Biomedical subjects

Folke Tjerneld

Publications and source records attributed to Folke Tjerneld.

30 records · Page 2Linked to original sources

PubMed2002

Partitioning of peptide-tagged proteins in aqueous two-phase systems using hydrophobically modified micelle-forming thermoseparating polymer.

Genetic engineering has been used to construct hydrophobically modified fusion proteins of cutinase from Fusarium solani pisi and tryptophan-containing peptides. The aim was to enhance the partitioning of the tagged protein in a novel aqueous two-phase system formed by only one water-soluble polymer. The system was based on a hydrophobically modified random copolymer of ethylene oxide (EO) and propylene oxide (PO) units, HM-EOPO, with myristyl groups (C(14)H(29)) at both ends. The HM-EOPO polymer is strongly self-associating and has a lower critical solution temperature (cloud point) at 12 degrees C in water. At temperatures above the cloud point a two-phase system is formed with a water top phase and a polymer-enriched bottom phase. By adding a few percent of hydroxypropyl starch polymer, Reppal PES 200, to the system, it is possible to change the densities of the phases so the HM-EOPO-enriched phase becomes the top phase and Reppal-enriched phase is the bottom phase. Tryptophan-based peptides strongly preferred the HM-EOPO rich phase. The partitioning was increased with increasing length of the peptides. Full effect of the tag as calculated from peptide partitioning data was not found in the protein partitioning. When a short spacer was introduced between the protein and the tag the partitioning was increased, indicating a better exposure to the hydrophobic core of the polymer micelle. By adding a hydrophilic spacer between the protein and trp-tag, it was possible to increase the partitioning of cutinase 10 times compared to wild-type cutinase partitioning. By lowering the pH of the system and addition of NaCl, the partitioning of tagged protein was further increased towards the HM-EOPO phase. After isolating the HM-EOPO phase, the temperature was increased and the protein was back-extracted from the HM-EOPO phase to a fresh water phase.

Amino Acid Sequence↗

PubMed2002

Enzymatic properties of the low molecular mass endoglucanases Cel12A (EG III) and Cel45A (EG V) of Trichoderma reesei.

Trichoderma reesei produces five known endoglucanases. The most studied are Cel7B (EG I) and Cel5A (EG II) which are the most abundant of the endoglucanases. We have performed a characterisation of the enzymatic properties of the less well-studied endoglucanases Cel12A (EG III), Cel45A (EG V) and the catalytic core of Cel45A. For comparison, Cel5A and Cel7B were included in the study. Adsorption studies on microcrystalline cellulose (Avicel) and phosphoric acid swollen cellulose (PASC) showed that Cel5A, Cel7B, Cel45A and Cel45Acore adsorbed to these substrates. In contrast, Cel12A adsorbed weakly to both Avicel and PASC. The products formed on Avicel, PASC and carboxymethylcellulose (CMC) were analysed. Cel7B produced glucose and cellobiose from all substrates. Cel5A and Cel12A also produced cellotriose, in addition to glucose and cellobiose, on the substrates. Cel45A showed a clearly different product pattern by having cellotetraose as the main product, with practically no glucose and cellobiose formation. The kinetic constants were determined on cellotriose, cellotetraose and cellopentaose for the enzymes. Cel12A did not hydrolyse cellotriose. The k(Cat) values for Cel12A on cellotetraose and cellopentaose were significantly lower compared with Cel5A and Cel7B. Cel7B was the only endoglucanase which rapidly hydrolysed cellotriose. Cel45Acore did not show activity on any of the three studied cello-oligosaccharides. The four endoglucanases' capacity to hydrolyse beta-glucan and glucomannan were studied. Cel12A hydrolysed beta-glucan and glucomannan slightly less compared with Cel5A and Cel7B. Cel45A was able to hydrolyse glucomannan significantly more compared with beta-glucan. The capability of Cel45A to hydrolyse glucomannan was higher than that observed for Cel12A, Cel5A and Cel7B. The results indicate that Cel45A is a glucomannanase rather than a strict endoglucanase.

Adsorption↗

PubMed2002

Primary recovery of a genetically engineered Trichoderma reesei endoglucanase I (Cel 7B) fusion protein in cloud point extraction systems.

