| 1. |
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| 2. |
- Carlsson, Karin, et al.
(författare)
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Site-directed fluorescence probing to dissect the calcium-dependent association between soluble tissue factor and factor VIIa domains
- 2003
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Ingår i: Biochimica et Biophysica Acta - Proteins and Proteomics. - 1570-9639 .- 1878-1454. ; 1648:1-2, s. 12-16
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Tidskriftsartikel (refereegranskat)abstract
- We have used the site-directed labeling approach to study the Ca 2+-dependent docking of factor VIIa (FVIIa) to soluble tissue factor (sTF). Nine Ca2+ binding sites are located in FVIIa and even though their contribution to the overall binding between TF and FVIIa has been thoroughly studied, their importance for local protein-protein interactions within the complex has not been determined. Specifically we have monitored the association of the ?-carboxyglutamic acid (Gla), the first EGF-like (EGF1), and the protease domains (PD) of FVIIa to sTF. Our results revealed that complex formation between sTF and FVIIa during Ca2+ titration is initiated upon Ca2+ binding to EGF1, the domain containing the site of highest Ca2+ affinity. Besides we showed that a Ca 2+-loaded Gla domain is required for an optimal association of all domains of FVIIa to sTF. Ca2+ binding to the PD seems to be of some importance for the docking of this domain to sTF. © 2003 Elsevier Science B.V. All rights reserved.
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| 3. |
- Chirica, Laura C., et al.
(författare)
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Expression and localization of α- and β-carbonic anhydrase in Helicobacter pylori
- 2002
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Ingår i: Biochimica et Biophysica Acta - Proteins and Proteomics. - 1570-9639 .- 1878-1454. ; 1601:2, s. 192-199
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Tidskriftsartikel (refereegranskat)abstract
- Helicobacter pylori, the causative agent of peptic ulcer disease, expresses two different forms of the zinc-containing enzyme carbonic anhydrase (CA) (α and β), catalyzing the reversible hydration of CO2. Presumably, the high CO2 requirement of H. pylori implies an important role for this enzyme in the bacterial physiology. In this paper, expression of the CAs has been analyzed in three different strains of the bacterium, 26695, J99 and 17.1, and appears to be independent of CO2 concentration in the investigated range (0.1–10%). Presence of the potent and highly specific CA inhibitor, acetazolamide, in the medium does not seem to inhibit bacterial growth at the given sulfonamide concentration. Moreover, the localization and distribution of the α-CA was analyzed by immunonegative staining, while SDS-digested freeze-fracture immunogold labelling was used for the β-form of the enzyme. The latter method has the advantage of allowing assessment of protein localization to distinct cell compartments and membrane structures. The resulting electron microscopy images indicate a localization of the β-CA in the cytosol, on the cytosolic side of the inner membrane and on the outer membrane facing the periplasmic space. The α-enzyme was found attached to the surface of the bacterium.
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| 4. |
- Lindholm, D, et al.
(författare)
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Neuronal apoptosis inhibitory protein : structural requirements for hippocalcin binding and effects on survival of NGF-denendent sympathetic neurons
- 2002
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Ingår i: Biochimica et Biophysica Acta - Proteins and Proteomics. - : ELSEVIER SCIENCE BV. - 1570-9639 .- 1878-1454. ; 1600:1-2, s. 138-147
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Tidskriftsartikel (refereegranskat)abstract
- Neuronal apoptosis inhibitory protein (NAIP) has been linked to the inherited disease, spinal muscular atrophy (SMA), which occurs in children with degeneration of the motorneurons. In the nervous system, NAIP is expressed by specific classes of neurons including spinal -motorneurons. Recently, NAIP was shown to interact with hippocalcin, which belongs to the neuronal calcium sensor (NCS) protein family. Here we-have studied this interaction in more detail, using deletions and a mutagenesis of the third baculovirus inhibitory repeat (BIR) motif in NAIP, and functional assays for neuronal death. The results showed that specific amino acids and the zinc finger domain in BIR3 are needed for efficient interaction of NAIP with hippocalcin. Cotransfections of NAIP-BIR3 and hippocalcin resulted in translocation and colocalisation of the two proteins in neuroblastoma cells. This was accompanied by an enhanced resistance towards cell death induced by high levels of calcium. In contrast, expression of NAIP-BIR3 and hippocalcin in sympathetic neurons did not protect against death induced by nerve growth factor (NGF) withdrawal. The results demonstrate a functional interaction of hippocalcin with NAIP-BIR3, which in neuroblastoma cells leads to rescue of cells after high intracellular calcium, but which in sympathetic neurons had no significant effect. The results indicate that NAIP in conjunction with hippocalcin can affect the survival of some, but not all neural cells, and this interaction may play a role in the neurodegenerative processes in SMA, and possible other human disorders. (C) 2002 Elsevier Science B.V All rights reserved.
