Zeitschriftenartikel: „Protein movements“

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Cox, Sarah, Elzbieta Radzio-Andzelm und Susan Serota Taylor. „Domain movements in protein kinases“. Current Opinion in Structural Biology 4, Nr. 6 (Januar 1994): 893–901. http://dx.doi.org/10.1016/0959-440x(94)90272-0.

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Kuffel, Anna, und Jan Zielkiewicz. „Water-mediated long-range interactions between the internal vibrations of remote proteins“. Physical Chemistry Chemical Physics 17, Nr. 10 (2015): 6728–33. http://dx.doi.org/10.1039/c5cp00090d.

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Messant, Marine, Anja Krieger-Liszkay und Ginga Shimakawa. „Dynamic Changes in Protein-Membrane Association for Regulating Photosynthetic Electron Transport“. Cells 10, Nr. 5 (16.05.2021): 1216. http://dx.doi.org/10.3390/cells10051216.

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Photosynthesis has to work efficiently in contrasting environments such as in shade and full sun. Rapid changes in light intensity and over-reduction of the photosynthetic electron transport chain cause production of reactive oxygen species, which can potentially damage the photosynthetic apparatus. Thus, to avoid such damage, photosynthetic electron transport is regulated on many levels, including light absorption in antenna, electron transfer reactions in the reaction centers, and consumption of ATP and NADPH in different metabolic pathways. Many regulatory mechanisms involve the movement of protein-pigment complexes within the thylakoid membrane. Furthermore, a certain number of chloroplast proteins exist in different oligomerization states, which temporally associate to the thylakoid membrane and modulate their activity. This review starts by giving a short overview of the lipid composition of the chloroplast membranes, followed by describing supercomplex formation in cyclic electron flow. Protein movements involved in the various mechanisms of non-photochemical quenching, including thermal dissipation, state transitions and the photosystem II damage–repair cycle are detailed. We highlight the importance of changes in the oligomerization state of VIPP and of the plastid terminal oxidase PTOX and discuss the factors that may be responsible for these changes. Photosynthesis-related protein movements and organization states of certain proteins all play a role in acclimation of the photosynthetic organism to the environment.

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Platani, Melpomeni, Ilya Goldberg, Jason R. Swedlow und Angus I. Lamond. „In Vivo Analysis of Cajal Body Movement, Separation, and Joining in Live Human Cells“. Journal of Cell Biology 151, Nr. 7 (25.12.2000): 1561–74. http://dx.doi.org/10.1083/jcb.151.7.1561.

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Cajal bodies (also known as coiled bodies) are subnuclear organelles that contain specific nuclear antigens, including splicing small nuclear ribonucleoproteins (snRNPs) and a subset of nucleolar proteins. Cajal bodies are localized in the nucleoplasm and are often found at the nucleolar periphery. We have constructed a stable HeLa cell line, HeLaGFP-coilin, that expresses the Cajal body marker protein, p80 coilin, fused to the green fluorescent protein (GFP-coilin). The localization pattern and biochemical properties of the GFP-coilin fusion protein are identical to the endogenous p80 coilin. Time-lapse recordings on 63 nuclei of HeLaGFP-coilin cells showed that all Cajal bodies move within the nucleoplasm. Movements included translocations through the nucleoplasm, joining of bodies to form larger structures, and separation of smaller bodies from larger Cajal bodies. Also, we observed Cajal bodies moving to and from nucleoli. The data suggest that there may be at least two classes of Cajal bodies that differ in their size, antigen composition, and dynamic behavior. The smaller size class shows more frequent and faster rates of movement, up to 0.9 μm/min. The GFP-coilin protein is dynamically associated with Cajal bodies as shown by changes in their fluorescence intensity over time. This study reveals an unexpectedly high level of movement and interactions of nuclear bodies in human cells and suggests that these movements may be driven, at least in part, by regulated mechanisms.

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Chudakov, Dmitriy M., Sergey Lukyanov und Konstantin A. Lukyanov. „Tracking intracellular protein movements using photoswitchable fluorescent proteins PS-CFP2 and Dendra2“. Nature Protocols 2, Nr. 8 (August 2007): 2024–32. http://dx.doi.org/10.1038/nprot.2007.291.

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Kuznetsov, A. V., I. Yu Grishin und D. N. Vtyurina. „Spatial Models of Piezoproteins and Networks of Protein-Protein Interactions in Trichoplax Animals (Placozoa)“. Молекулярная биология 57, Nr. 5 (01.09.2023): 895–97. http://dx.doi.org/10.31857/s0026898423050075.

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The marine free-living organism Trichoplax (phylum Placozoa) resembles the unicellular amoeba in shape and type of movement. Trichoplax diverged from the main evolutionary tree in the Neoproterozoic Era and is one of the simplest models of a multicellular animal, as well as a strong example of the ensemble of interacting cells in an organism during its development and movement. Two orthologs of mouse Piezo1 protein (6B3R) were found in two Trichoplax haplotypes H1 and H2 as a result of a search for similar sequences in the NCBI databases. Spatial models of the corresponding proteins, XP_002112008.1 and RDD46920.1, were created based on the structural alignment using a 6KG7 (mouse Piezo2) template. The analysis of domain structures was performed, and a limited graph of protein‒protein interactions of the hypothetical mechanosensor XP_002112008.1 was constructed. The possibility of signal transduction from the mechanoreceptor to membrane complexes, cytoplasm and cell nucleus was shown. It is assumed that mechanosensory receptors of Trichoplax are involved in the perception of force stimuli between neighboring cells and the environment. Based on the obtained data, we propose to use the primitive Trichoplax organism as the simplest multicellular model for mechanical and morphogenetic movements.

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Roberts, G. C. K. „Folding and unfolding for binding: large-scale protein dynamics in protein–protein interactions“. Biochemical Society Transactions 34, Nr. 5 (01.10.2006): 971–74. http://dx.doi.org/10.1042/bst0340971.

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The role of dynamics in the function of proteins, from enzymes to signalling proteins, is widely recognized. In many cases, the dynamic process is a relatively localized one, involving motion of a limited number of key residues, while in others large-scale domain movements may be involved. These motions all take place within the context of a folded protein; however, there is increasing evidence for the existence of some proteins where a transition between folded and unfolded structures is required for function.

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Wako, Hiroshi, und Shigeru Endo. „ProMode-Oligomer: Database of Normal Mode Analysis in Dihedral Angle Space for a Full-Atom System of Oligomeric Proteins“. Open Bioinformatics Journal 6, Nr. 1 (21.02.2012): 9–19. http://dx.doi.org/10.2174/1875036201206010009.

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The database ProMode-Oligomer (http://promode.socs.waseda.ac.jp/promode_oligomer) was constructed by collecting normal-mode-analysis (NMA) results for oligomeric proteins including protein-protein complexes. As in the ProMode database developed earlier for monomers and individual subunits of oligomers (Bioinformatics vol. 20, pp. 2035–2043, 2004), NMA was performed for a full-atom system using dihedral angles as independent variables, and we released the results (fluctuations of atoms, fluctuations of dihedral angles, correlations between atomic fluctuations, etc.). The vibrating oligomer is visualized by animation in an interactive molecular viewer for each of the 20 lowest-frequency normal modes. In addition, displacement vectors of constituent atoms for each normal mode were decomposed into two characteristic motions in individual subunits, i.e., internal and external (deformation and rigid-body movements of the individual subunits, respectively), and then the mutual movements of the subunits and the movement of atoms around the interface regions were investigated. These results released in ProMode-Oligomer are useful for characterizing oligomeric proteins from a dynamic point of view. The analyses are illustrated with immunoglobulin light- and heavy-chain variable domains bound to lysozyme and to a 12-residue peptide.

