, using a combination of in vitro and in vivo expression, and purification with nickel-NTA magnetic beads. All steps are optimized for automatic HTP processing using a liquid handling station. Furthermore, large-scale expression and protein purification conditions are optimized, permitting the purification of 24 protein samples per week. We further show that results obtained from the expression screening can be extrapolated to the production of protein samples for NMR. Starting with 81 cloned human protein domains, in vivo expression was detected in 54 cases, and from 28 of those milligrams of protein were purified. An informative HSQC spectrum was recorded for 18 proteins (22%), half of which were indicative of a folded protein. The success rate and quality of the HSQC spectra suggest that the domain approach holds promise for human proteins.

Cloning, Molecular↗

PubMed2003

Application of hydrophobic interaction displacement chromatography for an industrial protein purification.

Recently it has been established that low molecular weight displacers can be successfully employed for the purification of proteins in hydrophobic interaction chromatography (HIC) systems. This work investigates the utility of this technique for the purification of an industrial protein mixture. The study involved the separation of a mixture of three protein forms, that differed in the C-terminus, from their aggregate impurities while maintaining the same relative ratio of the three protein forms as in the feed. A batch high-throughput screening (HTS) technique was employed in concert with fluorescence spectroscopy for displacer screening in these HIC systems. This methodology was demonstrated to be an effective tool for identifying lead displacer candidates for a particular protein/stationary-phase system. In addition, these results indicate that surfactants can be employed at concentrations above their CMCs as effective displacers. Displacement of the recombinant proteins with PEG-3400 and the surfactant Big Chap was shown to increase the productivity as compared to the existing step-gradient elution process.

Chromatography↗

PubMed2005

Modified cell ELISA to determine the solubilization of cell surface proteins: Applications in GPI-anchored protein purification.

A major step in purifying membrane bound proteins involves the solubilization of the protein of interest from the cell membranes. Glycosylphosphatidyl inositol (GPI)-anchored proteins pose a singular problem in this solubilization step since they are found in detergent-resistant membrane complexes and accordingly are insoluble in cold Triton X-100. In this study we have developed a modified cell ELISA that determines the solubility of these cell surface proteins under various solubilization conditions. Using this non-radioactive method we show that the combination of saponin/Triton X-100 at 4 degrees C solubilized GPI-anchored proteins more efficiently than Triton X-100 at 4 degrees C. The combination of saponin/Triton X-100 at 4 degrees C avoids the potential of activating proteases that occurs when using Triton X-100 at 37 degrees C. Furthermore, our method also shows the saponin/Triton X-100 solubilized GPI-anchored proteins equivalent to the more expensive octyl beta-glucoside. This is a particularly important consideration in large-scale protein purification. This method obviates the need to use radioactivity, gel electrophoresis and immunoblotting procedures. The solubilization conditions determined by this modified ELISA are readily translated to the practical application of large-scale protein purification as demonstrated in the purification of two different recombinant GPI-anchored proteins, GPI-hB7-1 (CD80) and GPI-mICAM-1 (CD54).

Animals↗

PubMed1996

Cloning, sequencing and functional overexpression of the Streptococcus equisimilis H46A gapC gene encoding a glyceraldehyde-3-phosphate dehydrogenase that also functions as a plasmin(ogen)-binding protein. Purification and biochemical characterization of the protein.

We previously identified DNA sequences involved in the function of the complex promoter of the streptokinase gene from Streptococcus equisimilis H46A, a human serogroup C strain known to express this gene at a high level. As a prerequisite to understanding possible mechanisms that control the balance between the plasminogen activating and plasmin(ogen) binding capacities of H46A, we describe here its gapC gene encoding glyceraldehyde-3-phosphate dehydrogenase (GraP-DH, EC 1.2.1.12), a glycolytic enzyme apparently transported to the cell surface where it functions as a plasmin(ogen).binding protein. The gapC gene was cloned and sequenced and found to code for a 336-amino-acid polypeptide (approximately 35.9 kDa) exhibiting 94.9% sequence identity to the Plr protein from Streptococcus pyogenes shown by others to be capable of plasmin binding [Lottenberg, R., Broder, C. C., Boyle, M. D., Kain, S. J., Schroeder, B. L. & Curtiss, R. III (1992) J. Bacteriol. 174, 5204-5210]. To study the properties of the GapC protein, its gene was inducibly overexpressed in Escherichia coli from QIAexpress expression plasmids to yield the authentic GapC or (His)6GapC carrying a hexahistidyl N-terminus to permit affinity purification. Both proteins were functionally active, exhibiting specific GraP-DH activities of about 80 kat/mol (approximately 130 U/mg) after purification. Their binding parameters [association (ka) and dissociation (kd) rate constants, and equlibrium dissociation constants (Kd = kd/ka)] for the interaction with human Gluplasminogen and plasmin were determined by real-time biospecific interaction analysis using the Pharmacia BIAcore instrument. For comparative purposes, the commercial GraP-DH from Bacillus stearothermophilus (BstGraP-DH), a nonpathogenic organism, was included in these experiments. The Kd values for binding of plasminogen to GapC, (His)6GapC and BstGraP-DH were 220 nM, 260 nM and 520 nM, respectively, as compared to 25 nM, 17 nM and 98 nM, respectively, for the binding to plasmin. These data show that both the zymogen and active enzyme possess low-affinity binding sites for the gapC gene product and that the hexahistidyl terminus does not affect its function. Prior limited treatment with plasmin enhanced the subsequent plasminogen binding capacity of all three GraP-DHs, presumably by the exposure of new C-terminal lysine residues for binding to the zymogen.