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| 5. |
- Ghafouri, Bijar, 1972-, et al.
(författare)
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PLUNC in human nasal lavage fluid : multiple isoforms that bind to lipopolysaccharide
- 2004
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Ingår i: Biochimica et Biophysica Acta - Proteins and Proteomics. - 1570-9639 .- 1878-1454. ; 1699:1-2, s. 57-63
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Tidskriftsartikel (refereegranskat)abstract
- Here, we demonstrate the presence of multiple isoforms of palate lung nasal epithelial clone (PLUNC) in human nasal lavage fluid (NLF). Eight isoforms were separated by two-dimensional gel electrophoresis (2-DE), and peptide mapping of the proteins was performed using MALDI-TOF MS (matrix assisted laser desorption/ionization time of flight mass spectrometry) of tryptic and asparginase cleavages. The identification was verified by amino acid sequencing after analysis of collision-induced dissociation (CID) fragmentation spectra with nanoelectrospray MS/MS. One isoform showed an electrophoretic mobility shift after N-glycosidase treatment, indicating that at least one of the PLUNC isoforms is glycosylated. We also demonstrate that PLUNC in NLF binds to lipopolysaccharide (LPS) in vitro; indeed, out of all proteins present in NLF only the PLUNC isoforms were found to adsorb to an LPS-coated surface. These results show that PLUNC is expressed as multiple LPS-binding isoforms in human NLF. The possibility that PLUNC may play a role in the innate immune response of the upper airways is inferred.
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| 6. |
- Nilsson, Lisa O., et al.
(författare)
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Aromatic residues in the C-terminal region of glutathione transferase A1-1 influence rate-determining steps in the catalytic mechanism
- 2002
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Ingår i: Biochimica et Biophysica Acta - Proteins and Proteomics. - 1570-9639 .- 1878-1454. ; 1598:1-2, s. 199-205
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Tidskriftsartikel (refereegranskat)abstract
- Human glutathione transferase A1-1 (GST A1-1) has a flexible C-terminal segment that forms a helix (alpha9) closing the active site upon binding of glutathione and a small electrophilic substrate such as 1-chloro-2,4-dinitrobenzene (CDNB). In the absence of active-site ligands, the C-terminal segment is not fixed in one position and is not detectable in the crystal structure. A key residue in the alpha9-helix is Phe 220, which can interact with both the enzyme-bound glutathione and the second substrate, and possibly guide the reactants into the transition state. Mutation of Phe 220 into Ala and Thr was shown to reduce the catalytic efficiency of GST A1-1. The mutation of an additional residue, Phe 222, caused further decrease in activity. The presence of a viscosogen in the reaction medium decreased the kinetic parameters k(cat) and k(cat)/K(m) for the conjugation of CDNB catalyzed by wild-type GST A1-1, in agreement with the view that product release is rate limiting for the substrate-saturated enzyme. The mutations cause a decrease of the viscosity dependence of both kinetic parameters, indicating that the motion of the alpha9-helix is linked to catalysis in wild-type GST A1-1. The isomerization reaction with the alternative substrate Delta(5)-androstene-3,17-dione (AD) is affected in a similar manner by the viscosogens. The transition state energy of the isomerization reaction, like that of the CDNB conjugation, is lowered by Phe 220 as indicated by the effects of the mutations on k(cat)/K(m). The results demonstrate that Phe 220 and Phe 222, in the dynamic C-terminal segment, influence rate-determining steps in the catalytic mechanism of both the substitution and the isomerization reactions.