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Suetsugu, Noriyuki, Atsushi Takemiya, Sam-Geun Kong, Takeshi Higa, Aino Komatsu, Ken-ichiro Shimazaki, Takayuki Kohchi und Masamitsu Wada. „RPT2/NCH1 subfamily of NPH3-like proteins is essential for the chloroplast accumulation response in land plants“. Proceedings of the National Academy of Sciences 113, Nr. 37 (30.08.2016): 10424–29. http://dx.doi.org/10.1073/pnas.1602151113.

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In green plants, the blue light receptor kinase phototropin mediates various photomovements and developmental responses, such as phototropism, chloroplast photorelocation movements (accumulation and avoidance), stomatal opening, and leaf flattening, which facilitate photosynthesis. In Arabidopsis, two phototropins (phot1 and phot2) redundantly mediate these responses. Two phototropin-interacting proteins, NONPHOTOTROPIC HYPOCOTYL 3 (NPH3) and ROOT PHOTOTROPISM 2 (RPT2), which belong to the NPH3/RPT2-like (NRL) family of BTB (broad complex, tramtrack, and bric à brac) domain proteins, mediate phototropism and leaf flattening. However, the roles of NRL proteins in chloroplast photorelocation movement remain to be determined. Here, we show that another phototropin-interacting NRL protein, NRL PROTEIN FOR CHLOROPLAST MOVEMENT 1 (NCH1), and RPT2 redundantly mediate the chloroplast accumulation response but not the avoidance response. NPH3, RPT2, and NCH1 are not involved in the chloroplast avoidance response or stomatal opening. In the liverwort Marchantia polymorpha, the NCH1 ortholog, MpNCH1, is essential for the chloroplast accumulation response but not the avoidance response, indicating that the regulation of the phototropin-mediated chloroplast accumulation response by RPT2/NCH1 is conserved in land plants. Thus, the NRL protein combination could determine the specificity of diverse phototropin-mediated responses.

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Hollenbeck, P. J., und D. Bray. „Rapidly transported organelles containing membrane and cytoskeletal components: their relation to axonal growth.“ Journal of Cell Biology 105, Nr. 6 (01.12.1987): 2827–35. http://dx.doi.org/10.1083/jcb.105.6.2827.

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We have examined the movements, composition, and cellular origin of phase-dense varicosities in cultures of chick sympathetic and sensory neurons. These organelles are variable in diameter (typically between 0.2 and 2 microns) and undergo saltatory movements both towards and away from the neuronal cell body. Their mean velocities vary inversely with the size of the organelle and are greater in the retrograde than the anterograde direction. Organelles stain with the lipophilic dye 1, 1'-dioctadecyl-3,3,3',3'-tetramethyl-indocarbocyanine and with antibodies to cytoskeletal components. In cultures double-stained with antibodies to alpha-tubulin and 70-kD neurofilament protein (NF-L), approximately 40% of the organelles stain for tubulin, 30% stain for NF-L, 10% stain for both tubulin and NF-L, and 40% show no staining with either antibody. The association of cytoskeletal proteins with the organelles shows that these proteins are able to move by a form of rapid axonal transport. Under most culture conditions the predominant direction of movement is towards the cell body, suggesting that the organelles are produced at or near the growth cone. Retrograde movements continue in culture medium lacking protein or high molecular mass components and increase under conditions in which the advance of the growth cone is arrested. There is a fourfold increase in the number of organelles moving retrogradely in neurites that encounter a substratum-associated barrier to elongation; retrograde movements increase similarly in cultures exposed to cytochalasin at levels known to block growth cone advance. No previously described organelle shows behavior coordinated with axonal growth in this way. We propose that the organelles contain membrane and cytoskeletal components that have been delivered to the growth cone, by slow or fast anterograde transport, in excess of the amounts required to synthesize more axon. In view of their rapid mobility and variable contents, we suggest that they be called "neuronal parcels."

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Lee, Hyun-Shik, Kathleen Mood, Gopala Battu, Yon Ju Ji, Arvinder Singh und Ira O. Daar. „Fibroblast Growth Factor Receptor-induced Phosphorylation of EphrinB1 Modulates Its Interaction with Dishevelled“. Molecular Biology of the Cell 20, Nr. 1 (Januar 2009): 124–33. http://dx.doi.org/10.1091/mbc.e08-06-0662.

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The Eph family of receptor tyrosine kinases and their membrane-bound ligands, the ephrins, have been implicated in regulating cell adhesion and migration during development by mediating cell-to-cell signaling events. The transmembrane ephrinB1 protein is a bidirectional signaling molecule that signals through its cytoplasmic domain to promote cellular movements into the eye field, whereas activation of the fibroblast growth factor receptor (FGFR) represses these movements and retinal fate. In Xenopus embryos, ephrinB1 plays a role in retinal progenitor cell movement into the eye field through an interaction with the scaffold protein Dishevelled (Dsh). However, the mechanism by which the FGFR may regulate this cell movement is unknown. Here, we present evidence that FGFR-induced repression of retinal fate is dependent upon phosphorylation within the intracellular domain of ephrinB1. We demonstrate that phosphorylation of tyrosines 324 and 325 disrupts the ephrinB1/Dsh interaction, thus modulating retinal progenitor movement that is dependent on the planar cell polarity pathway. These results provide mechanistic insight into how fibroblast growth factor signaling modulates ephrinB1 control of retinal progenitor movement within the eye field.

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Norimatsu, Yoshiyuki, Junko Tsueda, Ayami Hirata, Shiho Iwasawa und Chikashi Toyoshima. „Visualization of lipid bilayer in the crystals by solvent contrast modulation“. Acta Crystallographica Section A Foundations and Advances 70, a1 (05.08.2014): C1498. http://dx.doi.org/10.1107/s2053273314085015.

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A new method of X-ray solvent contrast modulation was developed to visualize lipid bilayers in crystals of membrane proteins at a high enough resolution to resolve individual phospholipids molecules (~3.5 Å ). Visualization of lipid bilayer has been escaping from conventional crystallographic methods due to its extreme flexibility, and our knowledge on the behavior of lipid bilayer is still very much limited. Here we applied the new method of X-ray solvent contrast modulation to crystals of Ca2+-ATPase in 4 different physiological states. As phospholipids have to be added to make crystals of Ca2+-ATPase, it is expected that lipid bilayers are present in the crystals. Moreover, transmembrane helices of Ca2+-ATPase rearrange drastically during the reaction cycle and some of them show substantial movements perpendicular to the bilayer plane. Thus these crystals provide a rare opportunity to directly visualize phospholipids interacting with a membrane protein in different conformations. Complete diffraction data covering from 200 to 3.2 Å resolution were collected at BL41XU, Spring-8, using an R-Axis V imaging plate detector for crystals soaked in solvent of different electron density. A new concept "solvent exchange probability", which should be 1 in the bulk solvent, 0 inside the protein and an intermediate at interface, was introduced and used as a restraint for real space phase improvement. The electron density maps thus obtained clearly show that: (i) Phospholipid molecules surrounding the protein are fixed apparently by Arg/Lys-phosphate salt bridges or Trp-carbonyl hydrogen bonds and follow the movements of transmembrane helices. Movements of as large as 12 Å are allowed. (ii) If the movement of a transmembrane helix exceeds this limit, associated phospholipids change the partners for fixation or change the orientation of the entire protein molecule.

