Institute For Biophysikalische Chemie

OE, Germany

Institute For Biophysikalische Chemie

OE, Germany
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Rai A.,Institute For Biophysikalische Chemie | Nothe H.,Max Planck Institute For Medizinische Forschung | Tzvetkov N.,Institute For Biophysikalische Chemie | Korenbaum E.,Forschungseinrichtung fur Strukturanalyse | And 3 more authors.
Cellular and Molecular Life Sciences | Year: 2011

Dictyostelium discoideum cells produce five dynamin family proteins. Here, we show that dynamin B is the only member of this group of proteins that is initially produced as a preprotein and requires processing by mitochondrial proteases for formation of the mature protein. Our results show that dynamin B-depletion affects many aspects of cell motility, cell-cell and cell-surface adhesion, resistance to osmotic shock, and fatty acid metabolism. The mature form of dynamin B mediates a wide range and unique combination of functions. Dynamin B affects events at the plasma membrane, peroxisomes, the contractile vacuole system, components of the actin-based cytoskeleton, and cell adhesion sites. The modulating effect of dynamin B on the activity of the contractile vacuole system is unique for the Dictyostelium system. Other functions displayed by dynamin B are commonly associated with either classical dynamins or dynamin-related proteins. © The Author(s) 2010.

Brinkmann K.,University of Munster | Winterhoff M.,Institute For Biophysikalische Chemie | Onel S.-F.,University of Marburg | Schultz J.,University of Würzburg | And 2 more authors.
Journal of Cell Science | Year: 2016

Wiskott-Aldrich syndrome proteins (WASPs) are nucleationpromoting factors (NPF) that differentially control the Arp2/3 complex. In Drosophila, three different family members, SCAR (also known asWAVE),WASP andWASH (also known as CG13176), have been analyzed so far. Here, we characterized WHAMY, the fourth Drosophila WASP family member. whamy originated from a wasp gene duplication and underwent a sub-neofunctionalization. Unlike WASP, we found that WHAMY specifically interacted with activated Rac1 through its two CRIB domains, which were sufficient for targeting WHAMY to lamellipodial and filopodial tips. Biochemical analyses showed that WHAMY promoted exceptionally fast actin filament elongation, although it did not activate the Arp2/3 complex. Loss- and gain-of-function studies revealed an important function of WHAMY in membrane protrusions and cell migration in macrophages. Genetic data further implied synergistic functions between WHAMY and WASP during morphogenesis. Double mutants were late-embryonic lethal and showed severe defects in myoblast fusion. Trans-heterozygous mutant animals showed strongly increased defects in sensory cell fate specification. Thus, WHAMY is a novel actin polymerase with an initial partitioning of ancestral WASP functions in development and subsequent acquisition of a new function in cell motility during evolution.

Reubold T.F.,Institute For Biophysikalische Chemie | Faelber K.,Max Delbruck Centrum fur Molekulare Medizin | Plattner N.,Free University of Berlin | Posor Y.,Leibniz Institute for Molecular Pharmacology | And 12 more authors.
Nature | Year: 2015

The mechanochemical protein dynamin is the prototype of the dynamin superfamily of large GTPases, which shape and remodel membranes in diverse cellular processes. Dynamin forms predominantly tetramers in the cytosol, which oligomerize at the neck of clathrin-coated vesicles to mediate constriction and subsequent scission of the membrane. Previous studies have described the architecture of dynamin dimers, but the molecular determinants for dynamin assembly and its regulation have remained unclear. Here we present the crystal structure of the human dynamin tetramer in the nucleotide-free state. Combining structural data with mutational studies, oligomerization measurements and Markov state models of molecular dynamics simulations, we suggest a mechanism by which oligomerization of dynamin is linked to the release of intramolecular autoinhibitory interactions. We elucidate how mutations that interfere with tetramer formation and autoinhibition can lead to the congenital muscle disorders Charcot-Marie-Tooth neuropathy and centronuclear myopathy, respectively. Notably, the bent shape of the tetramer explains how dynamin assembles into a right-handed helical oligomer of defined diameter, which has direct implications for its function in membrane constriction. ©2015 Macmillan Publishers Limited. All rights reserved.

