scholarly journals Tumor protein D54 binds intracellular nanovesicles via an amphipathic lipid packing sensor (ALPS) motif

2021 ◽  
Author(s):  
Antoine Reynaud ◽  
Maud Magdeleine ◽  
Amanda Patel ◽  
Anne Sophie Gay ◽  
Delphine Debayle ◽  
...  
Keyword(s):  
Lipid Membranes ◽  
Structural Changes ◽  
Covalent Binding ◽  
Limited Proteolysis ◽  
Coiled Coil ◽  
Tryptophan Fluorescence ◽  
Cd Spectroscopy ◽  
Dependent Manner ◽  
Lipid Packing ◽  
Physicochemical Features

AbstractTumor Protein D54 (TPD54) is an abundant cytosolic protein that belongs to the TPD52 family, a family of four proteins (TPD52, 53, 54 and 55) that are overexpressed in several cancer cells. Even though the functions of these proteins remain elusive, recent investigations indicate that TPD54 binds to very small cytosolic vesicles with a diameter of ca. 30 nm, half the size of classical transport vesicles (e.g. COPI and COPII). Here, we investigated the mechanism of intracellular nanovesicle capture by TPD54. Bioinformatical analysis suggests that TPD54 contains a small coiled-coil followed by several amphipathic helices, which could fold upon binding to lipid membranes. One of these helices has the physicochemical features of an Amphipathic Lipid Packing Sensor (ALPS) motif, which, in other proteins, enables membrane binding in a curvature-dependent manner. Limited proteolysis, CD spectroscopy, tryptophan fluorescence and cysteine mutagenesis coupled to covalent binding of a membrane sensitive probe show that binding of TPD54 to small liposomes is accompanied by large structural changes in the amphipathic helix region. TPD54 binding to artificial liposomes is very sensitive to liposome size and to lipid unsaturation but is poorly dependent on lipid charge. Cellular investigations confirmed the key role of the ALPS motif in vesicle targeting. Surprisingly, the vesicles selected by TPD54 poorly overlap with those captured by the golgin GMAP-210, a long vesicle tether at the Golgi apparatus, which displays a dimeric coiled-coil architecture and an N-terminal ALPS motif. We propose that TPD54 recognizes nanovesicles through a combination of ALPS-dependent and -independent mechanisms.

scholarly journals Effect of cosolvents (polyols) on structural and foaming properties of soy protein isolate  

2017 ◽  
Vol 35 (No. 1) ◽  
pp. 57-66 ◽  
Author(s):  
Pan Mingzhe ◽  
Meng Xianjun ◽  
Jiang Lianzhou ◽  
Yu Dianyu ◽  
Liu Tianyi
Keyword(s):  
Soy Protein ◽  
Structural Changes ◽  
Foam Stability ◽  
Soy Protein Isolate ◽  
Tryptophan Fluorescence ◽  
Surface Hydrophobicity ◽  
Cd Spectroscopy ◽  
Protein Isolate ◽  
Foaming Properties ◽  
Intrinsic Tryptophan Fluorescence

Effect of polyols (mannitol, sorbitol, and xylitol) at three concentrations (5, 10, and 15% w/w) on the structure of soy protein isolates (SPI) was investigated. Changes in foaming properties of SPI were then examined with the addition of polyols at different concentrations. The interactions between SPI and polyols resulted in a substantial decrease in protein surface hydrophobicity and intrinsic tryptophan fluorescence intensity, along with the covering of tyrosine. Furthermore, circular dichroism (CD) spectroscopy of SPI suggested that a more ordered and compact conformation was induced by polyols. Consequently, these structural changes led to lower foamability of SPI. An increase in the viscosity of SPI suspension seemed to be advantageous for improving the foam stability of SPI.

scholarly journals Evidence for a major structural change in Escherichia coli chorismate synthase induced by flavin and substrate binding

1998 ◽  
Vol 335 (2) ◽  
pp. 319-327 ◽  
Author(s):  
Peter MACHEROUX ◽  
Ernst SCHÖNBRUNN ◽  
Dmitri I. SVERGUN ◽  
Vladimir V. VOLKOV ◽  
Michel H. J. KOCH ◽  
...  
Keyword(s):  
Ternary Complex ◽  
Structural Changes ◽  
Tertiary Structure ◽  
Tryptophan Fluorescence ◽  
Cd Spectroscopy ◽  
Scattering Data ◽  
Discrete State ◽  
Chorismate Synthase ◽  
X Ray Scattering ◽  
Ft Ir