Here we present data to demonstrate how partitioning of a hydrophilic enzyme can be directed to the hydrophobic detergent-enriched phase of an aqueous two-phase system by addition of short stretches of amino acid residues to the protein molecule. The target enzyme was the industrially important endoglucanase I, EGI (endo-1,4-beta-D-glucan-4-glucanohydrolase, EC 3.2.1.4, Cel7B) of Trichoderma reesei. We investigated the partitioning of three EGI variants containing various C-terminal peptide extensions including Trp-Pro motifs of different lengths and localizations. Additionally, a recently developed system composed of the thermoseparating copolymer HM-EOPO was utilized to study the effects of fusion tags. The addition of peptides containing tryptohan residues enhanced the partitioning of EGI to the HM-EOPO-rich phase. The system composed of a nonionic detergent (Agrimul NRE1205) resulted in the highest partition coefficient (K = 31) and yield (90%) with the construct EGI(core-P5)(WP)(4) containing (Trp-Pro)(4) after a short linker stretch. A recombinant strain of T. reesei Rut-C30 for large-scale production was constructed in which the fusion protein EGI(core-P5)(WP)(4) was expressed from the strong promoter of the cellulase gene cbh1. The fusion protein was successfully expressed and secreted from the fungus during shake-flask cultivations. Cultivation in a 28-L bioreactor however, revealed that the fusion protein is sensitive to proteases. Consequently, only low production levels were obtained in large-scale production trials.

Bioreactors↗

PubMed2002

The surface exposed amino acid residues of monomeric proteins determine the partitioning in aqueous two-phase systems.

It is of great interest and importance how different amino acid residues contribute to and affect the properties of a protein surface. Partitioning in aqueous two-phase systems has the potential to be used as a rapid and simple method for studying the surface properties of proteins. The influence on partitioning of the surface exposed amino acid residues of eight structurally determined monomeric proteins has been studied. The proteins were characterized in terms of surface exposed residues with a computer program, Graphical Representation and Analysis of Surface Properties (GRASP), and partitioned in two EO30PO70-dextran aqueous two-phase systems, only differing in polymer concentrations (system I: 6.8% EO30PO70, 7.1% dextran; system II: 9% EO30PO70, 9% dextran). We show for the first time that the partitioning behaviour of different monomeric proteins can be described by the differences in surface exposed amino acid residues. The contribution to the partition coefficient of the residues was found to be best characterized by peptide partitioning in the aqueous two-phase system. Compared to hydrophobicity scales available in the literature, each amino acid contribution is characterized by the slope given by the graph of log K against peptide chain length, for peptides of different length containing only one kind of residue. It was also shown that each amino acid contribution is relative to the total protein surface and the other residues on the surface. Surface hydrophobicity calculations realized for systems I and II gave respectively correlation coefficients of 0.961 and 0.949 for the linear relation between log K and calculated hydrophobicity values. To study the effect on the partition coefficient of different amino acids, they were grouped into classes according to common characteristics: the presence of an aromatic group, a long aliphatic chain or the presence of charge. Using these groups it was possible to confirm that aromatic residues have the strongest effect on the partition coefficient, giving preference to the upper EO30PO70 phase of the system; on the other hand the presence of charged amino acids on the protein surface enhances the partition of the protein to the lower dextran phase. It is also important to note that the sensitivity of the EO30PO70-dextran system for the surface exposed residues was increased by increasing the polymer concentrations. The partition coefficient of a monomeric protein can thus be predicted from its surface exposed amino acid residues and the system can also be used to characterize protein surfaces of monomeric proteins in general.

Amino Acids↗

PubMed2002

Characterization of water-soluble hemicelluloses from spruce and aspen employing SEC/MALDI mass spectroscopy.

Partly depolymerized hemicelluloses isolated from wood chips of spruce and aspen employing microwave treatment were resolved using size-exclusion chromatography (SEC) into oligo- and polysaccharide fractions containing components with a narrow range of sizes, as determined by MALDI mass spectroscopy. The degree of substitution with acetyl moieties (DS) was also calculated on the basis of the MALDI-MS spectra obtained prior to and following deacetylation. For spruce hemicelluloses, the low molecular mass fraction contained small arabino-4-O-methylglucuronoxylan oligosaccharides, with DP values ranging from 4 to approximately 20, separated primarily on the basis of their charge density. The fraction eluted last consisted of an O-acetyl-(galacto)glucomannan polysaccharide of peak-average DP value (DP(p)) 14. The degree of substitution with acetyl groups (DS) decreased with decreasing DP, a value DS of 0.39 being obtained for the fraction with DP(p) 12. For the aspen hemicelluloses, the SEC fractions eluted first contained an acidic O-acetyl-4-O-methylglucuronoxylan polysaccharide with DP ranging from 10 to approximately 28 and an average DS of approximately 0.75. The fractions eluted last consisted of oligosaccharide mixtures composed primarily of small neutral O-acetyl-xylooligosaccharides (DP(p) 6, DS 0.41), together with minor quantities of an O-acetyl-glucomannan.

