| 1. |
- Wu, Min, 1986, et al.
(författare)
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Proline 411 biases the conformation of the intrinsically disordered plant UVR8 photoreceptor C27 domain altering the functional properties of the peptide
- 2019
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- UVR8 (UV RESISTANCE LOCUS 8) is a UV-B photoreceptor responsible for initiating UV-B signalling in plants. UVR8 is a homodimer in its signalling inactive form. Upon absorption of UV radiation, the protein monomerizes into its photoactivated state. In the monomeric form, UVR8 binds the E3 ubiquitin ligase COP1 (CONSTITUTIVELY PHOTOMORPHOGENIC 1), triggering subsequent UV-B-dependent photomorphogenic development in plants. Recent in vivo experiments have shown that the UVR8 C-terminal region (aa 397-423; UVR8(C27)) alone is sufficient to regulate the activity of COP1. In this work, CD spectroscopy and NMR experiments showed that the UVR8(C27) domain was non-structured but gained secondary structure at higher temperatures leading to increased order. Bias-exchange metadynamics simulations were also performed to evaluate the free energy landscape of UVR8(C27). An inverted free energy landscape was revealed, with a disordered structure in the global energy minimum. Flanking the global energy minimum, more structured states were found at higher energies. Furthermore, stabilization of the low energy disordered state was attributed to a proline residue, P411, as evident from P411A mutant data. P411 is also a key residue in UVR8 binding to COP1. UVR8(C27) is therefore structurally competent to function as a molecular switch for interaction of UVR8 with different binding partners since at higher free energies different structural conformations are being induced in this peptide. P411 has a key role for this function.
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| 2. |
- Eriksson, Leif A., 1964-, et al.
(författare)
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Tetrazole derivatives as cytochrome p450 inhibitors
- 2019
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Patent (populärvet., debatt m.m.)abstract
- According to the invention there is provided a compound of formula I, wherein R1 and R2 have meanings given in the description, which compounds are useful in the treatment of skin disorders and other diseases.
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| 3. |
- Czegeny, G., et al.
(författare)
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Hydrogen peroxide contributes to the ultraviolet-B (280-315 nm) induced oxidative stress of plant leaves through multiple pathways
- 2014
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Ingår i: Febs Letters. - : Wiley. - 0014-5793 .- 1873-3468. ; 588:14, s. 2255-2261
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Tidskriftsartikel (refereegranskat)abstract
- Solar UV-B (280-315 nm) radiation is a developmental signal in plants but may also cause oxidative stress when combined with other environmental factors. Using computer modeling and in solution experiments we show that UV-B is capable of photosensitizing hydroxyl radical production from hydrogen peroxide. We present evidence that the oxidative effect of UV-B in leaves is at least twofold: (i) it increases cellular hydrogen peroxide concentrations, to a larger extent in pyridoxine antioxidant mutant pdx1.3-1 Arabidopsis and; (ii) is capable of a partial photo-conversion of both 'natural' and 'extra' hydrogen peroxide to hydroxyl radicals. As stress conditions other than UV can increase cellular hydrogen peroxide levels, synergistic deleterious effects of various stresses may be expected already under ambient solar UV-B. (C) 2014 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.
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| 4. |
- Albet-Torres, Nuria, et al.
(författare)
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Molecular motors on lipid bilayers and silicon dioxide: different driving forces for adsorption
- 2010
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Ingår i: Soft Matter. - : Royal Society of Chemistry (RSC). - 1744-6848 .- 1744-683X. ; 6:14, s. 3211-3219
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Tidskriftsartikel (refereegranskat)abstract
- Understanding how different types of interactions govern adsorption of the myosin motor fragment heavy meromyosin (HMM) onto different substrates is important in functional studies of actomyosin and for the development of motor powered lab-on-a-chip applications. In this study, we have combined in vitro motility assays and quartz crystal microbalance with dissipation (QCM-D) monitoring to investigate the underlying adsorption mechanisms of HMM onto supported lipid bilayers in comparison with pure and silanized SiO2. The QCM-D results, combined with data showing actin transportation by HMM adsorbed onto positively charged supported lipid bilayers, suggest reversible HMM surface adsorption via the negatively charged coiled-coil tail region. In contrast, the QCM-D data for HMM adsorption onto negatively charged lipids support a model according to which HMM adsorbs onto negatively charged surfaces largely via the positively charged actin binding regions. Adsorption studies at low (30-65 mM) and high (185-245 mM) ionic strengths onto piranha cleaned SiO2 surfaces (contact angle
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| 5. |
- Persson, Malin, 1983-, et al.