Amino Acid Sequence↗

PubMed1998

Protein purification with C-terminal fusion of maltose binding protein.

For affinity-chromatography-based purification of proteins that are prone to abnormal termination of translation or that may not be modified at their N-termini, affinity tags are needed which can be fused to the C-terminus. In this publication we describe that maltose binding protein (MBP) fused to the C-terminus of the plant photoreceptor phytochrome B allows purification of the fusion protein via amylose affinity chromatography. After overexpression in yeast a 125-fold enrichment could be achieved. The spectral properties of phytochrome B were not impaired by the fusion and purification. These results demonstrate that not only the widely used N-terminal fusions of MBP but also C-terminal fusions can be employed for protein purification.

Affinity Labels↗

PubMed1998

New methods of protein purification. Displacement chromatography.

This review discusses a new method for protein purification, displacement chromatography. Elution of proteins bound to an adsorbent is carried out in displacement chromatography by a substance, the so-called "displacer", which has a higher affinity for the chromatographic matrix than any of the adsorbed proteins. The latter are "pushed out" from the matrix by the displacer and form a displacement train when moving along the column. The component with the weakest affinity moves first, and the one with the highest affinity moves last in the train. The concentration of the component in the displacement zone is determined by the intersection of the operating line and binding isotherm of the given component. The shape of the displacement zone is close to rectangular. A more powerful resolving force is created compared to other methods of selective elution, especially at high column loadings, when nearly the whole working capacity of the column is used. Independence of component concentration in the displacement zone on its content in the feed allows significant concentrating of the purified protein during displacement chromatography. Examples of application of displacement chromatography for the separation of model protein systems and purification of proteins from crude extracts are discussed as well as methods of column regeneration.

Chromatography↗

PubMed2006

High-throughput protein purification using an automated set-up for high-yield affinity chromatography.

One of the key steps in high-throughput protein production is protein purification. A newly developed high-yield protein purification and isolation method for laboratory scale use is presented. This procedure allows fully automated purification of up to 60 cell lysates with milligram yields of pure recombinant protein in 18.5h. The method is based on affinity chromatography and has been set up on an instrument that utilizes positive pressure for liquid transfer through columns. A protocol is presented that includes all steps of equilibration of the chromatography resin, load of sample, wash, and elution without any manual handling steps. In contrast to most existing high-throughput protein purification procedures, positive pressure is used for liquid transfer rather than vacuum. Positive pressure and individual pumps for each liquid channel contribute to controlled flow rates and eliminate the risk of introducing air in the chromatography resin and therefore ensure stable chromatography conditions. The procedure is highly reproducible and allows for high protein yield and purity.

Chromatography, Affinity↗

PubMed2004

Principle and applications of the protein-purification-parameter screening system.

For the purification of a target protein, liquid chromatography is the method of choice, if its activity has to be maintained. The selection of optimum parameters will improve in proportion to the number of individual parameters varied in initial experiments. Here a fast screening method is described, which utilizes automated parallel chromatographic experiments in the batch mode in 96-well plates. The principle of this protein-purification-parameter screening (PPS) system is demonstrated with a mixture of four proteins. An application of PPS for the determination of a purification step of an angiotensin-II-generating enzyme from a crude tissue extract is shown.

Animals↗

PubMed2005

Preparative parallel protein purification (P4).

