| 1. |
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| 2. |
- Cheng, Kimberley, et al.
(författare)
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Rapana thomasiana hemocyanin (RtH): Comparison of the two isoforms, RtH1 and RtH2, at 19 angstrom 16 angstrom resolution
- 2006
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Ingår i: Micron. - : Elsevier BV. - 0968-4328 .- 1878-4291. ; 37:6, s. 566-576
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Forskningsöversikt (refereegranskat)abstract
- Three-dimensional (3D) reconstructions of the two 8.4 MDa Rapana thomasiana hemocyanin isoforms, RtH1 and RtH2, have been obtained by cryoelectron microscopy of molecules embedded in vitreous ice and single particle image processing. The final 3D structures of the RtH1 and RtH2 didecamers at 19 angstrom and 16 angstrom resolution, respectively, are very similar to earlier reconstructions of gastropodan hemocyanins, revealing structural features such as the obliquely oriented subunits, the five- and two-fold symmetrical axes. Three new interactions are defined; two of them connecting the arch and the wall while the third is formed between the collar and the wall. The collar-wall connection and one of the arch-wall connections are positioned between two individual subunit dimers, while the second arch-wall connection is located between two subunits within the subunit dimer. All three interactions establish connections to the first tier of the wall. Furthermore, for each interaction we have allocated two first tier functional units most likely involved in forming the connections. (
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| 3. |
- Elmlund, Hans, et al.
(författare)
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A new cryo-EM single-particle Ab initio reconstruction method visualizes secondary structure elements in an ATP-Fueled AAA+ motor
- 2008
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Ingår i: Journal of Molecular Biology. - : Elsevier BV. - 1089-8638 .- 0022-2836. ; 375:4, s. 934-947
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Tidskriftsartikel (refereegranskat)abstract
- The generation of ab initio three-dimensional (3D) models is a bottleneck in the studies of large macromolecular assemblies by single-particle cryo-electron microscopy. We describe here a novel method, in which established methods for two-dimensional image processing are combined with newly developed programs for joint rotational 3D alignment of a large number of class averages (RAD) and calculation of 3D volumes from aligned projections (VolRec). We demonstrate the power of the method by reconstructing an 660-kDa ATP-fueled AAA+ motor to 7.5 Å resolution, with secondary structure elements identified throughout the structure. We propose the method as a generally applicable automated strategy to obtain 3D reconstructions from unstained single particles imaged in vitreous ice.
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| 4. |
- Elmlund, Hans, et al.
(författare)
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Cryo-EM Reveals Promoter DNA Binding and Conformational Flexibility of the General Transcription Factor TFIID
- 2009
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Ingår i: Structure. - : Elsevier BV. - 0969-2126 .- 1878-4186. ; 17:11, s. 1442-1452
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Tidskriftsartikel (refereegranskat)abstract
- The general transcription factor IID (TFIID) is required for initiation of RNA polymerase II-dependent transcription at many eukaryotic promoters. TFIID comprises the TATA-binding protein (TBP) and several conserved TBP-associated factors (TAFs). Recognition of the core promoter by TFIID assists assembly of the preinitiation complex. Using cryo-electron microscopy in combination with methods for ab initio single-particle reconstruction and heterogeneity analysis, we have produced density maps of two conformational states of Schizosaccharomyces pombe TFIID, containing and lacking TBP. We report that TBP-binding is coupled to a massive histone-fold domain rearrangement. Moreover, docking of the TBP-TAF1(N-terminus) atomic structure to the THID map and reconstruction of a TAF-promoter DNA complex helps to account for TAF-dependent regulation of promoter-TBP and promoter-TAF interactions.