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Zhuravlev, Pavel I., Michael Hinczewski, Shaon Chakrabarti, Susan Marqusee und D. Thirumalai. „Force-dependent switch in protein unfolding pathways and transition-state movements“. Proceedings of the National Academy of Sciences 113, Nr. 6 (27.01.2016): E715—E724. http://dx.doi.org/10.1073/pnas.1515730113.

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Although it is known that single-domain proteins fold and unfold by parallel pathways, demonstration of this expectation has been difficult to establish in experiments. Unfolding rate, ku(f), as a function of force f, obtained in single-molecule pulling experiments on src SH3 domain, exhibits upward curvature on a log⁡ku(f) plot. Similar observations were reported for other proteins for the unfolding rate ku([C]). These findings imply unfolding in these single-domain proteins involves a switch in the pathway as f or [C] is increased from a low to a high value. We provide a unified theory demonstrating that if log⁡ku as a function of a perturbation (f or [C]) exhibits upward curvature then the underlying energy landscape must be strongly multidimensional. Using molecular simulations we provide a structural basis for the switch in the pathways and dramatic shifts in the transition-state ensemble (TSE) in src SH3 domain as f is increased. We show that a single-point mutation shifts the upward curvature in log⁡ku(f) to a lower force, thus establishing the malleability of the underlying folding landscape. Our theory, applicable to any perturbation that affects the free energy of the protein linearly, readily explains movement in the TSE in a β-sandwich (I27) protein and single-chain monellin as the denaturant concentration is varied. We predict that in the force range accessible in laser optical tweezer experiments there should be a switch in the unfolding pathways in I27 or its mutants.

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Malycheva, Darina, und Maria Alvarado-Kristensson. „Centrosome Movements Are TUBG1-Dependent“. International Journal of Molecular Sciences 24, Nr. 17 (24.08.2023): 13154. http://dx.doi.org/10.3390/ijms241713154.

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The centrosome of mammalian cells is in constant movement and its motion plays a part in cell differentiation and cell division. The purpose of this study was to establish the involvement of the TUBG meshwork in centrosomal motility. In live cells, we used a monomeric red-fluorescence-protein-tagged centrin 2 gene and a green-fluorescence-protein-tagged TUBG1 gene for labeling the centrosome and the TUBG1 meshwork, respectively. We found that centrosome movements occurred in cellular sites rich in GTPase TUBG1 and single-guide RNA mediated a reduction in the expression of TUBG1, altering the motility pattern of centrosomes. We propose that the TUBG1 meshwork enables the centrosomes to move by providing them with an interacting platform that mediates positional changes. These findings uncover a novel regulatory mechanism that controls the behavior of centrosomes.

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Geada, María M., Inmaculada Galindo, María M. Lorenzo, Beatriz Perdiguero und Rafael Blasco. „Movements of vaccinia virus intracellular enveloped virions with GFP tagged to the F13L envelope protein“. Journal of General Virology 82, Nr. 11 (01.11.2001): 2747–60. http://dx.doi.org/10.1099/0022-1317-82-11-2747.

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Vaccinia virus produces several forms of infectious virions. Intracellular mature virions (IMV) assemble in areas close to the cell nucleus. Some IMV acquire an envelope from intracellular membranes derived from the trans-Golgi network, producing enveloped forms found in the cytosol (intracellular enveloped virus; IEV), on the cell surface (cell-associated enveloped virus) or free in the medium (extracellular enveloped virus; EEV). Blockage of IMV envelopment inhibits transport of virions to the cell surface, indicating that enveloped virus forms are required for virion movement from the Golgi area. To date, the induction of actin tails that propel IEV is the only well-characterized mechanism for enveloped virus transport. However, enveloped virus transport and release occur under conditions where actin tails are not formed. In order to study these events, recombinant vaccinia viruses were constructed with GFP fused to the most abundant protein in the EEV envelope, P37 (F13L). The P37–GFP fusion, like normal P37, accumulated in the Golgi area and was incorporated efficiently into enveloped virions. These recombinants allowed the monitoring of enveloped virus movements in vivo. In addition to a variety of relatively slow movements (<0·4 μm/s), faster, saltatory movements both towards and away from the Golgi area were observed. These movements were different from those dependent on actin tails and were inhibited by the microtubule-disrupting drug nocodazole, but not by the myosin inhibitor 2,3-butanedione monoxime. Video microscopy (5 frames per s) revealed that saltatory movements had speeds of up to, and occasionally more than, 3 μm/s. These results suggest that a second, microtubule-dependent mechanism exists for intracellular transport of enveloped vaccinia virions.

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Chabrillat, Marion L., Claire Wilhelm, Christina Wasmeier, Elena V. Sviderskaya, Daniel Louvard und Evelyne Coudrier. „Rab8 Regulates the Actin-based Movement of Melanosomes“. Molecular Biology of the Cell 16, Nr. 4 (April 2005): 1640–50. http://dx.doi.org/10.1091/mbc.e04-09-0770.

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Rab GTPases have been implicated in the regulation of specific microtubule- and actin-based motor proteins. We devised an in vitro motility assay reconstituting the movement of melanosomes on actin bundles in the presence of ATP to investigate the role of Rab proteins in the actin-dependent movement of melanosomes. Using this assay, we confirmed that Rab27 is required for the actin-dependent movement of melanosomes, and we showed that a second Rab protein, Rab8, also regulates this movement. Rab8 was partially associated with mature melanosomes. Expression of Rab8Q67L perturbed the cellular distribution and increased the frequency of microtubule-independent movement of melanosomes in vivo. Furthermore, anti-Rab8 antibodies decreased the number of melanosomes moving in vitro on actin bundles, whereas melanosomes isolated from cells expressing Rab8Q67L exhibited 70% more movements than wild-type melanosomes. Together, our observations suggest that Rab8 is involved in regulating the actin-dependent movement of melanosomes.

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Yuan, Zixuan, und Scott B. Hansen. „Cholesterol Regulation of Membrane Proteins Revealed by Two-Color Super-Resolution Imaging“. Membranes 13, Nr. 2 (20.02.2023): 250. http://dx.doi.org/10.3390/membranes13020250.

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Cholesterol and phosphatidyl inositol 4,5-bisphosphate (PIP2) are hydrophobic molecules that regulate protein function in the plasma membrane of all cells. In this review, we discuss how changes in cholesterol concentration cause nanoscopic (<200 nm) movements of membrane proteins to regulate their function. Cholesterol is known to cluster many membrane proteins (often palmitoylated proteins) with long-chain saturated lipids. Although PIP2 is better known for gating ion channels, in this review, we will discuss a second independent function as a regulator of nanoscopic protein movement that opposes cholesterol clustering. The understanding of the movement of proteins between nanoscopic lipid domains emerged largely through the recent advent of super-resolution imaging and the establishment of two-color techniques to label lipids separate from proteins. We discuss the labeling techniques for imaging, their strengths and weakness, and how they are used to reveal novel mechanisms for an ion channel, transporter, and enzyme function. Among the mechanisms, we describe substrate and ligand presentation and their ability to activate enzymes, gate channels, and transporters rapidly and potently. Finally, we define cholesterol-regulated proteins (CRP) and discuss the role of PIP2 in opposing the regulation of cholesterol, as seen through super-resolution imaging.

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Kim, Su Kyoung, Asako Shindo, Tae Joo Park, Edwin C. Oh, Srimoyee Ghosh, Ryan S. Gray, Richard A. Lewis et al. „Planar Cell Polarity Acts Through Septins to Control Collective Cell Movement and Ciliogenesis“. Science 329, Nr. 5997 (29.07.2010): 1337–40. http://dx.doi.org/10.1126/science.1191184.