Chorismate synthase (EC 4.6.1.4) catalyses the conversion of 5-enolpyruvylshikimate 3-phosphate (EPSP) into chorismate, and requires reduced FMN as a cofactor. The enzyme can bind first oxidized FMN and then EPSP to form a stable ternary complex which does not undergo turnover. This complex can be considered to be a model of the ternary complex between enzyme, EPSP and reduced FMN immediately before catalysis commences. It is shown that the binding of oxidized FMN and EPSP to chorismate synthase affects the properties and structure of the protein. Changes in small-angle X-ray scattering data, decreased susceptibility to tryptic digestion and altered Fourier-transform (FT)-IR spectra provide the first strong evidence for major structural changes in the protein. The tetrameric enzyme undergoes correlated screw movements leading to a more overall compact shape, with no change in oligomerization state. The changes in the FT-IR spectrum appear to reflect changes in the environment of the secondary-structural elements rather than alterations in their distribution, because the far-UV CD spectrum changes very little. Changes in the mobility of the protein during non-denaturing PAGE indicate that the ternary complex may exhibit less conformational flexibility than the apoprotein. Increased enzyme solubility and decreased tryptophan fluorescence are discussed in the light of the observed structural changes. The secondary structure of the enzyme was investigated using far-UV CD spectroscopy, and the tertiary structure was predicted to be an α–β-barrel using discrete state-space modelling.

scholarly journals Structural Effects of Disease-Related Mutations in Actin-Binding Period 3 of Tropomyosin

Molecules ◽  
2021 ◽  
Vol 26 (22) ◽  
pp. 6980
Author(s):  
Balaganesh Kuruba ◽  
Marta Kaczmarek ◽  
Małgorzata Kęsik-Brodacka ◽  
Magdalena Fojutowska ◽  
Małgorzata Śliwinska ◽  
...  
Keyword(s):  
Disulfide Bonds ◽  
Thin Filament ◽  
Structural Changes ◽  
Coiled Coil ◽  
Actin Binding ◽  
Dependent Manner ◽  
Structural Effects ◽  
Coil Structure ◽  
Pointed End ◽  
Cardiomyopathy Mutations

Tropomyosin (Tpm) is an actin-binding coiled-coil protein. In muscle, it regulates contractions in a troponin/Ca2+-dependent manner and controls the thin filament lengths at the pointed end. Due to its size and periodic structure, it is difficult to observe small local structural changes in the coiled coil caused by disease-related mutations. In this study, we designed 97-residue peptides, Tpm1.164–154 and Tpm3.1265–155, focusing on the actin-binding period 3 of two muscle isoforms. Using these peptides, we evaluated the effects of cardiomyopathy mutations: I92T and V95A in Tpm1.1, and congenital myopathy mutations R91P and R91C in Tpm3.12. We introduced a cysteine at the N-terminus of each fragment to promote the formation of the coiled-coil structure by disulfide bonds. Dimerization of the designed peptides was confirmed by gel electrophoresis in the presence and absence of dithiothreitol. Using circular dichroism, we showed that all mutations decreased coiled coil stability, with Tpm3.1265–155R91P and Tpm1.164–154I92T having the most drastic effects. Our experiments also indicated that adding the N-terminal cysteine increased coiled coil stability demonstrating that our design can serve as an effective tool in studying the coiled-coil fragments of various proteins.

scholarly journals The δ subunit and NTPase HelD institute a two-pronged mechanism for RNA polymerase recycling

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Hao-Hong Pei ◽  
Tarek Hilal ◽  
Zhuo A. Chen ◽  
Yong-Heng Huang ◽  
Yuan Gao ◽  
...  
Keyword(s):  
Bacillus Subtilis ◽  
Nucleic Acids ◽  
Rna Polymerase ◽  
Active Site ◽  
Genome Stability ◽  
Slow Growth ◽  
Coiled Coil ◽  
Main Channel ◽  
Dependent Manner ◽  
Secondary Channel