Acetylation↗

PubMed2002

Cutinase-peptide fusions in thermoseparating aqueous two-phase systems. Prediction of partitioning and enhanced tag efficiency by detergent addition.

It is of increasing importance to develop efficient purification methods for recombinant proteins where the number of steps can be minimised. The aim has been to establish a method for predicting the partitioning of the wild-type target protein in an aqueous two-phase system, and with this as basis, develop fusion tags and optimise the phase system for enhanced partitioning of the target protein. The surface of the lipolytic enzyme cutinase from Fusarium solani pisi was investigated with a computer program, Graphical Representation and Analysis of Surface Properties (GRASP). The accessible surface areas for the different amino acid residues were used together with peptide partitioning data to calculate the partition coefficient for the protein. The separation system was composed of a thermoseparating random copolymer of ethylene oxide and propylene oxide. Breox PAG 50A 1000, as top phase forming polymer and a hydroxypropyl starch polymer, Reppal PES 200, as bottom phase polymer. The calculated partition coefficient for the wild-type protein (K= 1.0) agreed reasonably well with the experimentally determined value (K=0.85). Genetic engineering was used to construct fusion proteins expressed in Saccharomyces cerevisiae based on cutinase and peptide tags containing tryptophan, to enhance the partitioning in aqueous two-phase systems. The partitioning of the cutinase constructs could qualitatively be predicted from peptide partitioning data, i.e. the trends in partitioning could be predicted. A spacer peptide introduced between protein and tag increased the partitioning of the protein towards the ethylene oxide-propylene oxide (EOPO) copolymer top phase. The aqueous two-phase system was modified by addition of detergent to increase the partitioning of the cutinase variants towards the EOPO copolymer phase. Triton and a series of C12En detergents selectively increased the partitioning of cutinase constructs with (WP)4-based tags up to 14 times compared to wild-type cutinase. The protein partition could almost quantitatively be predicted from the peptide partition data.

Carboxylic Ester Hydrolases↗

PubMed2002

A novel two-step extraction method with detergent/polymer systems for primary recovery of the fusion protein endoglucanase I-hydrophobin I.

Extraction systems for hydrophobically tagged proteins have been developed based on phase separation in aqueous solutions of non-ionic detergents and polymers. The systems have earlier only been applied for separation of membrane proteins. Here, we examine the partitioning and purification of the amphiphilic fusion protein endoglucanase I(core)-hydrophobin I (EGI(core)-HFBI) from culture filtrate originating from a Trichoderma reesei fermentation. The micelle extraction system was formed by mixing the non-ionic detergent Triton X-114 or Triton X-100 with the hydroxypropyl starch polymer, Reppal PES100. The detergent/polymer aqueous two-phase systems resulted in both better separation characteristics and increased robustness compared to cloud point extraction in a Triton X-114/water system. Separation and robustness were characterized for the parameters: temperature, protein and salt additions. In the Triton X-114/Reppal PES100 detergent/polymer system EGI(core)-HFBI strongly partitioned into the micelle-rich phase with a partition coefficient (K) of 15 and was separated from hydrophilic proteins, which preferably partitioned to the polymer phase. After the primary recovery step, EGI(core)-HFBI was quantitatively back-extracted (K(EGIcore-HFBI)=150, yield=99%) into a water phase. In this second step, ethylene oxide-propylene oxide (EOPO) copolymers were added to the micelle-rich phase and temperature-induced phase separation at 55 degrees C was performed. Total recovery of EGI(core)-HFBI after the two separation steps was 90% with a volume reduction of six times. For thermolabile proteins, the back-extraction temperature could be decreased to room temperature by using a hydrophobically modified EOPO copolymer, with slightly lower yield. The addition of thermoseparating co-polymer is a novel approach to remove detergent and effectively releases the fusion protein EGI(core)-HFBI into a water phase.