(författare)
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Heavy Meromyosin Molecules Extending More Than 50 nm above Adsorbing Electronegative Surfaces
- 2010
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 1520-5827 .- 0743-7463. ; 26:12, s. 9927-9936
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Tidskriftsartikel (refereegranskat)abstract
- In the in vitro motility assay, actin filaments are propelled by surface-adsorbed myosin motors, or rather, myosin motor fragments such as heavy meromyosin (HMM). Recently, efforts have been made to develop actomyosin powered nanodevices on the basis of this assay but such developments are hampered by limited understanding of the HMM adsorption geometry. Therefore, we here investigate the HMM adsorption geometries on trimethylchlorosilane-[TMCS-] derivatized hydrophobic surfaces and on hydrophilic negatively charged surfaces (SiO2). The TMCS surface is of great relevance in fundamental studies of actomyosin and both surface substrates are important for the development of motor powered nanodevices. Whereas both the TMCS and SiO2 surfaces were nearly saturated with HMM (incubation at 120 mu g mL(-1)) there was little actin binding on SiO2 in the absence of ATP and no filament sliding in the presence of ATP. This contrasts with excellent actin-binding and motility on TMCS. Quartz crystal microbalance with dissipation (QCM-D) studies demonstrate a HMM layer with substantial protein mass up to 40 nm above the TMCS surface, considerably more than observed for myosin subfragment 1 (SI; 6 nm). Together with the excellent actin transportation on TMCS, this strongly suggests that HMM adsorbs to TMCS mainly via its most C-terminal tail part. Consistent with this idea, fluorescence interference contrast (FLIC) microscopy showed that actin filaments are held by HMM 38 +/- 2 nm above the TMCS-surface with the catalytic site, on averge, 20-30 nm above the surface. Viewed in a context with FLIC, QCM-D and TIRF results, the lack of actin motility and the limited actin binding on SiO2 shows that HMM adsorbs largely via the actin-binding region on this surface with the C-terminal coiled-coil tails extending > 50 nm into solution. The results and new insights from this study are of value, not only for the development of motor powered nanodevices but also for the interpretation of fundamental biophysical studies of actomyosin function and for the understanding of surface protein interactions in general.
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| 6. |
- Persson, Malin, et al.
(författare)
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Nonlinear Cross-Bridge Elasticity and Post-Power-Stroke Events in Fast Skeletal Muscle Actomyosin
- 2013
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Ingår i: Biophysical Journal. - : Elsevier BV. - 0006-3495 .- 1542-0086. ; 105:8, s. 1871-1881
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Tidskriftsartikel (refereegranskat)abstract
- Generation-of force and movement by actomyosin cross-bridges is the molecular basis of muscle contraction, but generally accepted ideas about cross-bridge properties have recently been questioned. Of the utmost significance, evidence for nonlinear cross-bridge elasticity has been presented. We here investigate how this and other newly discovered or postulated phenomena would modify cross-bridge operation, with focus on post-power-stroke events. First, as an experimental basis, we present evidence for a hyperbolic [MgATP]-velocity relationship of heavy-meromyosin-propelled actin filaments in the in vitro motility assay using fast rabbit skeletal muscle myosin (28-29 degrees C). As the hyperbolic [MgATP]-velocity relationship was not consistent with interhead cooperativity, we developed a cross-bridge model with independent myosin heads and strain-dependent interstate transition rates. The model, implemented with inclusion of MgATP-independent detachment from the rigor state, as suggested by previous single-molecule mechanics experiments, accounts well for the [MgATP]-velocity relationship if nonlinear cross-bridge elasticity is assumed, but not if linear cross-bridge elasticity is assumed. In addition, a better fit is obtained with load-independent than with load-dependent MgATP-induced detachment rate. We discuss our results in relation to previous data showing a nonhyperbolic [MgATP1-velocity relationship when actin filaments are propelled by myosin subfragment 1 or full-length myosin. We also consider the implications of our results for characterization of the cross-bridge elasticity in the filament lattice of muscle.
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| 7. |
- Bengtsson, Elina, et al.
(författare)
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Analysis of Flexural Rigidity of Actin Filaments Propelled by Surface Adsorbed Myosin Motors
- 2013
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Ingår i: Cytoskeleton. - : John Wiley & Sons. - 1949-3584 .- 1949-3592. ; 70:11, s. 718-728
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Tidskriftsartikel (refereegranskat)abstract
- Actin filaments are central components of the cytoskeleton and the contractile machinery of muscle. The filaments are known to exist in a range of conformational states presumably with different flexural rigidity and thereby different persistence lengths. Our results analyze the approaches proposed previously to measure the persistence length from the statistics of the winding paths of actin filaments that are propelled by surface-adsorbed myosin motor fragments in the in vitro motility assay. Our results suggest that the persistence length of heavy meromyosin propelled actin filaments can be estimated with high accuracy and reproducibility using this approach provided that: (1) the in vitro motility assay experiments are designed to prevent bias in filament sliding directions, (2) at least 200 independent filament paths are studied, (3) the ratio between the sliding distance between measurements and the camera pixel-size is between 4 and 12, (4) the sliding distances between measurements is less than 50% of the expected persistence length, and (5) an appropriate cut-off value is chosen to exclude abrupt large angular changes in sliding direction that are complications, e.g., due to the presence of rigor heads. If the above precautions are taken the described method should be a useful routine part of in vitro motility assays thus expanding the amount of information to be gained from these.