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| 5. |
- Elmlund, Hans, 1978-
(författare)
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Protein structure dynamics and interplay : by single-particle electron microscopy
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Single-particle cryo-electron microscopy (cryo-EM) is a method capable of obtaining information about the structural organization and dynamics of large macromolecular assemblies. In the late nineties, the method was suggested to have the potential of generating “atomic resolution” reconstructions of particles above a certain mass. However, visualization of secondary structure elements in cryo-EM reconstructions has so far been achieved mainly for highly symmetrical macromolecular assemblies or by using previously existing X-ray structures to solve the initial alignment problem. A factor that severely limits the resolution for low-symmetry (point group symmetry Cn) particles is the problem of ab initio three-dimensional alignment of cryo-EM projection images of proteins in vitreous ice. A more general problem in the field of molecular biology is the study of heterogeneous structural properties of particles in preparations of purified macromolecular complexes. If not resolved, structural heterogeneity limits the achievable resolution of a cryo-EM reconstruction and makes correct biological interpretation difficult. If resolved, the heterogeneity instead offers a tremendous biological insight into the dynamic behaviour of a structure, and statistical information about partitioning over subpopulations with distinct structural features within the ensemble of particles may be gained. This thesis adds to the existing body of methods in the field of single-particle cryo-EM by addressing the problem of ab initio rotational alignment and the problem of resolving structural heterogeneity without using a priori information about the structural variability within large populations of cryo-EM projections of unstained proteins. The thesis aims at making the single-particle cryo-EM method a generally applicable tool for generating subnanometer resolution reconstructions and perform heterogeneity analysis of biological macromolecules.
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| 6. |
- Elmlund, Hans, et al.
(författare)
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The cyclin-dependent kinase 8 module sterically blocks Mediator interactions with RNA polymerase II
- 2006
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 103:43, s. 15788-15793
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Tidskriftsartikel (refereegranskat)abstract
- CDK8 (cyclin-dependent kinase 8), along with CycC, Med12, and Med13, form a repressive module (the Cdk8 module) that prevents RNA polymerase II (pol II) interactions with Mediator. Here, we report that the ability of the Cdk8 module to prevent pol II interactions is independent of the Cdk8-dependent kinase activity. We use electron microscopy and single-particle reconstruction to demonstrate that the Cdk8 module forms a distinct structural entity that binds to the head and middle region of Mediator, thereby sterically blocking interactions with pol II.
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| 7. |
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| 8. |
- Kronqvist, Nina, et al.
(författare)
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Efficient protein production inspired by how spiders make silk
- 2017
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Ingår i: Nature Communications. - : Nature Publishing Group. - 2041-1723. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Membrane proteins are targets of most available pharmaceuticals, but they are difficult to produce recombinantly, like many other aggregation-prone proteins. Spiders can produce silk proteins at huge concentrations by sequestering their aggregation-prone regions in micellar structures, where the very soluble N-terminal domain (NT) forms the shell. We hypothesize that fusion to NT could similarly solubilize non-spidroin proteins, and design a charge-reversed mutant (NT star) that is pH insensitive, stabilized and hypersoluble compared to wildtype NT. NT star-transmembrane protein fusions yield up to eight times more of soluble protein in Escherichia coli than fusions with several conventional tags. NT star enables transmembrane peptide purification to homogeneity without chromatography and manufacture of low-cost synthetic lung surfactant that works in an animal model of respiratory disease. NT star also allows efficient expression and purification of non-transmembrane proteins, which are otherwise refractory to recombinant production, and offers a new tool for reluctant proteins in general.
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| 9. |
- Lundqvist, Joakim, et al.
(författare)
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ATP-Induced Conformational Dynamics in the AAA plus Motor Unit of Magnesium Chelatase
- 2010
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Ingår i: Structure. - : Elsevier BV. - 0969-2126 .- 1878-4186. ; 18:3, s. 354-365
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Tidskriftsartikel (refereegranskat)abstract
- Mg-chelatase catalyzes the first committed step of the chlorophyll biosynthetic pathway, the ATP-dependent insertion of Mg2+ into protoporphyrin IX (PPIX). Here we report the reconstruction using single-particle cryo-electron microscopy of the complex between subunits BchD and BchI of Rhodobacter capsulatus Mg-chelatase in the presence of ADP, the nonhydrolyzable ATP analog AMPPNP, and ATP at 7.5 angstrom, 14 angstrom, and 13 angstrom resolution, respectively. We show that the two AAA+ modules of the subunits form a unique complex of 3 dimers related by a three-fold axis. The reconstructions demonstrate substantial differences between the conformations of the complex in the presence of ATIP and ADP, and suggest that the C-terminal integrin-I domains of the BchD subunits play a central role in transmitting conformational changes of BchI to BchD. Based on these data a model for the function of magnesium chelatase is proposed.