Cellulase↗

PubMed2002

Extraction of endoglucanase I (Ce17B) fusion proteins from Trichoderma reesei culture filtrate in a poly(ethylene glycol)-phosphate aqueous two-phase system.

Endoglucanases (EGI) (endo-1,4-beta-D-glucan-4-glucanohydrolase, EC 3.2.1.4, Ce17B) of Trichoderma reesei are industrially important enzymes. Thus, there is a great need for development of a primary recovery method suitable for large-scale utilization. In this study we present a concept applicable for large-scale purification of an EGI fusion protein by one-step extraction in a poly(ethylene glycol) PEG-sodium/potassium phosphate aqueous two-phase system. EGI is a two-module enzyme composed of an N-terminal catalytic module and a C-terminal cellulose binding module (CBM) separated by a glycosylated linker region. Partitioning of six different EGI constructs, containing the C-terminal extensions (WP)2, (WP)4 or the amphiphilic protein hydrophobin I (HFB) of T. reesei instead of the CBM were studied to evaluate if any of the fusions could improve the partition coefficient sufficiently to be suitable for large-scale production. All constructs showed improved partitioning in comparison to full length EGI. The (WP)4 extensions resulted in 26- to 60-fold improvement of partition coefficient. Consequently, a relative minor change in amino acid sequence on the two-module protein EGI improved the partition coefficient significantly in the PEG 4000-sodium/potassium phosphate system. The addition of HFBI to EGI clearly enhanced the partition coefficient (K=1.2) in comparison to full-length EGI (K=0.035). Partitioning of the construct with (WP)4 fused to the catalytic module and a short sequence of the linker [EGI(core-P5)(WP)4] resulted in the highest partition coefficient (K=54) and a yield of 98% in the PEG phase. Gel electrophoresis showed that the construct with the (WP)4 tag attached after a penta-proline linker could be purified from the other bulk proteins by only a single-step separation in the PEG 4000-sodium/potassium phosphate system. This is a major improvement in comparison with the previously studied model (ethylene oxide-propylene oxide)-dextran system. Hence, this construct will be suitable for further optimization of the extraction of the enzyme in a PEG 4000-sodium/potassium phosphate system from culture filtrate.

Cellulase↗

PubMed2002

Enzymatic degradation of carboxymethyl cellulose hydrolyzed by the endoglucanases Cel5A, Cel7B, and Cel45A from Humicola insolens and Cel7B, Cel12A and Cel45Acore from Trichoderma reesei.

Enzymatic hydrolysis of carboxymethyl cellulose (CMC) has been studied with purified endoglucanases Hi Cel5A (EG II), Hi Cel7B (EG I), and Hi Cel45A (EG V) from Humicola insolens, and Tr Cel7B (EG I), Tr Cel12A (EG III), and Tr Cel45Acore (EG V) from Trichoderma reesei. The CMC, with a degree of substitution (DS) of 0.7, was hydrolyzed with a single enzyme until no further hydrolysis was observed. The hydrolysates were analyzed for production of substituted and non-substituted oligosaccharides with size exclusion chromatography (SEC) and with matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF-MS). Production of reducing ends and of nonsubstituted oligosaccharides was determined as well. The two most effective endoglucanases for CMC hydrolysis were Hi Cel5A and Tr Cel7B. These enzymes degraded CMC to lower molar mass fragments compared with the other endoglucanases. The products had the highest DS determined by MALDI-TOF-MS. Thus, Hi Cel5A and Tr Cel7B were less inhibited by the substituents than the other endoglucanases. The endoglucanase with clearly the lowest activity on CMC was Tr Cel45Acore. It produced less than half of the amount of reducing ends compared to Tr Cel7B; furthermore, the products had significantly lower DS. By MALDI-TOF-MS, oligosaccharides with different degree of polymerization (DP) and with different number of substituents could be separated and identified. The average oligosaccharide DS as function of DP could be measured for each enzyme after hydrolysis. The combination of techniques for analysis of product formation gave information on average length of unsubstituted blocks of CMC.

Ascomycota↗

PubMed2002

A model explaining declining rate in hydrolysis of lignocellulose substrates with cellobiohydrolase I (cel7A) and endoglucanase I (cel7B) of Trichoderma reesei.