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The planar cell polarity (PCP) signaling pathway governs collective cell movements during vertebrate embryogenesis, and certain PCP proteins are also implicated in the assembly of cilia. The septins are cytoskeletal proteins controlling behaviors such as cell division and migration. Here, we identified control of septin localization by the PCP protein Fritz as a crucial control point for both collective cell movement and ciliogenesis in Xenopus embryos. We also linked mutations in human Fritz to Bardet-Biedl and Meckel-Gruber syndromes, a notable link given that other genes mutated in these syndromes also influence collective cell movement and ciliogenesis. These findings shed light on the mechanisms by which fundamental cellular machinery, such as the cytoskeleton, is regulated during embryonic development and human disease.

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Sanger, J. M., B. Mittal, F. S. Southwick und J. W. Sanger. „Intracellular motility and actin polymerization induced by Listeria monocytogenes in infected cells“. Proceedings, annual meeting, Electron Microscopy Society of America 49 (August 1991): 166–67. http://dx.doi.org/10.1017/s0424820100085137.

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The bacterium, Listeria monocytogenes can be phagocytosed by macrophages and epithelial cells. Within an hour, the bacteria can assemble host cell actin into bundles or tails and move inside the living cells at rates up to 1.4μm/sec. In seeking to determine the mechanisms responsible for the intracellular movements of this bacterium, our working hypothesis is that actin polymerization is not only necessary for the movement but the polymerization reaction itself provides the force to move the bacteria in the host cytoplasm.PtK2 cells, an epithelial cell line, were infected with Listeria and were then microinjected with fluorescently labeled cytoskeletal proteins (actin, alpha-actinin, filamin, tropomyosin, skeletal muscle light chains) and a control fluorescent protein (bovine serum albumin, BSA). Some infected cells were sequentially injected first with fluorescently labeled cytoskeletal proteins and then with proteins that bind monomelic actin (Vitamin-D binding protein; DNAase I; profilin).

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Hamm-Alvarez, S. F., X. Wei, N. Berndt und M. Runnegar. „Protein phosphatases independently regulate vesicle movement and microtubule subpopulations in hepatocytes“. American Journal of Physiology-Cell Physiology 271, Nr. 3 (01.09.1996): C929—C943. http://dx.doi.org/10.1152/ajpcell.1996.271.3.c929.

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To investigate the regulation of microtubule (MT)-based vesicle transport and the interphase MT array in hepatocytes, we have used okadaic acid (OKA) and microcystin (MCYST), two toxins that inhibit serine-threonine protein phosphatases (PP) 1 and 2A, to alter cellular phosphorylation. Video-enhanced differential interference contrast microscopy analysis revealed that both toxins inhibited the frequency, velocity, and run length of MT-dependent vesicle movements dose dependently between 50 and 500 nM. At our maximum dose of 500 nM, both toxins significantly decreased PP2A activity (OKA to 45 +/- 12% and MCYST to 57 +/- 2%), whereas PP1 was inhibited only by MCYST. Because no additional effects on vesicle movements were caused by MCYST over the changes caused by OKA, these data implicate PP2A in the regulation of MT-dependent vesicle movement. To understand whether the changes in parameters of vesicle movements were due to changes in the MT array, the effects of these toxins on MT distribution were examined by immunofluorescence microscopy. Although lower doses of OKA produced no effects, treatment with 500 nM OKA altered MT organization and also caused fragmentation and loss of acetylated (stable) MTs. In contrast, MCYST concentrations up to 500 nM elicited no changes in MT organization in general or in the acetylated (stable) array. From these findings we conclude that inhibition of MT-dependent vesicle movement by the PP inhibitors, MCYST and OKA, in hepatocytes cannot result from changes or disruption in the MT array. Because OKA (an inhibitor of PP2A only in our system) at high doses caused loss of stable MTs, whereas MCYST (an inhibitor of both PP1 and PP2A) did not, we conclude that the control of the preservation of the stable MT array in hepatocytes is complex. Stable MTs require active PP2A for maintenance, but the disruption of the array through inhibition of PP2A can be prevented if PP1 is also inhibited, suggesting that the relative degree of phosphorylation of multiple cellular components is the determinant of MT stability.

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Klemm, Anna H., Agneza Bosilj, Matko Gluncˇic´, Nenad Pavin und Iva M. Tolic´. „Metaphase kinetochore movements are regulated by kinesin-8 motors and microtubule dynamic instability“. Molecular Biology of the Cell 29, Nr. 11 (Juni 2018): 1332–45. http://dx.doi.org/10.1091/mbc.e17-11-0667.

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During metaphase, sister chromatids are connected to microtubules extending from the opposite spindle poles via kinetochores to protein complexes on the chromosome. Kinetochores congress to the equatorial plane of the spindle and oscillate around it, with kinesin-8 motors restricting these movements. Yet, the physical mechanism underlying kinetochore movements is unclear. We show that kinetochore movements in the fission yeast Schizosaccharomyces pombe are regulated by kinesin-8-promoted microtubule catastrophe, force-induced rescue, and microtubule dynamic instability. A candidate screen showed that among the selected motors only kinesin-8 motors Klp5/Klp6 are required for kinetochore centering. Kinesin-8 accumulates at the end of microtubules, where it promotes catastrophe. Laser ablation of the spindle resulted in kinetochore movement toward the intact spindle pole in wild-type and klp5Δ cells, suggesting that kinetochore movement is driven by pulling forces. Our theoretical model with Langevin description of microtubule dynamic instability shows that kinesin-8 motors are required for kinetochore centering, whereas sensitivity of rescue to force is necessary for the generation of oscillations. We found that irregular kinetochore movements occur for a broader range of parameters than regular oscillations. Thus, our work provides an explanation for how regulation of microtubule dynamic instability contributes to kinetochore congression and the accompanying movements around the spindle center.

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Petrova, T., S. Ginell, A. Mitschler, Y. Kim, V. Y. Lunin, G. Joachimiak, A. Cousido-Siah et al. „X-ray-induced cooperative atomic movements in protein crystals“. Acta Crystallographica Section A Foundations of Crystallography 67, a1 (22.08.2011): C655. http://dx.doi.org/10.1107/s0108767311083449.

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Pickover, Clifford A. „DNA and protein tetragrams: Biological sequences as tetrahedral movements“. Journal of Molecular Graphics 10, Nr. 1 (März 1992): 2–6. http://dx.doi.org/10.1016/0263-7855(92)80001-t.

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Boggon, Titus J., Naomi E. Chayen, Edward H. Snell, Jun Dong, Peter Lautenschlager, Lothar Potthast, D. Peter Siddons et al. „Protein crystal movements and fluid flows during microgravity growth“. Philosophical Transactions of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences 356, Nr. 1739 (15.04.1998): 1045–61. http://dx.doi.org/10.1098/rsta.1998.0208.

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Petrova, Tatiana, Vladimir Y. Lunin, Stephan Ginell, Isabelle Hazemann, Krzysztof Lazarski, André Mitschler, Alberto Podjarny und Andrzej Joachimiak. „X-Ray-Radiation-Induced Cooperative Atomic Movements in Protein“. Journal of Molecular Biology 387, Nr. 5 (April 2009): 1092–105. http://dx.doi.org/10.1016/j.jmb.2009.02.030.

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Sahakian, Harutyun, Karen Nazarian, Arcady Mushegian und Irina Sorokina. „Energy-dependent protein folding: modeling how a protein folding machine may work“. F1000Research 10 (05.01.2021): 3. http://dx.doi.org/10.12688/f1000research.28175.1.