In state of the art drug discovery, it is essential to gain structural information of pharmacologically relevant proteins. Increasing the output of novel protein structures requires improved preparative methods for high throughput (HT) protein purification. Currently, most HT platforms are limited to small-scale and available technology for increasing throughput at larger scales is scarce. We have adapted a 10-channel parallel flash chromatography system for protein purification applications. The system enables us to perform 10 different purifications in parallel with individual gradients and UV monitoring. Typical protein purification applications were set up. Methods for ion exchange chromatography were developed for different sample proteins and columns. Affinity chromatography was optimized for His-tagged proteins using metal chelating media and buffer exchange by gel filtration was also tested. The results from the present system were comparable, with respect to resolution and reproducibility, with those from control experiments on an AKTA purifier system. Finally, lysates from 10 E. coli cultures expressing different His-tagged proteins were subjected to a three-step parallel purification procedure, combining the above-mentioned procedures. Nine proteins were successfully purified whereas one failed probably due to lack of expression.

Automation↗

PubMed1990

An overview of continuous protein purification processes.

As the sphere of influence of recombinant technology moves away from the laboratory bench, towards product commercialization, development of manufacturing and large scale process technology is becoming a major challenge and determinant for commercial success. The challenge is particularly acute for protein purification process development where protein purification costs tend to dominate overall process economics. The primary objective for process scale purification is to minimize cost for a purified product which meets specifications. Continuous processes may be used to facilitate achievement of the overall objectives. This review critically examines the use of continuous processing for protein purification and recovery operations. The processes have been divided into three general areas: adsorptive and chromatographic, electrophoretic, and extractive. Consideration is given to the operational advantages and limitations of the reviewed processes.

Journal Article↗

PubMed1998

The chloroplast small heat shock protein--purification and characterization of pea recombinant protein.

We report here on a procedure to obtain large amounts of a chloroplast-localized heat shock protein (HSP21) with unknown structure and function, by using an Escherichia coli expression system for the pea (Pisum sativum) protein and a purification procedure based on perfusion ion-exchange chromatography. After initial precipitation steps, the sample was applied to cation- and anion-exchange on two columns connected in sequence, which allowed rapid purification of HSP21 in one equilibration and one elution step. The purified recombinant protein had an isoelectric point of 5. 0 and appeared in assembled, oligomeric form (approximately 200 kDa) composed of 21-kDa monomers, similar to the native HSP21 protein as detected by immunoblotting in plants after heat-stress treatment. This chloroplast-localized heat shock protein belongs to a special group of small heat shock proteins (sHSPs), which share an evolutionary conserved C-terminal domain with the vertebrate eye lens alpha-crystallin. The crystallins are known from both crystallographic and spectroscopic data to be all-beta proteins. In contrast, this paper presents circular dichroism spectroscopy data which shows that the purified recombinant HSP21 oligomer has a content of more than 30% alpha-helical secondary structure.

Amino Acids↗

PubMed2004

Preparative protein purification on underivatized silica.

This article describes the use of underivatized silica gel as a preparative stationary phase for process purification of proteins. Although silica has been frequently used as a stationary phase backbone matrix, direct adsorption of proteins on underivatized silica has not been widely exploited for industrial applications. In this study an effort was made to fundamentally understand the interaction mechanisms between a protein and silica surface by using several proteins with a wide range of isoelectric points (pIs) and surface hydrophobicity. Interactions in silica were found to be largely dominated by a combination of ionic and hydrophobic forces. Accordingly, a predictive model was derived for describing linear retention of proteins on silica. Finally, a case study is described investigating the role of silica in an industrial purification process. It was found that the integration of the two modes of interaction confers silica with a unique selectivity that can be very effectively utilized in downstream bioprocessing.

Animals↗

PubMed2006

Protein purification via temperature-dependent, intein-mediated cleavage from an immobilized metal affinity resin.

The intein that interrupts the DNA polymerase II DP2 subunit in Pyrococcus abyssi can be overexpressed in Escherichia coli and purified as an unspliced precursor. On in vitro incubation at 37 degrees Celsius or higher, the intein mediates efficient protein splicing. Mutations can be introduced into an intein fusion protein that prevent the second and third steps of protein splicing. As a result, the intein fusion protein can facilitate temperature-dependent formation of a thioester linkage between the N-extein and intein. This thioester is susceptible to in vitro hydrolysis or thiolysis at temperatures of 40 degrees Celsius or higher, and we have exploited this activity to generate a temperature-dependent protein purification scheme. Protein purification using this intein does not require the addition of exogenous thiols and is compatible with the use of immobilized metal affinity chromatography. The identity of the C-terminal residue of the N-extein has less influence on the cleavage reaction than in current purification systems in terms of premature in vivo cleavage and is complementary to current systems in terms of efficient in vitro cleavage.

Affinity Labels↗