Tischer A.,Mayo Medical School | Pultke H.,Scil Proteins | Topf A.,Institute For Biophysikalische Chemie | Auton M.,Mayo Medical School | And 2 more authors.
FEBS Journal | Year: 2014

The ionic liquid N-ethyl-N′-methyl imidazolium chloride (EMIMCl) has been described as being very efficient in promoting refolding of the recombinant plasminogen activator rPA. Our study reveals that molar concentrations of EMIMCl increase the solubility of native and unfolded proteins due to favorable interactions with amino acid side chains rather than favorably interacting with the peptide backbone. This delicate balance of favorable interactions with side chains and unfavorable interactions with the peptide backbone provides a molecular explanation of how EMIMCl suppresses protein aggregation and simultaneously promotes refolding. By contrast, high concentrations of EMIMCl denature proteins because of a reduced water content and strong favorable interactions with amino acid side chains. This denatured species is not soluble and aggregates because, in contrast to the classical denaturants, guanidine hydrochloride and urea, EMIMCl does not solubilize the peptide backbone. Structured digital abstract PNP and PNP bind by molecular sieving (1, 2, 3, 4) The ionic liquid EMIMCl is efficient in promoting the refolding of rPA. Molar concentrations of EMIMCl increase the solubility of native and unfolded proteins due to favorable interactions with amino acid side chains, while the interaction with the peptide backbone is unfavorable. Although a refolding enhancer on one side, high concentrations of EMIMCl result in denaturation and aggregation of proteins. © 2014 FEBS.

Heissler S.M.,Institute For Biophysikalische Chemie | Manstein D.J.,Institute For Biophysikalische Chemie
Cellular and Molecular Life Sciences | Year: 2012

Myosin-7a participates in auditory and visual processes. Defects in MYO7A, the gene encoding the myosin-7a heavy chain, are causative for Usher syndrome 1B, the most frequent cause of deaf-blindness in humans. In the present study, we performed a detailed kinetic and functional characterization of the isolated human myosin-7a motor domain to elucidate the details of chemomechanical coupling and the regulation of motor function. A rate-limiting, slow ADP release step causes long lifetimes of strong actin-binding intermediates and results in a high duty ratio. Moreover, our results reveal a Mg 2+-sensitive regulatory mechanism tuning the kinetic and mechanical properties of the myosin-7a motor domain. We obtained direct evidence that changes in the concentration of free Mg 2+ ions affect the motor properties of human myosin-7a using an in vitro motility assay system. Our results suggest that in a cellular environment, compartment-specific fluctuations in free Mg 2+ ions can mediate the conditional switching of myosin-7a between cargo moving and tension bearing modes. © 2011 The Author(s).

Diensthuber R.P.,Institute For Biophysikalische Chemie | Muller M.,Institute For Biophysikalische Chemie | Heissler S.M.,Institute For Biophysikalische Chemie | Taft M.H.,Institute For Biophysikalische Chemie | And 2 more authors.
FEBS Letters | Year: 2011

Phalloidin and fluorescently labeled phalloidin analogs are established reagents to stabilize and mark actin filaments for the investigation of acto-myosin interactions. In the present study, we employed transient and steady-state kinetic measurements as well as in vitro motility assays to show that phalloidin perturbs the productive interaction of human non-muscle myosin-2A and -2C1 with filamentous actin. Phalloidin binding to F-actin results in faster dissociation of the complex formed with non-muscle myosin-2A and -2C1, reduced actin-activated ATP turnover, and slower velocity of actin filaments in the in vitro motility assay. In contrast, phalloidin binding to F-actin does not affect the interaction with human non-muscle myosin isoform 2B and Dictyostelium myosin-2 and myosin-5b. © 2011 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

Tsiavaliaris G.,Institute For Biophysikalische Chemie | Itel F.,University of Basel | Hedfalk K.,Gothenburg University | Al-Samir S.,AG Vegetative Physiologie 4220 | And 3 more authors.
FASEB Journal | Year: 2015

Here we ask the following: 1) what is the CO2 permeability (Pco2) of unilamellar liposomes composed of l-α-phosphatidylcholine (PC)/l-α-phosphatidylserine (PS) =4:1 and containing cholesterol (Chol) at levels often occurring in biologic membranes (50 mol%), and 2) does incorporation of the CO2 channel aquaporin (AQP)1 cause a significant increase in membrane Pco2? Presently, a drastic discrepancy exists between the answers to these two questions obtained from mass-spectrometric 18O-exchange measurements (Chol reduces Pco2100-fold, AQP1 increases Pco2 10-fold) vs.from stopped-flow approaches observing CO2 uptake (no effects of either Chol or AQP1). A novel theory of CO2 uptake by vesicles predicts that in a stopped-flow apparatus this fast process can only be resolved temporally and interpreted quantitatively, if 1) a very low CO2 partial pressure (pCO2) is used (e.g., 18 mmHg), and 2) intravesicular carbonic anhydrase (CA) activity is precisely known. With these prerequisites fulfilled, we find by stopped-flow that 1) Chol-containing vesicles possess a Pco2 = 0.01cm/s, and Chol-free vesicles exhibit ∼1 cm/s, and 2) the Pco2 of 0.01 cm/s is increased ≥ 10-fold by AQP1. Both results agree with previous mass-spectrometric results and thus resolve the apparent discrepancy between the two techniques. We confirm that biologic membranes have an intrinsically low Pco2 that can be raised when functionally necessary by incorporating protein-gas channels such as AQP1. © FASEB.