AbstractCellular RNA polymerases (RNAPs) can become trapped on DNA or RNA, threatening genome stability and limiting free enzyme pools, but how RNAP recycling into active states is achieved remains elusive. In Bacillus subtilis, the RNAP δ subunit and NTPase HelD have been implicated in RNAP recycling. We structurally analyzed Bacillus subtilis RNAP-δ-HelD complexes. HelD has two long arms: a Gre cleavage factor-like coiled-coil inserts deep into the RNAP secondary channel, dismantling the active site and displacing RNA, while a unique helical protrusion inserts into the main channel, prying the β and β′ subunits apart and, aided by δ, dislodging DNA. RNAP is recycled when, after releasing trapped nucleic acids, HelD dissociates from the enzyme in an ATP-dependent manner. HelD abundance during slow growth and a dimeric (RNAP-δ-HelD)2 structure that resembles hibernating eukaryotic RNAP I suggest that HelD might also modulate active enzyme pools in response to cellular cues.

scholarly journals New Insights into the Spring-Loaded Conformational Change of Influenza Virus Hemagglutinin

2002 ◽  
Vol 76 (9) ◽  
pp. 4456-4466 ◽  
Author(s):  
Jennifer A. Gruenke ◽  
R. Todd Armstrong ◽  
William W. Newcomb ◽  
Jay C. Brown ◽  
Judith M. White
Keyword(s):  
Influenza Virus ◽  
Conformational Change ◽  
Conformational Changes ◽  
Limited Proteolysis ◽  
Coiled Coil ◽  
Fusion Peptide ◽  
Wild Type ◽  
Influenza Virus Hemagglutinin ◽  
Target Membrane ◽  
Mutant Forms

ABSTRACT Influenza virus hemagglutinin undergoes a conformational change in which a loop-to-helix “spring-loaded” conformational change forms a coiled coil that positions the fusion peptide for interaction with the target bilayer. Previous work has shown that two proline mutations designed to disrupt this change disrupt fusion but did not determine the basis for the fusion defect. In this work, we made six additional mutants with single proline substitutions in the region that undergoes the spring-loaded conformational change and two additional mutants with double proline substitutions in this region. All double mutants were fusion inactive. We analyzed one double mutant, F63P/F70P, as an example. We observed that F63P/F70P undergoes key low-pH-induced conformational changes and binds tightly to target membranes. However, limited proteolysis and electron microscopy observations showed that the mutant forms a coiled coil that is only ∼50% the length of the wild type, suggesting that it is splayed in its N-terminal half. This work further supports the hypothesis that the spring-loaded conformational change is necessary for fusion. Our data also indicate that the spring-loaded conformational change has another role beyond presenting the fusion peptide to the target membrane.

Abstract 201: Generation of Photoactivatable apoA I to Study HDL Transport in vivo Reveals Impaired HDL Recirculation in a Murine Model of Psoriasis

2017 ◽  
Vol 37 (suppl_1) ◽  
Author(s):  
Li-Hao Huang ◽  
Bernd H Zinselmeyer ◽  
Chih-Hao Chang ◽  
Brian T Saunders ◽  
Brian S Kim ◽  
...  
Keyword(s):  
T Cell ◽  
Murine Model ◽  
Structural Changes ◽  
Cardiovascular Outcomes ◽  
Dependent Manner ◽  
Cardiovascular Comorbidity ◽  
Collagen Density

HDL is cardioprotective, but plasma HDL levels do not necessarily predict cardiovascular outcomes. The major HDL-associated protein apoA-I picks up its cholesterol from cells within extravascular compartments to return it to plasma and then bile. Yet, tools are lacking to quantify the important step of HDL transit through extravascular spaces. Here, we developed recombinant photoactivatable apoA-I to quantify endogenous HDL recirculation. Using the tool, we studied HDL passage through skin in healthy mice versus those with experimental psoriasis, wherein collagen density increased in the skin in a CD4 + T cell-dependent manner. In control mice, photoactivated HDL mobilized to plasma within 2 h but was retained in collagen-enriched skin of mice with psoriasis. These data suggest that cardiovascular comorbidity in psoriasis might be linked to T cell-mediated structural changes in skin that impedes systemic recirculation of HDL. This new tool is likely to find wide application in HDL research.

scholarly journals The Structural Integrity of the Model Lipid Membrane during Induced Lipid Peroxidation: The Role of Flavonols in the Inhibition of Lipid Peroxidation

Antioxidants ◽  
2020 ◽  
Vol 9 (5) ◽  
pp. 430 ◽  
Author(s):  
Anja Sadžak ◽  
Janez Mravljak ◽  
Nadica Maltar-Strmečki ◽  
Zoran Arsov ◽  
Goran Baranović ◽  
...  
Keyword(s):  
Lipid Peroxidation ◽  
Lipid Bilayers ◽  
Lipid Membranes ◽  
Structural Changes ◽  
Structural Integrity ◽  
Lipid Membrane ◽  
Membrane Properties ◽  
Structural Reorganization ◽  
Unsaturated Lipids ◽  
Oxidative Attack