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| 10. |
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| 11. |
- Schagerlöf, Ulrika, et al.
(författare)
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Structural basis of the iron storage function of frataxin from single-particle reconstruction of the iron-loaded oligomer
- 2008
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Ingår i: Biochemistry. - : American Chemical Society (ACS). - 0006-2960 .- 1520-4995. ; 47:17, s. 4948-4954
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Tidskriftsartikel (refereegranskat)abstract
- The mitochondrial protein frataxin plays a central role in mitochondrial iron homeostasis, and frataxin deficiency is responsible for Friedreich ataxia, a neurodegenerative and cardiac disease that affects 1 in 40000 children. Here we present a single-particle reconstruction from cryoelectron microscopic images of iron-loaded 24-subunit oligomeric frataxin particles at 13 and 17 angstrom resolution. Computer-aided classification of particle images showed heterogeneity in particle size, which was hypothesized to result from gradual accumulation of iron within the core structure. Thus, two reconstructions were created from two classes of particles with iron cores of different sizes. The reconstructions show the iron core of frataxin for the first time. Compared to the previous reconstruction of iron-free particles from negatively stained images, the higher resolution of the present reconstruction allowed a more reliable analysis of the overall three-dimensional structure of the 24-meric assembly. This was done after docking the X-ray structure of the frataxin trimer into the EM reconstruction. The structure revealed a close proximity of the suggested ferroxidation sites of different monomers to the site proposed to serve in iron nucleation and mineralization. The model also assigns a new role to the N-terminal helix of frataxin in controlling the channel at the 4-fold axis of the 24-subunit oligomer. The reconstructions show that, together with some common features, frataxin has several unique features which distinguish it from ferritin. These include the overall organization of the oligomers, the way they are stabilized, and the mechanisms of iron core nucleation.
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| 12. |
- von Holst, Hans, et al.
(författare)
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White Shark Protein Metabolism may be a Model to Improve the Outcome of Cytotoxic Brain Tissue Edema and Cognitive Deficiency after Traumatic Brain Injury and Stroke
- 2018
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Ingår i: Journal of Neurology and Neurobiology. - : Sci Forschen, Inc.. - 2379-7150. ; 4:2
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Tidskriftsartikel (refereegranskat)abstract
- Increased intracellular water content defined as cytotoxic brain tissue edema is a serious secondary clinical complication to traumatic brain injury (TBI) and stroke and without knowledge to the etiology. Recently a hypothesis to the nervous tissue edema was presented suggesting that external dynamic and internal mechanical static impact forces caused protein unfolding resulting in an increased brain tissue water content. The hypothesis was confirmed by computer simulation tests. In this laboratory study we further evaluated the hypothesis by using the mature protein laminin LN521 upon the effects of both dynamic as well as static impact forces, respectively. Laminin was chosen as a representative protein due to it´s general and abundance presence in the cells. The treated laminin solutions were then analyzed with denatured electrophoresis and Electron Microscopy showing aggregation and fragmentation of the laminin structures. The present results confirm earlier hypothesis and computer simulation suggesting for the first time that dynamic impact force in an accident and increased mechanical static force in stroke unfold mature proteins having the potential to increase the intracellular water content defined as cytotoxic brain tissue edema. The clinical condition resembles the phenomenon when elasmobranchs including white sharks prevent their cells from too high hydrostatic pressure in the deep sea. Thus, the present laboratory study results and knowledge from marine physics may be considered to improve the clinical treatment and outcome of TBI and stroke patients.
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| 13. |
- Ambort, Daniel, 1978, et al.
(författare)
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Calcium and pH-dependent packing and release of the gel-forming MUC2 mucin.