Yan S.,University of Gottingen | Lv Z.,University of Gottingen | Winterhoff M.,Institute For Biophysikalische Chemie | Wenzl C.,University of Gottingen | And 4 more authors.
Journal of Cell Science | Year: 2013

During Drosophila embryogenesis, the first epithelium with defined cortical compartments is established during cellularization. Actin polymerization is required for the separation of lateral and basal domains as well as suppression of tubular extensions in the basal domain. The actin nucleator mediating this function is unknown. We found that the formin Diaphanous (Dia) is required for establishing and maintaining distinct lateral and basal domains during cellularization. In dia mutant embryos lateral marker proteins, such as Discs-large and Armadillo/b-Catenin spread into the basal compartment. Furthermore, high-resolution and live-imaging analysis of dia mutant embryos revealed an increased number of membrane extensions and endocytic activity at the basal domain, indicating a suppressing function of dia on membrane invaginations. Dia function might be based on an antagonistic interaction with the F-BAR protein Cip4/Toca-1, a known activator of the WASP/WAVE-Arp2/3 pathway. Dia and Cip4 physically and functionally interact and overexpression of Cip4 phenocopies dia loss-of-function. In vitro, Cip4 inhibits mainly actin nucleation by Dia. Thus, our data support a model in which linear actin filaments induced by Dia stabilize cortical compartmentalization by antagonizing membrane turnover induced by WASP/WAVE-Arp2/3 © 2013.

PubMed | Institute For Biophysikalische Chemie, German Electron Synchrotron and Institute For Molekularbiologie
Type: Journal Article | Journal: Genetics | Year: 2016

The highly conserved Notch-signaling pathway mediates cell-to-cell communication and is pivotal for multiple developmental processes and tissue homeostasis in adult organisms. Notch receptors and their ligands are transmembrane proteins with multiple epidermal-growth-factor-like (EGF) repeats in their extracellular domains. In vitro the EGF repeats of mammalian ligands that are essential for Notch activation have been defined. However, in vivo the significance of the structural integrity of each EGF repeat in the ligand ectodomain for ligand function is still unclear. Here, we analyzed the mouse Notch ligand DLL1. We expressed DLL1 proteins with mutations disrupting disulfide bridges in each individual EGF repeat from single-copy transgenes in the HPRT locus of embryonic stem cells. In Notch transactivation assays all mutations impinged on DLL1 function and affected both NOTCH1 and NOTCH2 receptors similarly. An allelic series in mice that carried the same point mutations in endogenous Dll1, generated using a mini-gene strategy, showed that early developmental processes depending on DLL1-mediated NOTCH activation were differently sensitive to mutation of individual EGF repeats in DLL1. Notably, some mutations affected only somite patterning and resulted in vertebral column defects resembling spondylocostal dysostosis. In conclusion, the structural integrity of each individual EGF repeat in the extracellular domain of DLL1 is necessary for full DLL1 activity, and certain mutations in Dll1 might contribute to spondylocostal dysostosis in humans.

Fonfara I.,Justus Liebig University | Curth U.,Institute For Biophysikalische Chemie | Pingoud A.,Justus Liebig University | Wende W.,Justus Liebig University
Nucleic Acids Research | Year: 2012

Zinc-finger nucleases and TALE nucleases are produced by combining a specific DNA-binding module and a non-specific DNA-cleavage module, resulting in nucleases able to cleave DNA at a unique sequence. Here a new approach for creating highly specific nucleases was pursued by fusing a catalytically inactive variant of the homing endonuclease I-SceI, as DNA binding-module, to the type IIP restriction enzyme PvuII, as cleavage module. The fusion enzymes were designed to recognize a composite site comprising the recognition site of PvuII flanked by the recognition site of I-SceI. In order to reduce activity on PvuII sites lacking the flanking I-SceI sites, the enzymes were optimized so that the binding of I-SceI to its sites positions PvuII for cleavage of the composite site. This was achieved by optimization of the linker and by introducing amino acid substitutions in PvuII which decrease its activity or disturb its dimer interface. The most specific variant showed a more than 1000-fold preference for the addressed composite site over an unaddressed PvuII site. These results indicate that using a specific restriction enzyme, such as PvuII, as cleavage module, offers an alternative to the otherwise often used catalytic domain of FokI, which by itself does not contribute to the specificity of the engineered nuclease. © The Author(s) 2011. Published by Oxford University Press.

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