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| 8. |
- Hansson Mild, Kjell, 1942-, et al.
(författare)
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ELF noise fields : a review
- 2010
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Ingår i: Electromagnetic Biology and Medicine. - : Informa Healthcare. - 1536-8378 .- 1536-8386. ; 29:3, s. 72-97
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Tidskriftsartikel (refereegranskat)abstract
- The debate as to whether low-level electromagnetic fields can affect biological systems and in the long term cause health effects has been going on for a long time. Yet the interaction of weak electromagnetic fields (EMF) with living cells, undoubtedly a most important phenomenon, is still not well understood. The exact mechanisms by which the effects are produced have not been identified. Furthermore, it is not possible to clearly define which aspects of an EMF exposure that constitute the "dose." One of the groups that contributed to solving this problem is the Bioelectromagnetics group at Catholic University of America (CUA), Washington, D. C. Their work has been devoted to investigating the physical parameters that are needed to obtain an effect of EMF exposure on biological systems, and also how to inhibit the effect. This is a review of their work on bioeffects caused by low-level EMF, their dependence on coherence time, constancy, spatial averaging, and also how the effects can be modified by an applied ELF noise magnetic field. The group has been using early chick embryos, and L929 and Daudi cells as their main experimental systems. The review also covers the work of other groups on low-level effects and the inhibition of the effects with an applied noise field. The group at CUA has shown that biological effects can be found after exposure to low-level ELF and RF electromagnetic fields, and when effects are observed, applying an ELF magnetic noise field inhibits the effects. Also, other research groups have tried to replicate the studies from the CUA group, or to apply EMF noise to suppress EMF-induced effects. Replications of the CUA effects have not always been successful. However, in all cases where the noise field has been applied to prevent an observed effect, it has been successful in eliminating the effect.
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| 9. |
- Jass, Jana, et al.
(författare)
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Physical properties of Escherichia coli P pili measured by optical tweezers
- 2004
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Ingår i: Biophysical Journal. - : Elsevier BV. - 0006-3495 .- 1542-0086. ; 87:6, s. 4271-4283
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Tidskriftsartikel (refereegranskat)abstract
- The mechanical behavior of individual P pili of uropathogenic Escherichia coli has been investigated using optical tweezers. P pili, whose main part constitutes the PapA rod, composed of approximately 10(3) PapA subunits in a helical arrangement, are distributed over the bacterial surface and mediate adhesion to host cells. They are particularly important in the pathogenesis of E. coli colonizing the upper urinary tract and kidneys. A biological model system has been established for in situ measurements of the forces that occur during mechanical stretching of pili. A mathematical model of the force-versus-elongation behavior of an individual pilus has been developed. Three elongation regions of pili were identified. In region I, P pili stretch elastically, up to a relative elongation of 16 +/- 3%. The product of elasticity modulus and area of a P pilus, EA, was assessed to 154 +/- 20 pN (n=6). In region II, the quaternary structure of the PapA rod unfolds under a constant force of 27 +/- 2 pN (n approximately 100) by a sequential breaking of the interactions between adjacent layers of PapA subunits. This unfolding can elongate the pilus up to 7 +/- 2 times. In region III, pili elongate in a nonlinear manner as a result of stretching until the bond ruptures.
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| 10. |
- van Zalinge, Harm, et al.
(författare)
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Actin Filament Motility Induced Variation of Resonance Frequency and Rigidity of Polymer Surfaces Studied by Quartz Crystal Microbalance
- 2012
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 28:42, s. 15033-15037
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Tidskriftsartikel (refereegranskat)abstract
- This contribution reports on the quantification of the parameters of the motility assays for actomyosin system using a quartz crystal microbalance (QCM). In particular, we report on the difference in the observed resonance frequency and dissipation of a quartz crystal when actin filaments are stationary as opposed to when they are motile. The changes in QCM measurements were studied for various polymer-coated surfaces functionalized with heavy meromyosin (HMM). The results of the QCM experiments show that the HMM-induced sliding velocity of actin filaments is modulated by a combination of the viscoelastic properties of the polymer layer including the HMM motors.
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