- 2012
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 1091-6490 .- 0027-8424. ; 109:15, s. 5645-50
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Tidskriftsartikel (refereegranskat)abstract
- MUC2, the major colonic mucin, forms large polymers by N-terminal trimerization and C-terminal dimerization. Although the assembly process for MUC2 is established, it is not known how MUC2 is packed in the regulated secretory granulae of the goblet cell. When the N-terminal VWD1-D2-D'D3 domains (MUC2-N) were expressed in a goblet-like cell line, the protein was stored together with full-length MUC2. By mimicking the pH and calcium conditions of the secretory pathway we analyzed purified MUC2-N by gel filtration, density gradient centrifugation, and transmission electron microscopy. At pH 7.4 the MUC2-N trimer eluted as a single peak by gel filtration. At pH 6.2 with Ca(2+) it formed large aggregates that did not enter the gel filtration column but were made visible after density gradient centrifugation. Electron microscopy studies revealed that the aggregates were composed of rings also observed in secretory granulae of colon tissue sections. The MUC2-N aggregates were dissolved by removing Ca(2+) and raising pH. After release from goblet cells, the unfolded full-length MUC2 formed stratified layers. These findings suggest a model for mucin packing in the granulae and the mechanism for mucin release, unfolding, and expansion.
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| 14. |
- Andersson, Marlene, et al.
(författare)
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Biomimetic spinning of artificial spider silk from a chimeric minispidroin
- 2017
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Ingår i: Nature Chemical Biology. - : Nature Publishing Group. - 1552-4450 .- 1552-4469. ; 13:3, s. 262-
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Tidskriftsartikel (refereegranskat)abstract
- Herein we present a chimeric recombinant spider silk protein (spidroin) whose aqueous solubility equals that of native spider silk dope and a spinning device that is based solely on aqueous buffers, shear forces and lowered pH. The process recapitulates the complex molecular mechanisms that dictate native spider silk spinning and is highly efficient; spidroin from one liter of bacterial shake-flask culture is enough to spin a kilometer of the hitherto toughest as-spun artificial spider silk fiber.
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| 15. |
- Andersson, Marlene, et al.
(författare)
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Biomimetic spinning of artificial spider silk from a chimeric minispidroin
- 2017
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Ingår i: Nature Chemical Biology. - : Springer Science and Business Media LLC. - 1552-4450 .- 1552-4469. ; 254
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Tidskriftsartikel (refereegranskat)abstract
- Herein we present a chimeric recombinant spider silk protein (spidroin) whose aqueous solubility equals that of native spider silk dope and a spinning device that is based solely on aqueous buffers, shear forces and lowered pH. The process recapitulates the complex molecular mechanisms that dictate native spider silk spinning and is highly efficient; spidroin from one liter of bacterial shake-flask culture is enough to spin a kilometer of the hitherto toughest as-spun artificial spider silk fiber.
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| 16. |
- B. Kumar, Ramakrishnan, et al.
(författare)
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Method to Visualize and Analyze Membrane Interacting Proteins by Transmission Electron Microscopy
- 2017
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Ingår i: Journal of Visualized Experiments. - : Journal of Visualized Experiments. - 1940-087X. ; :121
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Tidskriftsartikel (refereegranskat)abstract
- Monotopic proteins exert their function when attached to a membrane surface, and such interactions depend on the specific lipid composition and on the availability of enough area to perform the function. Nanodiscs are used to provide a membrane surface of controlled size and lipid content. In the absence of bound extrinsic proteins, sodium phosphotungstate-stained nanodiscs appear as stacks of coins when viewed from the side by transmission electron microscopy (TEM). This protocol is therefore designed to intentionally promote stacking; consequently, the prevention of stacking can be interpreted as the binding of the membrane-binding protein to the nanodisc. In a further step, the TEM images of the protein-nanodisc complexes can be processed with standard single-particle methods to yield low-resolution structures as a basis for higher resolution cryoEM work. Furthermore, the nanodiscs provide samples suitable for either TEM or non-denaturing gel electrophoresis. To illustrate the method, Ca2+-induced binding of 5-lipoxygenase on nanodiscs is presented.