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Background: Proteins fold robustly and reproducibly in vivo, but many cannot fold in vitro in isolation from cellular components. Despite the remarkable progress that has been achieved by the artificial intelligence approaches in predicting the protein native conformations, the pathways that lead to such conformations, either in vitro or in vivo, remain largely unknown. The slow progress in recapitulating protein folding pathways in silico may be an indication of the fundamental deficiencies in our understanding of folding as it occurs in nature. Here we consider the possibility that protein folding in living cells may not be driven solely by the decrease in Gibbs free energy and propose that protein folding in vivo should be modeled as an active energy-dependent process. The mechanism of action of such a protein folding machine might include direct manipulation of the peptide backbone. Methods: To show the feasibility of a protein folding machine, we conducted molecular dynamics simulations that were augmented by the application of mechanical force to rotate the C-terminal amino acid while simultaneously limiting the N-terminal amino acid movements. Results: Remarkably, the addition of this simple manipulation of peptide backbones to the standard molecular dynamics simulation indeed facilitated the formation of native structures in five diverse alpha-helical peptides. Steric clashes that arise in the peptides due to the forced directional rotation resulted in the behavior of the peptide backbone no longer resembling a freely jointed chain. Conclusions: These simulations show the feasibility of a protein folding machine operating under the conditions when the movements of the polypeptide backbone are restricted by applying external forces and constraints. Further investigation is needed to see whether such an effect may play a role during co-translational protein folding in vivo and how it can be utilized to facilitate folding of proteins in artificial environments.

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Cordonnier, Marie-Neige, Daniel Dauzonne, Daniel Louvard und Evelyne Coudrier. „Actin Filaments and Myosin I Alpha Cooperate with Microtubules for the Movement of Lysosomes“. Molecular Biology of the Cell 12, Nr. 12 (Dezember 2001): 4013–29. http://dx.doi.org/10.1091/mbc.12.12.4013.

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An earlier report suggested that actin and myosin I alpha (MMIα), a myosin associated with endosomes and lysosomes, were involved in the delivery of internalized molecules to lysosomes. To determine whether actin and MMIα were involved in the movement of lysosomes, we analyzed by time-lapse video microscopy the dynamic of lysosomes in living mouse hepatoma cells (BWTG3 cells), producing green fluorescent protein actin or a nonfunctional domain of MMIα. In GFP-actin cells, lysosomes displayed a combination of rapid long-range directional movements dependent on microtubules, short random movements, and pauses, sometimes on actin filaments. We showed that the inhibition of the dynamics of actin filaments by cytochalasin D increased pauses of lysosomes on actin structures, while depolymerization of actin filaments using latrunculin A increased the mobility of lysosomes but impaired the directionality of their long-range movements. The production of a nonfunctional domain of MMIα impaired the intracellular distribution of lysosomes and the directionality of their long-range movements. Altogether, our observations indicate for the first time that both actin filaments and MMIα contribute to the movement of lysosomes in cooperation with microtubules and their associated molecular motors.

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Oiwa, Kazuhiro, R. Kometani, Dong Yang Li, Y. Shitaka, R. Nakamori, S. Matsui und H. Sakakibara. „Molecular and Nanometer-Scale Self-Organized System Generated by Protein Motor Functions“. Materials Science Forum 539-543 (März 2007): 3290–96. http://dx.doi.org/10.4028/www.scientific.net/msf.539-543.3290.

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Creatures have evolved extremely intelligent and complex adaptive systems for conducting their movements. They are protein motors with typical sizes of a few tens of nanometers. Protein motors include three major protein families, myosin, kinesin and dynein, which participate in a wide range of cellular processes, using energy from the hydrolysis of adenosinetriphosphate ATP. To harness these protein motors to power nanometer-scale devices, we have investigated effective and non-destructive methods for immobilizing protein motors on surfaces and to arrange the output of these motors, e.g. force and movement, to be in a defined direction. We found NEB-22 to be useful for retaining the abilities of protein motors to support the movement of protein filaments. We fabricated various patterns of tracks of NEB-22 on coverslips and protein motors were introduced and immobilized on glass surface. The trajectories of protein polymers were confined to these tracks. Simple patterns readily biased and guide polymer movement confining it to be unidirectional. In addition, having used dynein c purified from Chlamydomonas flagellar axoneme, we showed that microtubules driven by surface-bound dynein were self-organized into dynamic streams through collisions between the microtubules and their subsequent joining.

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Arif, Ehtesham, Pankaj Sharma, Ashish Solanki, Leena Mallik, Yogendra S. Rathore, Waleed O. Twal, Samir K. Nath et al. „Structural Analysis of the Myo1c and Neph1 Complex Provides Insight into the Intracellular Movement of Neph1“. Molecular and Cellular Biology 36, Nr. 11 (04.04.2016): 1639–54. http://dx.doi.org/10.1128/mcb.00020-16.

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The Myo1c motor functions as a cargo transporter supporting various cellular events, including vesicular trafficking, cell migration, and stereociliary movements of hair cells. Although its partial crystal structures were recently described, the structural details of its interaction with cargo proteins remain unknown. This study presents the first structural demonstration of a cargo protein, Neph1, attached to Myo1c, providing novel insights into the role of Myo1c in intracellular movements of this critical slit diaphragm protein. Using small angle X-ray scattering studies, models of predominant solution conformation of unliganded full-length Myo1c and Myo1c bound to Neph1 were constructed. The resulting structures show an extended S-shaped Myo1c with Neph1 attached to its C-terminal tail. Importantly, binding of Neph1 did not induce a significant shape change in Myo1c, indicating this as a spontaneous process or event. Analysis of interaction surfaces led to the identification of a critical residue in Neph1 involved in binding to Myo1c. Indeed, a point mutant from this site abolished interaction between Neph1 and Myo1c when tested in thein vitroand in live-cell binding assays. Live-cell imaging, including fluorescence recovery after photobleaching, provided further support for the role of Myo1c in intracellular vesicular movement of Neph1 and its turnover at the membrane.

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Dougherty, Kevin, und Manuel Covarrubias. „A Dipeptidyl Aminopeptidase–like Protein Remodels Gating Charge Dynamics in Kv4.2 Channels“. Journal of General Physiology 128, Nr. 6 (27.11.2006): 745–53. http://dx.doi.org/10.1085/jgp.200609668.

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Dipeptidyl aminopeptidase–like proteins (DPLPs) interact with Kv4 channels and thereby induce a profound remodeling of activation and inactivation gating. DPLPs are constitutive components of the neuronal Kv4 channel complex, and recent observations have suggested the critical functional role of the single transmembrane segment of these proteins (Zagha, E., A. Ozaita, S.Y. Chang, M.S. Nadal, U. Lin, M.J. Saganich, T. McCormack, K.O. Akinsanya, S.Y. Qi, and B. Rudy. 2005. J. Biol. Chem. 280:18853–18861). However, the underlying mechanism of action is unknown. We hypothesized that a unique interaction between the Kv4.2 channel and a DPLP found in brain (DPPX-S) may remodel the channel's voltage-sensing domain. To test this hypothesis, we implemented a robust experimental system to measure Kv4.2 gating currents and study gating charge dynamics in the absence and presence of DPPX-S. The results demonstrated that coexpression of Kv4.2 and DPPX-S causes a −26 mV parallel shift in the gating charge-voltage (Q-V) relationship. This shift is associated with faster outward movements of the gating charge over a broad range of relevant membrane potentials and accelerated gating charge return upon repolarization. In sharp contrast, DPPX-S had no effect on gating charge movements of the Shaker B Kv channel. We propose that DPPX-S destabilizes resting and intermediate states in the voltage-dependent activation pathway, which promotes the outward gating charge movement. The remodeling of gating charge dynamics may involve specific protein–protein interactions of the DPPX-S's transmembrane segment with the voltage-sensing and pore domains of the Kv4.2 channel. This mechanism may determine the characteristic fast operation of neuronal Kv4 channels in the subthreshold range of membrane potentials.