It is commonly observed that the rate of enzymatic hydrolysis of solid cellulose substrates declines markedly with time. In this work the mechanism behind the rate reduction was investigated using two dominant cellulases of Trichoderma reesei: exoglucanase Cel7A (formerly known as CBHI) and endoglucanase Cel7B (formerly EGI). Hydrolysis of steam-pretreated spruce (SPS) was performed with Cel7A and Cel7B alone, and in reconstituted mixtures. Throughout the 48-h hydrolysis, soluble products, hydrolysis rates, and enzyme adsorption to the substrate were measured. The hydrolysis rate for both enzymes decreases rapidly with hydrolysis time. Both enzymes adsorbed rapidly to the substrate during hydrolysis. Cel7A and Cel7B cooperate synergistically, and synergism was approximately constant during the SPS hydrolysis. Thermal instability of the enzymes and product inhibition was not the main cause of reduced hydrolysis rates. Adding fresh substrate to substrate previously hydrolyzed for 24 h with Cel7A slightly increased the hydrolysis of SPS; however, the rate increased even more by adding fresh Cel7A. This suggests that enzymes become inactivated while adsorbed to the substrate and that unproductive binding is the main cause of hydrolysis rate reduction. The strongest increase in hydrolysis rate was achieved by adding Cel7B. An improved model is proposed that extends the standard endo-exo synergy model and explains the rapid decrease in hydrolysis rate. It appears that the processive action of Cel7A becomes hindered by obstacles in the lignocellulose substrate. Obstacles created by disordered cellulose chains can be removed by the endo activity of Cel7B, which explains some of the observed synergism between Cel7A and Cel7B. The improved model is supported by adsorption studies during hydrolysis.

Adsorption↗

PubMedDate not supplied

Initial characterization of ethyl(hydroxyethyl) cellulose using enzymic degradation and chromatographic methods.

Two different ethyl(hydroxyethyl) cellulose (EHEC) samples were characterized by size-exclusion chromatography (SEC) with multiangle light scattering (MALS) detection and high-performance anion-exchange chromatography (HPAEC) with pulsed amperometric detection (PAD). The aim of the study was to investigate the molar mass distribution and the heterogeneity of the substituent distribution, factors that are thought to affect the functional properties of EHEC. The presence of blocks of unsubstituted glucose units was studied by enzymic degradation of EHEC by two different endoglucanases from Trichoderma reesei. The SEC-MALS analysis of the hydrolysis products showed that both enzymes were strongly inhibited by the large number of substituents along the cellulose chain. However, as the weight-average molar mass was reduced from approximately 360,000 to 80,000 g/mol in one of the polymers and from 770,000 to 60,000 g/mol in the other polymer, it was suggested that both samples were composed of some unsubstituted regions where the enzymes got access to the glucosidic bonds. The amount of glucose released upon endoglucanase hydrolysis was determined by HPAEC-PAD, which gave information on the homogeneity of the substituent distribution. The production of unsubstituted glucose units indicated that one of the polymers had a more uneven distribution compared with the other. It was demonstrated that chemical characterization of EHEC is a complex task, which requires an analytical approach involving numerous different methods and techniques.

Cellulase↗

PubMedDate not supplied

Partitioning and characterization of tyrosine-tagged green fluorescent proteins in aqueous two-phase systems.

The green fluorescent protein GFPuv has been genetically engineered to investigate the influence of N-terminal tyrosine extensions in aqueous two-phase systems. Fusions in the N-terminus affected the protein expression, and tags containing three tyrosines and prolines influenced the expression favorably. This effect is probably due to changes in mRNA stability, because the amounts of corresponding mRNAs correlated with the amounts of GFPuv proteins. The partitioning was investigated in two different aqueous two-phase systems, a two-polymer system composed of EO30PO70/dextran and a PEG/salt system with potassium phosphate. Partitioning in the PEG/salt system generally was more favorable than in the EO30PO70/dextran system. Tags with three tyrosines resulted in higher partitioning toward the EO30PO70- and PEG-rich phases, respectively. The effect of adding proline residues to the tag was also investigated, and the partitioning effect of the tag was enhanced when prolines were included in the tags with three tyrosines. The best tyrosine tag, Y3P2, increased the partition coefficient 5 times in the PEG/salt system. Thermoseparation of the EO30PO70 phase allowed recovery of 83% Y3P2-GFPuv protein in a water phase.

Complex Mixtures↗