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| 7. |
- Nilsson, Anna, et al.
(författare)
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Partitioning of peptide-tagged proteins in aqueous two-phase systems using hydrophobically modified micelle-forming thermoseparating polymer
- 2002
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Ingår i: Biochimica et Biophysica Acta - Proteins and Proteomics. - 1570-9639. ; 1601:2, s. 138-148
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Tidskriftsartikel (refereegranskat)abstract
- 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 (C14H29) at both ends. The HM-EOPO polymer is strongly self-associating and has a lower critical solution temperature (cloud point) at 12oC 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.
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| 8. |
- Nilsson, Anna, et al.
(författare)
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Tryptophan-tagged cutinase studied by steady state fluorescence for understanding of tag interactions in aqueous two-phase systems
- 2003
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Ingår i: Biochimica et Biophysica Acta - Proteins and Proteomics. - 1570-9639. ; 1646:1-2, s. 57-66
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Tidskriftsartikel (refereegranskat)abstract
- Genetic engineering has been used to construct fusion proteins of Fusarium solani pisi cutinase and tryptophan-based tags, expressed in Saccharomyces cerevisiae, to increase the partitioning in aqueous two-phase systems. The separation systems were composed of thermoseparating polymers (random copolymers of ethylene oxide and propylene oxide, EOPO) and detergents (C12EOn). In this study, the fluorescence behaviour of the peptide-tagged protein, free peptide tag and tryptophan was investigated. The tryptophan-tagged proteins, cutinase-(WP)4 and cutinase-TGGSGG-(WP)4, showed emission spectra similar to the free peptides and tryptophan, indicating solvent exposure of the tag. The influence of polymers and detergents on the fluorescence of tagged proteins was examined. When peptides and tagged proteins were exposed to polymer, a slight blue shift of the emission maximum was observed. Larger blue shifts of the emission maximum were observed when C12EOn detergents were utilised. The results correlate with aqueous two-phase partitioning where addition of C12EOn detergents results in more extreme partitioning compared to systems containing only polymers. Dynamic light scattering (DLS) measurements of the EOPO copolymers were carried out, showing that the polymers did not aggregate at concentrations used in aqueous two-phase systems. Quenching of fluorescence with iodide for both proteins and peptide tags was studied. Plots according to the Stern-Volmer equation resulted in a linear fit, indicating exposed tryptophan residues for both free peptides and fusion proteins. The quenching constants were similar for both tagged protein and free peptide tag. The fluorescence results indicated that the tryptophan residues in the tag were exposed to the solvent and could interact with detergents and polymers in the two-phase systems.
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| 9. |
- Salis, A, et al.
(författare)
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The atypical lipase B from Candida antarctica is better adapted for organic media than the typical lipase from Thermomyces lanuginosa.
- 2003
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Ingår i: Biochimica et Biophysica Acta - Proteins and Proteomics. - 1570-9639. ; 1646:1-2, s. 145-151
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Tidskriftsartikel (refereegranskat)abstract
- Candida antarctica lipase B (CALB) and Thermomyces lanuginosa lipase (TLL) were evaluated as catalysts in different reaction media using hydrolysis of tributyrin as model reaction. In o/w emulsions, the enzymes were used in the free form and for use in monophasic organic media, the lipases were adsorbed on porous polypropylene (Accurel EP-100). In monophasic organic media, the highest specific activity of both lipases was obtained in pure tributyrin at a water activity of >0.5 and at an enzyme loading of 10 mg/g support. With tributyrin emulsified in water, the specific activities were 2780 mol min−1 mg−1 for TLL and 535 mol min−1 mg−1 for CALB. Under optimal conditions in pure tributyrin, CALB expressed 49% of the activity in emulsion (264 mol min−1 mg−1) while TLL expressed only 9.2% (256 mol min−1 mg−1) of its activity in emulsion. This large decrease is probably due to the structure of TLL, which is a typical lipase with a large lid domain. Conversion between open and closed conformers of TLL involves large internal movements and catalysis probably requires more protein mobility in TLL than in CALB, which does not have a typical lid region. Furthermore, TLL lost more activity than CALB when the water activity was reduced below 0.5, which could be due to further reduction in protein mobility.
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| 10. |
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