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Subramaniam, Srinivasa. „Ribosome traffic jam in neurodegeneration: decoding hurdles in Huntington disease“. Cell Stress 5, Nr. 6 (14.06.2021): 86–88. http://dx.doi.org/10.15698/cst2021.06.251.

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A ribosome typically moves at a particular rate on a given mRNA transcript to decode the nucleic acid information required to synthesize proteins. The speed and directionality of the ribosome movements during mRNA translation are determined by the mRNA sequence and structure and by various decoding factors. However, the molecular mechanisms of this remarkable movement during protein synthesis, or its relevance in brain disorders, remain unknown. Recent studies have indicated that defects in protein synthesis occur in various neurodegenerative diseases, but the mechanistic details are unclear. This is a major problem because identifying the factors that determine protein synthesis defects may offer new avenues for developing therapeutic remedies for currently incurable diseases like neurodegenerative disorders. Based on our recent study (Eshraghi et al., Nat Commun 12(1):1461; doi: 10.1038/s41467-021-21637-y), this short commentary will review the mechanistic understanding of Huntingtin (HTT)-mediated ribosome stalling indicating that central defects in protein synthesis in Huntington disease (HD) are orchestrated by jamming of ribosomes on mRNA transcripts.

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Capano, Michela, und Martin Crompton. „Bax translocates to mitochondria of heart cells during simulated ischaemia: involvement of AMP-activated and p38 mitogen-activated protein kinases“. Biochemical Journal 395, Nr. 1 (15.03.2006): 57–64. http://dx.doi.org/10.1042/bj20051654.

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The cytosolic protein Bax plays a key role in apoptosis by migrating to mitochondria and releasing proapoptotic proteins from the mitochondrial intermembrane space. The present study investigates the movement of Bax in isolated rat neonatal cardiomyocytes subjected to simulated ischaemia (minus glucose, plus cyanide), using green fluorescent protein-tagged Bax as a means of imaging Bax movements. Simulated ischaemia induced Bax translocation from the cytosol to mitochondria, commencing within 20 min of simulated ischaemia and progressing for several hours. Under the same conditions, there was an increase in the active, phosphorylated forms of p38 MAPK (mitogen-activated protein kinase) and AMPK (AMP-activated protein kinase). The AMPK activators AICAR (5-aminoimidazole-4-carboxamide ribonucleoside) and metformin also stimulated Bax translocation. Inhibition of p38 MAPK with SB203580 attenuated the phosphorylation of the downstream substrates, MAPK-activated protein kinases 2 and 3, but not that of the upstream MAPK kinase 3, nor of AMPK. Under all conditions (ischaemia, AICAR and metformin), SB203580 blocked Bax translocation completely. It is concluded that Bax translocation to mitochondria is an early step in ischaemia and that it occurs in response to activation of p38 MAPK downstream of AMPK.

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Johnson, Ruth I., Alanna Sedgwick, Crislyn D'Souza-Schorey und Ross L. Cagan. „Role for a Cindr–Arf6 axis in patterning emerging epithelia“. Molecular Biology of the Cell 22, Nr. 23 (Dezember 2011): 4513–26. http://dx.doi.org/10.1091/mbc.e11-04-0305.

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Patterning of the Drosophila pupal eye is characterized by precise cell movements. In this paper, we demonstrate that these movements require an Arf regulatory cycle that connects surface receptors to actin-based movement. dArf6 activity—regulated by the Arf GTPase–activating proteins (ArfGAPs) dAsap and dArfGAP3 and the Arf GTP exchange factors Schizo and dPsd—promoted large cellular extensions; time-lapse microscopy indicated that these extensions presage cell rearrangements into correct epithelial niches. During this process, the Drosophila eye also requires interactions between surface Neph1/nephrin adhesion receptors Roughest and Hibris, which bind the adaptor protein Cindr (CD2AP). We provide evidence that Cindr forms a physical complex with dArfGAP3 and dAsap. Our data suggest this interaction sequesters ArfGAP function to liberate active dArf6 elsewhere in the cell. We propose that a Neph1/nephrin–Cindr/ArfGAP complex accumulates to limit local Arf6 activity and stabilize adherens junctions. Our model therefore links surface adhesion via an Arf6 regulatory cascade to dynamic modeling of the cytoskeleton, accounting for precise cell movements that organize the functional retinal field. Further, we demonstrate a similar relationship between the mammalian Cindr orthologue CD2AP and Arf6 activity in cell motility assays. We propose that this Cindr/CD2AP-mediated regulation of Arf6 is a widely used mechanism in emerging epithelia.

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Holzhüter, Katharina, und Eric R. Geertsma. „Functional (un)cooperativity in elevator transport proteins“. Biochemical Society Transactions 48, Nr. 3 (23.06.2020): 1047–55. http://dx.doi.org/10.1042/bst20190970.

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The activity of enzymes is subject to regulation at multiple levels. Cooperativity, the interconnected behavior of active sites within a protein complex, directly affects protein activity. Cooperativity is a mode of regulation that requires neither extrinsic factors nor protein modifications. Instead, it allows enzymes themselves to modulate reaction rates. Cooperativity is an important regulatory mechanism in soluble proteins, but also examples of cooperative membrane proteins have been described. In this review, we summarize the current knowledge on interprotomer cooperativity in elevator-type proteins, a class of membrane transporters characterized by large rigid-body movements perpendicular to the membrane, and highlight well-studied examples and experimental approaches.

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Ko, Dennis C., Michael D. Gordon, Janet Y. Jin und Matthew P. Scott. „Dynamic Movements of Organelles Containing Niemann-Pick C1 Protein: NPC1 Involvement in Late Endocytic Events“. Molecular Biology of the Cell 12, Nr. 3 (März 2001): 601–14. http://dx.doi.org/10.1091/mbc.12.3.601.

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People homozygous for mutations in the Niemann-Pick type C1 (NPC1) gene have physiological defects, including excess accumulation of intracellular cholesterol and other lipids, that lead to drastic neural and liver degeneration. The NPC1 multipass transmembrane protein is resident in late endosomes and lysosomes, but its functions are unknown. We find that organelles containing functional NPC1-fluorescent protein fusions undergo dramatic movements, some in association with extending strands of endoplasmic reticulum. InNPC1 mutant cells the NPC1-bearing organelles that normally move at high speed between perinuclear regions and the periphery of the cell are largely absent. Pulse-chase experiments with dialkylindocarbocyanine low-density lipoprotein showed that NPC1 organelles function late in the endocytic pathway; NPC1 protein may aid the partitioning of endocytic and lysosomal compartments. The close connection between NPC1 and the drug U18666A, which causes NPC1-like organelle defects, was established by rescuing drug-treated cells with overproduced NPC1. U18666A inhibits outward movements of NPC1 organelles, trapping membranes and cholesterol in perinuclear organelles similar to those in NPC1 mutant cells, even when cells are grown in lipoprotein-depleted serum. We conclude that NPC1 protein promotes the creation and/or movement of particular late endosomes, which rapidly transport materials to and from the cell periphery.

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Roos, F. J., A. Zimmermann und H. U. Keller. „Effect of phorbol myristate acetate and the chemotactic peptide fNLPNTL on shape and movement of human neutrophils“. Journal of Cell Science 88, Nr. 3 (01.10.1987): 399–406. http://dx.doi.org/10.1242/jcs.88.3.399.