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| 17. |
- Balakrishnan Kumar, Ramakrishnan, et al.
(författare)
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Structural and Functional Analysis of Calcium Ion Mediated Binding of 5-Lipoxygenase to Nanodiscs
- 2016
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Ingår i: PLOS ONE. - : Public Library of Science. - 1932-6203. ; 11:3
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Tidskriftsartikel (refereegranskat)abstract
- An important step in the production of inflammatory mediators of the leukotriene family is the Ca2+ mediated recruitment of 5 Lipoxygenase (5LO) to nuclear membranes. To study this reaction in vitro, the natural membrane mimicking environment of nanodiscs was used. Nanodiscs with 10.5 nm inner diameter were made with the lipid POPC and membrane scaffolding protein MSP1E3D1. Monomeric and dimeric 5LO were investigated. Monomeric 5LO mixed with Ca2+ and nanodiscs are shown to form stable complexes that 1) produce the expected leukotriene products from arachidonic acid and 2) can be, for the first time, visualised by native gel electrophoresis and negative stain transmission electron micros-copy and 3) show a highest ratio of two 5LO per nanodisc. We interpret this as one 5LO on each side of the disc. The dimer of 5LO is visualised by negative stain transmission electron microscopy and is shown to not bind to nanodiscs. This study shows the advantages of nanodiscs to obtain basic structural information as well as functional information of a complex between a monotopic membrane protein and the membrane.
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| 18. |
- Braniste, Viorica, et al.
(författare)
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The gut microbiota influences blood-brain barrier permeability in mice
- 2014
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Ingår i: Science Translational Medicine. - : American Association for the Advancement of Science. - 1946-6234 .- 1946-6242. ; 6:263, s. 263ra158-
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Tidskriftsartikel (refereegranskat)abstract
- Pivotal to brain development and function is an intact blood-brain barrier (BBB), which acts as a gatekeeper to control the passage and exchange of molecules and nutrients between the circulatory system and the brain parenchyma. The BBB also ensures homeostasis of the central nervous system (CNS). We report that germ-free mice, beginning with intrauterine life, displayed increased BBB permeability compared to pathogen-free mice with a normal gut flora. The increased BBB permeability was maintained in germ-free mice after birth and during adulthood and was associated with reduced expression of the tight junction proteins occludin and claudin-5, which are known to regulate barrier function in endothelial tissues. Exposure of germ-free adult mice to a pathogen-free gut microbiota decreased BBB permeability and up-regulated the expression of tight junction proteins. Our results suggest that gut microbiota-BBB communication is initiated during gestation and propagated throughout life.
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| 19. |
- Brismar, Torkel B., et al.
(författare)
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Magnetite Nanoparticles Can Be Coupled to Microbubbles to Support Multimodal Imaging
- 2012
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 13:5, s. 1390-1399
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Tidskriftsartikel (refereegranskat)abstract
- Microbubbles (MBs) are commonly used as injectable ultrasound contrast agent (UCA) in modern ultrasonography. Polymer-shelled UCAs present additional potentialities with respect to marketed lipid-shelled UCAs. They are more robust; that is, they have longer shelf and circulation life, and surface modifications are quite easily accomplished to obtain enhanced targeting and local drug delivery. The next generation of UCAs will be required to support not only ultrasound-based imaging methods but also other complementary diagnostic approaches such as magnetic resonance imaging or computer tomography. This work addresses the features of MBs that could function as contrast agents for both ultrasound and magnetic resonance imaging. The results indicate that the introduction of iron oxide nanoparticles (SPIONs) in the poly(vinyl alcohol) shell or on the external surface of the MBs does not greatly decrease the echogenicity of the host MBs compared with the unmodified one. The presence of SPIONs provides enough magnetic susceptibility to the MBs to accomplish good detectability both in vitro and in vivo. The distribution of SPIONs on the shell and their aggregation state seem to be key factors for the optimization of the transverse relaxation rate.
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| 20. |
- Busenlehner, Laura S., et al.
