| 1. |
- Fa, M, et al.
(author)
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Conformational studies of plasminogen activator inhibitor type 1 by fluorescence spectroscopy. Analysis of the reactive centre of inhibitory and substrate forms, and of their respective reactive-centre cleaved forms.
- 2000
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In: European Journal of Biochemistry. - : Wiley. - 0014-2956 .- 1432-1033. ; 267:12, s. 3729-34
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Journal article (peer-reviewed)abstract
- The inhibitors that belong to the serpin family are suicide inhibitors that control the major proteolytic cascades in eucaryotes. Recent data suggest that serpin inhibition involves reactive centre cleavage followed by loop insertion, whereby the covalently linked protease is translocated away from the initial docking site. However under certain circumstances, serpins can also be cleaved like a substrate by target proteases. In this report we have studied the conformation of the reactive centre of plasminogen activator inhibitor type 1 (PAI-1) mutants with inhibitory and substrate properties. The polarized steady-state and time-resolved fluorescence anisotropies were determined for BODIPY(R) probes attached to the P1' and P3 positions of the substrate and active forms of PAI-1. The fluorescence data suggest an extended orientational freedom of the probe in the reactive centre of the substrate form as compared to the active form, revealing that the conformation of the reactive centres differ. The intramolecular distance between the P1' and P3 residues in reactive centre cleaved inhibitory and substrate mutants of PAI-1, were determined by using the donor-donor energy migration (DDEM) method. The distances found were 57+/-4 A and 63+/-3 A, respectively, which is comparable to the distance obtained between the same residues when PAI-1 is in complex with urokinase-type plasminogen activator (uPA). Following reactive centre cleavage, our data suggest that the core of the inhibitory and substrate forms possesses an inherited ability of fully inserting the reactive centre loop into beta-sheet A. In the inhibitory forms of PAI-1 forming serpin-protease complexes, this ability leads to a translocation of the cognate protease from one pole of the inhibitor to the opposite one.
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| 2. |
- Burghart, Armin, et al.
(author)
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Energy transfer cassettes based on BODIPY® dyes
- 2000
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In: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; :2203-4
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Journal article (peer-reviewed)abstract
- The donor–acceptor dye cassettes 1–4 were designed to capture energy at a single wavelength and to convert it to well-resolved, intense fluorescence emissions; in practice, Stokes shifts of 40–148 nm, quantum yields of 0.12–0.60, and efficient energy transfer was demonstrated.
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| 3. |
- Edman, Peter, et al.
(author)
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Extended Förster theory of donor-donor energy migration in bifluorophoric macromolecules. Part II : Method for determining intramolecular distances with experimental validation using mono and bifluorophoric systems
- 2000
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In: Physical chemistry chemical physics. ; 2:12, s. 2795-2801
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Journal article (peer-reviewed)abstract
- Recently an approximate theory was presented and applied for determining intramolecular distances in proteins. The rate of donor-donor energy migration (DDEM) is extracted and analysed from fluorescence depolarisation experiments by means of the DDEM model (Karolin et al., Biophys. J., 1998, 74, 11; Bergström et al., Proc. Natl. Acad. Sci., 1999, 96, 12477). Previously an extended Förster theory (EFT) was derived (Johansson et al., J. Chem. Phys., 1996, 105, 10896), which accounts for DDEM between reorienting molecules. For the first time, this rigorous theory is applied for analysing time-resolved fluorescence depolarisation data, accumulated by using the time-correlated single photon counting (TCSPC) technique. A simulation-deconvolution algorithm is presented which reduces the need of the DDEM model (Edman et al., Phys. Chem. Chem. Phys., 2000, 2, 1789), and other approximate theories (Edman et al., Mol. Phys., submitted). Two bifluorophoric systems were studied, namely; 1,32-dihydroxy-dotriacontane-bis(rhodamine) 101 ester solubilised in lipid vesicles, and bis(9-anthrylmethyl-phosphonate) bisteroid dissolved in propane-1,2-diol. The bis-rhodamine molecules span across lipid bilayers, so that the two rhodamine moieties of the molecule are localised on opposite sides of a bilayer. From the analyses of the fluorescence anisotropy, the donor-donor distances were determined to be 36.5 ± 1 and 21.0 ± 1.5 Å, for the membrane spanning molecule and the bisteroid, respectively. The results are in good agreement with independent studies.
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| 4. |
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| 5. |
- Edman, Peter, et al.
(author)
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On determining intramolecular distances from donor–donor energy migration (DDEM) within bifluorophoric macromolecules
- 2000
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In: PHYSICAL CHEMISTRY CHEMICAL PHYSICS. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 2, s. 1789-94
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Journal article (peer-reviewed)abstract
- Recently a model based on donor–donor energy migration (DDEM) was developed for examining structure–function properties of biomacromolecules such as proteins (J. Chem. Soc., Faraday Trans., 1996, 92, 1563). Unlike the extended Förster theory (EFT; J. Chem. Phys., 1996, 105, 10896) the DDEM model is straightforward to apply in the analyses of fluorescence depolarisation experiments, as obtained by the time-correlated single photon counting (TCSPC) technique. In order to test the validity of the DDEM model, the EFT was used to create synthetic depolarisation data. These mimic true TCSPC experiments and cover a wide range of physical conditions, which are difficult to arrange for in real experiments with model systems. In particular, the relative rate of DDEM () and the rotation correlation time () of the donor molecules was examined. The DDEM rates obtained from the analyses were compared to the true rates. From these results the relative error of the intramolecular distances were calculated. For values 1<12<25, the DDEM model is slightly overestimating the distances. Typically, the distances determined with the DDEM model are overestimated by 5–10%.
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| 6. |
- Fa, Ming, et al.
(author)
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The structure of a serpin–protease complex revealed by intramolecular distance measurements using donor–donor energy migration and mapping of interaction sites
- 2000
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In: Structure. ; 8:4, s. 397-405
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Journal article (peer-reviewed)abstract
- Background: The inhibitors that belong to the serpin family are widely distributed regulatory molecules that include most protease inhibitors found in blood. It is generally thought that serpin inhibition involves reactive-centre cleavage, loop insertion and protease translocation, but different models of the serpin–protease complex have been proposed. In the absence of a spatial structure of a serpin–protease complex, a detailed understanding of serpin inhibition and the character of the virtually irreversible complex have remained controversial.Results: We used a recently developed method for making precise distance measurements, based on donor–donor energy migration (DDEM), to accurately triangulate the position of the protease urokinase-type plasminogen activator (uPA) in complex with the serpin plasminogen activator inhibitor type 1 (PAI-1). The distances from residue 344 (P3) in the reactive-centre loop of PAI-1 to residues 185, 266, 313 and 347 (P1′) were determined. Modelling of the complex using this distance information unequivocally placed residue 344 in a position at the distal end from the initial docking site with the reactive-centre loop fully inserted into β sheet A. To validate the model, seven single cysteine substitution mutants of PAI-1 were used to map sites of protease–inhibitor interaction by fluorescence depolarisation measurements of fluorophores attached to these residues and cross-linking using a sulphydryl-specific cross-linker.Conclusions: The data clearly demonstrate that serpin inhibition involves reactive-centre cleavage followed by full-loop insertion whereby the covalently linked protease is translocated from one pole of the inhibitor to the opposite one.
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