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- Fexby, Sara, et al.
(författare)
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Improved partitioning in aqueous two-phase system of tyrosine-tagged recombinant lactate dehydrogenase
- 2002
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Ingår i: Protein Expression and Purification. - 1046-5928. ; 25:2, s. 9-263
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Tidskriftsartikel (refereegranskat)abstract
- The partitioning of Bacillus stearothermophilus lactate dehydrogenase (LDH) in an aqueous two-phase system was studied. Particularly, the influence of tyrosine tags on the partitioning was evaluated. The hydrophobic effect, caused by the addition of tyrosine residues, was determined in a system based on dextran and the thermoseparating ethylene oxide-propylene oxide random copolymer (EO30PO70). Five different LDH variants were constructed with N-terminal tags containing tyrosines (Y3 and Y6), tyrosines and prolines (Y3P2 and Y6P2), and only prolines (P2). LDH fused with tags containing tyrosines increased the partitioning coefficient, and the more tyrosines added to the protein, the larger improvement in partitioning. When prolines were added between the tyrosine-rich tag and the protein, a further increased partitioning was obtained. The enhanced partitioning was attributed to the rigid structure of the proline, which in turn led to an increase in the exposure of the tag to the surroundings. The best tyrosine tag, Y6P2, increased the partition coefficient four times and additionally, a higher thermostability was observed.
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| 2. |
- Halbhuber, Z, et al.
(författare)
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Overexpression and purification of recombinant membrane PsbH protein in Escherichia coli.
- 2003
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Ingår i: Protein Expression and Purification. - 1046-5928. ; 32:1, s. 18-27
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we featured an expression system that enables the production of sufficient quantities (~mg) of low molecular weight membrane protein of photosystem II, PsbH protein, for solid-state NMR as well as other biophysical studies. PsbH gene from cyanobacterium Synechocystis sp. PCC 6803 was cloned into a plasmid expression vector, which allowed expression of the PsbH protein as a glutathione-S transferase (GST) fusion protein in Escherichia coli BL21(DE3) cells. A relatively large GST anchor overcomes foreseeable problems with the low solubility of membrane proteins and the toxicity caused by protein incorporation into the membrane of the host organism. As a result, the majority of fusion protein was obtained in a soluble state and could be purified from crude bacterial lysate by affinity chromatography on immobilized glutathione under non-denaturing conditions. The PsbH protein was cleaved from the carrier protein with Factor Xa protease and purified on DEAE–cellulose column with yields of up to 2.1 g protein/ml of bacterial culture. The procedure as we optimized is applicable for isolation of small membrane proteins for structural studies.
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| 7. |
- Nourizad, N., et al.
(författare)
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Methylotrophic yeast Pichia pastoris as a host for production of ATP-diphosphohydrolase (apyrase) from potato tubers (Solanum tuberosum)
- 2003
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Ingår i: Protein Expression and Purification. - 1046-5928 .- 1096-0279. ; 27:2, s. 229-237
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Tidskriftsartikel (refereegranskat)abstract
- ATP-diphosphohydrolase (apyrase) catalyzes the hydrolysis of phosphoanhydride bonds of nucleoside tri- and di-phosphates in the presence of divalent cations. This enzyme has broad substrate specificity for nucleotides, which makes it an ideal enzyme for different biotechnical applications, such as DNA sequencing and platelet-aggregation inhibition. The only commercially available apyrase is isolated from potato tubers. To avoid batch-to-batch variations in activity and quality, we decided to produce a recombinant enzyme. The methylotrophic yeast Pichia pastoris was chosen as an eukaryotic expression host. The coding sequence of potato apyrase, without the signal peptide, was cloned into the YpDC541 vector to create a fusion with the alpha-mating secretion signal of Saccharomyces cerevisiae. The gene was placed under the control of the methanol-inducible alcohol oxidase promoter. The YpDC541-apyrase construct was integrated into P. pastoris strain SMD1168. Methanol induction resulted in secretion of apyrase to a level of 1 mg/L. The biologically active recombinant apyrase was purified by hydrophobic interaction and ion exchange chromatography. According to SDS-PAGE and Western blot analysis, the purified enzyme showed to be hyperglycosylated. By enzymatic removal of N-glycans, a single band corresponding to a molecular mass of 48 kDa was detected. The recombinant apyrase was found to function well when it was used in combination with the Pyrosequencing technology.
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| 8. |
- Poliakov, Anton, et al.
(författare)
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Expression and purification of recombinant full-length NS3 protease-helicase from a new variant of Hepatitis C virus
- 2002
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Ingår i: Protein Expression and Purification. - 1046-5928 .- 1096-0279. ; 25:3, s. 363-371
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Tidskriftsartikel (refereegranskat)abstract
- Viral mRNA extracted from the serum of a patient infected with HCV strain I a was used for cloning, expression, and purification of full-length Hepatitis C NS3 protein. Sequencing of the protease gene identified the virus to be a new variant closely related to strain H77, differing in 15 out of 631 amino acids in the NS3 protein, none of which were predicted to be directly involved in catalysis, binding of substrate, or cofactor. A pBAD expression system was used to express the enzyme with an N-terminal tag in Escherichia coli. Purification from the soluble cellular fraction was achieved by Ni2(+)-IMAC and PolyU Sepharose affinity chromatography. The dependence of the proteolytic activity of the full-length NS3 protein on ionic strength, glycerol concentration, and a peptide corresponding to the activating region of NS4A was analyzed and used to design an activity assay that is suitable for inhibition studies. The kinetic constants (k(cat) and K-M) for catalysis and the inhibitory potencies (IC50 and K-i) of five product-based hexapeptide inhibitors were comparable to those reported for the truncated NS3 protein. Detailed kinetic and inhibition studies using this variant of full-length NS3 can increase the understanding of the enzymatic characteristics of NS3, reveal the importance of the substituted amino acids and the significance of the genetic variability for design of effective inhibitors of the virus, and is thus of relevance for drug discovery.
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| 9. |
- Sjodahl, J., et al.
(författare)
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Characterization of proteinases from Antarctic krill (Euphausia superba)
- 2002
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Ingår i: Protein Expression and Purification. - 1046-5928 .- 1096-0279. ; 26:1, s. 153-161
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Tidskriftsartikel (refereegranskat)abstract
- Fractions of three trypsin-like proteinases, TL I, TL II, and TL III, a chymotrypsin-like proteinase, CL, two carboxypeptidase A enzymes, CPA I and CPA II and two carboxypeptidase B enzymes. CPB I and CPB II, from Antarctic krill (Euphausia superba) have been characterized with respect to purity by the means of capillary electrophoresis, CE, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). The masses of the trypsin-like and chymotrypsin-like proteinases were determined to be 25,020, 25,070, 25,060. and 26,260 Da for TL I, TL II, TL III, and CL, respectively. The masses of the CPA enzymes are likely 23,170 and 23,260 Da. whereas the CPB enzyme masses likely are 33,730 and 33,900 Da, The degradation efficiency and cleavage pattern of the trypsin-like proteinases were studied with native myoglobin as a model substrate using CE, MALDI-TOF-MS, and nanoelectrospray mass spectrometry (nESI-MS). The degradation efficiency of the trypsin-like proteinases was found to be approximately 12 and 60 times higher compared to bovine trypsin at 37 degreesC and 1-3 degreesC, respectively. All three fractions of trypsin-like proteinases showed a carboxypeptidase activity in combination with their trypsin activity.
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