(författare)
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Location of substrate binding sites within the integral membrane protein microsomal glutathione transferase-1
- 2007
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Ingår i: Biochemistry. - : American Chemical Society (ACS). - 0006-2960 .- 1520-4995. ; 46:10, s. 2812-2822
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Tidskriftsartikel (refereegranskat)abstract
- Microsomal glutathione transferase-1 (MGST1) is a trimeric, membrane-bound enzyme with both glutathione (GSH) transferase and hydroperoxidase activities. As a member of the MAPEG superfamily, MGST1 aids in the detoxication of numerous xenobiotic substrates and in cellular protection from oxidative stress through the GSH-dependent reduction of phospholipid hydroperoxides. However, little is known about the location of the different substrate binding sites, including whether the transferase and peroxidase activities overlap structurally. Although molecular density attributed to GSH has been observed in the 3.2 A resolution electron crystallographic structure of MGST1, the electrophilic and phospholipid hydroperoxide substrate binding sites remain elusive. Amide H-D exchange kinetics and H-D ligand footprinting experiments indicate that GSH and hydrophobic substrates bind within similar, but distinct, regions of MGST1. Site-directed mutagenesis, guided by the H-D exchange results, demonstrates that specific residues within the GSH footprint effect transferase activity toward 1-chloro-2,4-dinitrobenzene. In addition, cytosolic residues surrounding the chemical stress sensor C49 but not modeled in the crystal structure appear to play an important role in the formation of the binding site for hydrophobic substrates. Although the fatty acid/phospholipid binding site structurally overlaps that for GSH, it does not appear to be localized to the same region as other hydrophobic substrates. Finally, H-D exchange mass spectrometry reveals a specific conformational transition that may mediate substrate binding and/or product release. Such structural changes in MGST1 are essential for activation of the enzyme and are important for its biological function.
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| 21. |
- Busenlehner, L.S., et al.
(författare)
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Stress sensor triggers conformational response of the integral membrane protein microsomal glutathione transferase 1
- 2004
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Ingår i: Biochemistry. - : American Chemical Society (ACS). - 0006-2960 .- 1520-4995. ; 43:35, s. 11145-11152
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Tidskriftsartikel (refereegranskat)abstract
- Microsomal glutathione (GSH) transferase 1 (MGST1) is a trimeric, integral membrane protein involved in cellular response to chemical or oxidative stress. The cytosolic domain of MGST1 harbors the GSH binding site and a cysteine residue (C49) that acts as a sensor of oxidative and chemical stress. Spatially resolved changes in the kinetics of backbone amide H/D exchange reveal that the binding of a single molecule of GSH/trimer induces a cooperative conformational transition involving movements of the transmembrane helices and a reordering of the cytosolic domain. Alkylation of the stress sensor preorganizes the helices and facilitates the cooperative transition resulting in catalytic activation.
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| 22. |
- Chen, G., et al.
(författare)
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Abilities of the BRICHOS domain to prevent neurotoxicity and fibril formation are dependent on a highly conserved Asp residue
- 2022
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Ingår i: RSC Chemical Biology. - : Royal Society of Chemistry (RSC). - 2633-0679. ; 3:11, s. 1342-1358
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Tidskriftsartikel (refereegranskat)abstract
- Proteins can self-assemble into amyloid fibrils or amorphous aggregates and thereby cause disease. Molecular chaperones can prevent both these types of protein aggregation, but to what extent the respective mechanisms are overlapping is not fully understood. The BRICHOS domain constitutes a disease-associated chaperone family, with activities against amyloid neurotoxicity, fibril formation, and amorphous protein aggregation. Here, we show that the activities of BRICHOS against amyloid-induced neurotoxicity and fibril formation, respectively, are oppositely dependent on a conserved aspartate residue, while the ability to suppress amorphous protein aggregation is unchanged by Asp to Asn mutations. The Asp is evolutionarily highly conserved in >3000 analysed BRICHOS domains but is replaced by Asn in some BRICHOS families. The conserved Asp in its ionized state promotes structural flexibility and has a pKa value between pH 6.0 and 7.0, suggesting that chaperone effects can be differently affected by physiological pH variations.