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The results show that the distinct types of shape produced by phorbol myristate acetate (PMA) and by chemotactic peptides (fNLPNTL) are associated with distinct types of neutrophil movement. Whereas the chemotactic peptide can induce front-tail polarity characterized by an expanding front, a contracted tail and preferential unidirectional movements of intracellular organelles, PMA can only elicit non-polar movements characterized by random formation and retraction of projections all over the surface, intracellular movements of organelles being ill-defined and changing in direction. Combined stimulation of human neutrophils with PMA and fNLPNTL results in a suppression of peptide-induced polarity and the formation of non-polar motile cells resembling those stimulated with PMA alone. The results suggest that the diacylglycerol-protein kinase C pathway may be instrumental in transducing or modulating signals to the locomotor apparatus of the cell. PMA-treated cells are, however, still capable of developing directional responses when appropriately stimulated. The findings lead to the hypothesis that distinct types of neutrophil movements are preferentially associated with distinct functions.

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Kondo, Hiroko X., Noriaki Okimoto, Gentaro Morimoto und Makoto Taiji. „Free-Energy Landscapes of Protein Domain Movements upon Ligand Binding“. Journal of Physical Chemistry B 115, Nr. 23 (16.06.2011): 7629–36. http://dx.doi.org/10.1021/jp111902t.

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Spudich, John L. „Transducer protein HtrI controls proton movements in sensory rhodopsin I“. Biophysical Chemistry 56, Nr. 1-2 (September 1995): 165–69. http://dx.doi.org/10.1016/0301-4622(95)00029-w.

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Qi, G., R. Lee und S. Hayward. „A comprehensive and non-redundant database of protein domain movements“. Bioinformatics 21, Nr. 12 (31.03.2005): 2832–38. http://dx.doi.org/10.1093/bioinformatics/bti420.

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Song, Byung-Ho, Sun-Cheol Choi und Jin-Kwan Han. „Local activation of protein kinase A inhibits morphogenetic movements duringXenopusgastrulation“. Developmental Dynamics 227, Nr. 1 (Mai 2003): 91–103. http://dx.doi.org/10.1002/dvdy.10296.

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Orellana, Laura. „Are Protein Shape-Encoded Lowest-Frequency Motions a Key Phenotype Selected by Evolution?“ Applied Sciences 13, Nr. 11 (01.06.2023): 6756. http://dx.doi.org/10.3390/app13116756.

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At the very deepest molecular level, the mechanisms of life depend on the operation of proteins, the so-called “workhorses” of the cell. Proteins are nanoscale machines that transform energy into useful cellular work, such as ion or nutrient transport, information processing, or energy transformation. Behind every biological task, there is a nanometer-sized molecule whose shape and intrinsic motions, binding, and sensing properties have been evolutionarily polished for billions of years. With the emergence of structural biology, the most crucial property of biomolecules was thought to be their 3D shape, but how this relates to function was unclear. During the past years, Elastic Network Models have revealed that protein shape, motion and function are deeply intertwined, so that each structure displays robustly shape-encoded functional movements that can be extraordinarily conserved across the tree of life. Here, we briefly review the growing literature exploring the interplay between sequence evolution, protein shape, intrinsic motions and function, and highlight examples from our research in which fundamental movements are conserved from bacteria to mammals or selected by cancer cells to modulate function.

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Mueller, Maria. „Light-induced Helix Movements in Channelrhodopsin-2“. Acta Crystallographica Section A Foundations and Advances 70, a1 (05.08.2014): C1067. http://dx.doi.org/10.1107/s2053273314089323.

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Electron crystallography has the unique advantage of visualizing membrane proteins in a native-like lipid environment, which likely favors the native conformation. In addition, it allows for the protein to undergo conformational changes in response to their activating signals. We used 2D crystals of channelrhodopsin-2, a cation-selective light-gated channel from Chlamydomonas reinhardtii (Nagel et al., 2003) to study light-induced conformational changes of this intriguing channel, which is currently a powerful tool in optogenetics. Therefore, 2D crystals of the slow photocycling C128T ChR2 mutant were exposed to 473 nm light and rapidly frozen to trap the open state. Projection difference maps at 6 Å resolution show the location, extent and direction of light-induced conformational changes in ChR2 during the transition from the closed state to the ion-conducting open state. Difference peaks indicate that transmembrane helices (TMHs) 2, 6, and 7 reorient or rearrange during the photocycle. No major differences were found near TMH3 and 4 at the dimer interface. While conformational changes in TMH6 and 7 are known from other microbial-type rhodopsins, our results indicate that TMH2 has a key role in light-induced channel opening and closing in ChR2.

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Renkin, E. M. „Some consequences of capillary permeability to macromolecules: Starling's hypothesis reconsidered“. American Journal of Physiology-Heart and Circulatory Physiology 250, Nr. 5 (01.05.1986): H706—H710. http://dx.doi.org/10.1152/ajpheart.1986.250.5.h706.

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Starling's hypothesis ascribes fluid movements across capillary walls to the interaction of hydrostatic and colloid osmotic forces. For 90 years it has been recognized as the basis of plasma-to-interstitial fluid balance. Its original statement was based on the notion of capillary impermeability to plasma proteins. However, as knowledge of transcapillary exchange of plasma proteins developed, its formulation was progressively modified to allow for protein transport and for interaction of protein transport with volume flow. The most important aspects of the conceptual evolution of Starling's hypothesis are reviewed in the text of this lecture.

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Wolniak, Stephen M. „The regulation of mitotic spindle function“. Biochemistry and Cell Biology 66, Nr. 6 (01.06.1988): 490–514. http://dx.doi.org/10.1139/o88-061.

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The process of mitosis includes a series of morphological changes in the cell in which the directional movements of chromosomes are the most prominent. The presence of a microtubular array, known as the spindle or mitotic apparatus, provides at least a scaffold upon which these movements take place. The precise mechanism for chromosome movement remains obscure, but new findings suggest that the kinetochore may play a key role in chromosome movement toward the spindle pole, and that sliding interactions between or among adjacent microtubules may provide the mechanochemical basis for spindle elongation. The physiological regulation of the anaphase motors and of spindle operation either before or after anaphase remains equally elusive. Elicitors that may serve as controlling elements in spindle function include shifts in cytosolic calcium activity and perhaps the activation or inactivation of protein kinases, which in turn produce changes in the state of phosphorylation of specific spindle components.

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Su, Wen-Hong, Hsiun-ing Chen und Chauying J. Jen. „Differential movements of VE-cadherin and PECAM-1 during transmigration of polymorphonuclear leukocytes through human umbilical vein endothelium“. Blood 100, Nr. 10 (15.11.2002): 3597–603. http://dx.doi.org/10.1182/blood-2002-01-0303.

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Most existing evidence regarding junction protein movements during transendothelial migration of leukocytes comes from taking postfixation snap shots of the transendothelial migration process that happens on a cultured endothelial monolayer. In this study, we used junction protein–specific antibodies that did not interfere with the transendothelial migration to examine the real-time movements of vascular endothelial–cadherin (VE-cadherin) and platelet/endothelial cell adhesion molecule-1 (PECAM-1) during transmigration of polymorphonuclear leukocytes (PMNs) either through a cultured endothelial monolayer or through the endothelium of dissected human umbilical vein tissue. In either experimental model system, both junction proteins showed relative movements, not transient disappearance, at the PMN transmigration sites. VE-cadherin moved away to different ends of the transmigration site, whereas PECAM-1 opened to surround the periphery of a transmigrating PMN. Junction proteins usually moved back to their original positions when the PMN transmigration process was completed in less than 2 minutes. The relative positions of some junction proteins might rearrange to form a new interendothelial contour after PMNs had transmigrated through multicellular corners. Although transmigrated PMNs maintained good mobility, they only moved laterally underneath the vascular endothelium instead of deeply into the vascular tissue. In conclusion, our results obtained from using either cultured cells or vascular tissues showed that VE-cadherin–containing adherent junctions were relocated aside, not opened or disrupted, whereas PECAM-1–containing junctions were opened during PMN transendothelial migration.