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| 23. |
- Chen, G., et al.
(författare)
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Augmentation of Bri2 molecular chaperone activity against amyloid-β reduces neurotoxicity in mouse hippocampus in vitro
- 2020
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Ingår i: Communications Biology. - : Nature Research. - 2399-3642. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Molecular chaperones play important roles in preventing protein misfolding and its potentially harmful consequences. Deterioration of molecular chaperone systems upon ageing are thought to underlie age-related neurodegenerative diseases, and augmenting their activities could have therapeutic potential. The dementia relevant domain BRICHOS from the Bri2 protein shows qualitatively different chaperone activities depending on quaternary structure, and assembly of monomers into high-molecular weight oligomers reduces the ability to prevent neurotoxicity induced by the Alzheimer-associated amyloid-β peptide 1-42 (Aβ42). Here we design a Bri2 BRICHOS mutant (R221E) that forms stable monomers and selectively blocks a main source of toxic species during Aβ42 aggregation. Wild type Bri2 BRICHOS oligomers are partly disassembled into monomers in the presence of the R221E mutant, which leads to potentiated ability to prevent Aβ42 toxicity to neuronal network activity. These results suggest that the activity of endogenous molecular chaperones may be modulated to enhance anti-Aβ42 neurotoxic effects.
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| 24. |
- Chen, Gefei, et al.
(författare)
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Bri2 BRICHOS client specificity and chaperone activity are governed by assembly state
- 2017
-
Ingår i: Nature Communications. - : Nature Publishing Group. - 2041-1723. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- . Protein misfolding and aggregation is increasingly being recognized as a cause of disease. In Alzheimer's disease the amyloid-beta peptide (A beta) misfolds into neurotoxic oligomers and assembles into amyloid fibrils. The Bri2 protein associated with Familial British and Danish dementias contains a BRICHOS domain, which reduces A beta fibrillization as well as neurotoxicity in vitro and in a Drosophila model, but also rescues proteins from irreversible nonfibrillar aggregation. How these different activities are mediated is not known. Here we show that Bri2 BRICHOS monomers potently prevent neuronal network toxicity of A beta, while dimers strongly suppress A beta fibril formation. The dimers assemble into high-molecular-weight oligomers with an apparent two-fold symmetry, which are efficient inhibitors of non-fibrillar protein aggregation. These results indicate that Bri2 BRICHOS affects qualitatively different aspects of protein misfolding and toxicity via different quaternary structures, suggesting a means to generate molecular chaperone diversity.
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| 25. |
- Chen, Gefei, et al.
(författare)
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Molecular basis for different substrate-binding sites and chaperone functions of the BRICHOS domain
- 2024
-
Ingår i: Protein Science. - : Wiley. - 0961-8368 .- 1469-896X. ; 33:7
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Tidskriftsartikel (refereegranskat)abstract
- Proteins can misfold into fibrillar or amorphous aggregates and molecular chaperones act as crucial guardians against these undesirable processes. The BRICHOS chaperone domain, found in several otherwise unrelated proproteins that contain amyloidogenic regions, effectively inhibits amyloid formation and toxicity but can in some cases also prevent non-fibrillar, amorphous protein aggregation. Here, we elucidate the molecular basis behind the multifaceted chaperone activities of the BRICHOS domain from the Bri2 proprotein. High-confidence AlphaFold2 and RoseTTAFold predictions suggest that the intramolecular amyloidogenic region (Bri23) is part of the hydrophobic core of the proprotein, where it occupies the proposed amyloid binding site, explaining the markedly reduced ability of the proprotein to prevent an exogenous amyloidogenic peptide from aggregating. However, the BRICHOS-Bri23 complex maintains its ability to form large polydisperse oligomers that prevent amorphous protein aggregation. A cryo-EM-derived model of the Bri2 BRICHOS oligomer is compatible with surface-exposed hydrophobic motifs that get exposed and come together during oligomerization, explaining its effects against amorphous aggregation. These findings provide a molecular basis for the BRICHOS chaperone domain function, where distinct surfaces are employed against different forms of protein aggregation.
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