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Campbell, Edward M., Mark P. Dodding, Melvyn W. Yap, Xiaolu Wu, Sarah Gallois-Montbrun, Michael H. Malim, Jonathan P. Stoye und Thomas J. Hope. „TRIM5α Cytoplasmic Bodies Are Highly Dynamic Structures“. Molecular Biology of the Cell 18, Nr. 6 (Juni 2007): 2102–11. http://dx.doi.org/10.1091/mbc.e06-12-1075.

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Tripartite motif (TRIM)5α has recently been identified as a host restriction factor that has the ability to block infection by certain retroviruses in a species-dependent manner. One interesting feature of this protein is that it is localized in distinct cytoplasmic clusters designated as cytoplasmic bodies. The potential role of these cytoplasmic bodies in TRIM5α function remains to be defined. By using fluorescent fusion proteins and live cell microscopy, we studied the localization and dynamics of TRIM5α cytoplasmic bodies. This analysis reveals that cytoplasmic bodies are highly mobile, exhibiting both short saltatory movements and unidirectional long-distance movements along the microtubule network. The morphology of the cytoplasmic bodies is also dynamic. Finally, photobleaching and photoactivation analysis reveals that the TRIM5α protein present in the cytoplasmic bodies is very dynamic, rapidly exchanging between cytoplasmic bodies and a more diffuse cytoplasmic population. Therefore, TRIM5α cytoplasmic bodies are dynamic structures more consistent with a role in function or regulation rather than protein aggregates or inclusion bodies that represent dead-end static structures.

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Hoepfner, Dominic, Marlene van den Berg, Peter Philippsen, Henk F. Tabak und Ewald H. Hettema. „A role for Vps1p, actin, and the Myo2p motor in peroxisome abundance and inheritance in Saccharomyces cerevisiae“. Journal of Cell Biology 155, Nr. 6 (03.12.2001): 979–90. http://dx.doi.org/10.1083/jcb.200107028.

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In vivo time-lapse microscopy reveals that the number of peroxisomes in Saccharomyces cerevisiae cells is fairly constant and that a subset of the organelles are targeted and segregated to the bud in a highly ordered, vectorial process. The dynamin-like protein Vps1p controls the number of peroxisomes, since in a vps1Δ mutant only one or two giant peroxisomes remain. Analogous to the function of other dynamin-related proteins, Vps1p may be involved in a membrane fission event that is required for the regulation of peroxisome abundance. We found that efficient segregation of peroxisomes from mother to bud is dependent on the actin cytoskeleton, and active movement of peroxisomes along actin filaments is driven by the class V myosin motor protein, Myo2p: (a) peroxisomal dynamics always paralleled the polarity of the actin cytoskeleton, (b) double labeling of peroxisomes and actin cables revealed a close association between both, (c) depolymerization of the actin cytoskeleton abolished all peroxisomal movements, and (d) in cells containing thermosensitive alleles of MYO2, all peroxisome movement immediately stopped at the nonpermissive temperature. In addition, time-lapse videos showing peroxisome movement in wild-type and vps1Δ cells suggest the existence of various levels of control involved in the partitioning of peroxisomes.

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Voilquin, Laetitia, Massimo Lodi, Thomas Di Mattia, Marie-Pierre Chenard, Carole Mathelin, Fabien Alpy und Catherine Tomasetto. „STARD3: A Swiss Army Knife for Intracellular Cholesterol Transport“. Contact 2 (Januar 2019): 251525641985673. http://dx.doi.org/10.1177/2515256419856730.

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Intracellular cholesterol transport is a complex process involving specific carrier proteins. Cholesterol-binding proteins, such as the lipid transfer protein steroidogenic acute regulatory-related lipid transfer domain-3 (STARD3), are implicated in cholesterol movements between organelles. Indeed, STARD3 modulates intracellular cholesterol allocation by reducing it from the plasma membrane and favoring its passage from the endoplasmic reticulum (ER) to endosomes, where the protein is localized. STARD3 interacts with ER-anchored partners, notably vesicle-associated membrane protein-associated proteins (VAP-A and VAP-B) and motile sperm domain-containing 2 (MOSPD2), to create ER–endosome membrane contacts. Mechanistic studies showed that at ER–endosome contacts, STARD3 and VAP proteins build a molecular machine able to rapidly transfer cholesterol. This review presents the current knowledge on the molecular and cellular function of STARD3 in intracellular cholesterol traffic.

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Perestenko, P., M. C. Ashby und J. M. Henley. „Real-time imaging of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPA receptor) movements in neurons“. Biochemical Society Transactions 31, Nr. 4 (01.08.2003): 880–84. http://dx.doi.org/10.1042/bst0310880.

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The mechanisms that regulate α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) synthesis, transport, targeting and surface expression are of fundamental importance for fast excitatory neurotransmission and synaptic plasticity in the mammalian central nervous system. It has become apparent that these control processes involve complex sets of protein–protein interactions and many of the proteins responsible have been identified. We have been working to visualize AMPAR movement in living neurons in order to investigate the effects of blocking protein interactions. Here we outline the approaches used and the results obtained thus far.

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MILLER, ARIA M., TERESA RAMIREZ, FREDDI I. ZUNIGA, GINA H. OCHOA, SHAUNTE GRAY, SHANNON D. KELLY, BRIAN MATSUMOTO und LAURA J. ROBLES. „Rho GTPases regulate rhabdom morphology in octopus photoreceptors“. Visual Neuroscience 22, Nr. 3 (Mai 2005): 295–304. http://dx.doi.org/10.1017/s0952523805223052.

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In the cephalopod retina, light/dark adaptation is accompanied by a decrease/increase in rhabdom size and redistribution of rhodopsin and retinochrome. Rearrangements in the actin cytoskeleton probably govern changes in rhabdom size by regulating the degradation/formation of rhabdomere microvilli. Photopigment movements may be directed by microtubules present in the outer segment core cytoplasm. We believe that rhodopsin activation by light stimulates Rho and Rac signaling pathways, affecting these cytoskeletal systems and their possible functions in controlling rhabdom morphology and protein movements. In this study, we localized cytoskeletal and signaling proteins in octopus photoreceptors to determine their concurrence between the lighting conditions. We used toxin B fromClostridium difficileto inhibit the activity of Rho/Rac and observed its effect on the location of signaling proteins and actin and tubulin. In both lighting conditions, we found Rho in specific sets of juxtaposed rhabdomeres in embryonic and adult retinas. In the light, Rho and actin were localized along the length of the rhabdomere, but, in the dark, both proteins were absent from a space beneath the inner limiting membrane. Rac colocalized with tubulin in the outer segment core cytoplasm and, like Rho, the two proteins were also absent beneath the inner limiting membrane in the dark. The distribution of actin and Rho was affected by toxin B and, in dark-adapted retinas, actin and Rho distribution was similar to that observed in the light. Our results suggest that the Rho/Rac GTPases are candidates for the regulation of rhabdomere size and protein movements in light-dark-adapted octopus photoreceptors.

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