The structural integrity, elasticity, and fluidity of lipid membranes are critical for cellular activities such as communication between cells, exocytosis, and endocytosis. Unsaturated lipids, the main components of biological membranes, are particularly susceptible to the oxidative attack of reactive oxygen species. The peroxidation of unsaturated lipids, in our case 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), induces the structural reorganization of the membrane. We have employed a multi-technique approach to analyze typical properties of lipid bilayers, i.e., roughness, thickness, elasticity, and fluidity. We compared the alteration of the membrane properties upon initiated lipid peroxidation and examined the ability of flavonols, namely quercetin (QUE), myricetin (MCE), and myricitrin (MCI) at different molar fractions, to inhibit this change. Using Mass Spectrometry (MS) and Fourier Transform Infrared Spectroscopy (FTIR), we identified various carbonyl products and examined the extent of the reaction. From Atomic Force Microscopy (AFM), Force Spectroscopy (FS), Small Angle X-Ray Scattering (SAXS), and Electron Paramagnetic Resonance (EPR) experiments, we concluded that the membranes with inserted flavonols exhibit resistance against the structural changes induced by the oxidative attack, which is a finding with multiple biological implications. Our approach reveals the interplay between the flavonol molecular structure and the crucial membrane properties under oxidative attack and provides insight into the pathophysiology of cellular oxidative injury.

Characterisation of the conformational changes in platelet factor 4 induced by polyanions: towards in vitro prediction of antigenicity

2014 ◽  
Vol 112 (07) ◽  
pp. 53-64 ◽  
Author(s):  
Sven Brandt ◽  
Krystin Krauel ◽  
Kay E. Gottschalk ◽  
Thomas Renné ◽  
Christiane A. Helm ◽  
...  
Keyword(s):  
Conformational Changes ◽  
Structural Changes ◽  
Cd Spectroscopy ◽  
Platelet Factor 4 ◽  
Drug Induced ◽  
Platelet Factor ◽  
Preclinical Drug Development ◽  
Varying Length ◽  
Endogenous Proteins

SummaryHeparin-induced thrombocytopenia (HIT) is the most frequent drug-induced immune reaction affecting blood cells. Its antigen is formed when the chemokine platelet factor 4 (PF4) complexes with polyanions. By assessing polyanions of varying length and degree of sulfation using immunoassay and circular dichroism (CD)-spectroscopy, we show that PF4 structural changes resulting in antiparallel β-sheet content >30% make PF4/polyanion complexes antigenic. Further, we found that polyphosphates (polyP-55) induce antigenic changes on PF4, whereas fondaparinux does not. We provide a model suggesting that conformational changes exposing antigens on PF4/polyanion complexes occur in the hairpin involving AA 32–38, which form together with C-terminal AA (66–70) of the adjacent PF4 monomer a continuous patch on the PF4 tetramer surface, explaining why only tetrameric PF4 molecules express “HIT antigens”. The correlation of antibody binding in immunoassays with PF4 structural changes provides the intriguing possibility that CD-spectroscopy could become the first antibody-independent, in vitro method to predict potential immunogenicity of drugs. CD-spectroscopy could identify compounds during preclinical drug development that induce PF4 structural changes correlated with antigenicity. The clinical relevance can then be specifically addressed during clinical trials. Whether these findings can be transferred to other endogenous proteins requires further studies.

scholarly journals CAESALPINIA DECAPETALA

2013 ◽  
Vol 20 (03) ◽  
pp. 478-484
Author(s):  
MUHAMMAD KASHIF BAIG ◽  
IRAM IRSHAD ◽  
FAIZA NASEER
Keyword(s):  
Structural Changes ◽  
Ethanol Extract ◽  
Hepatoprotective Activity ◽  
Phytochemical Analysis ◽  
Dependent Manner ◽  
Medical College ◽  
Study Materials ◽  
Sinusoidal Dilatation ◽  
Histopathological Studies ◽  
Animal House

Members of genus Caesalpinia are found world widely in tropical and temperate areas. Caesalpinia species have variouspharmacological actions that include antidiabetic, antiulcer, anticancer, anti-inflammatory, antimicrobial and antirheumatic. Objectives:To assess the Hepatoprotective activity of ethanol extract of Caesalpinia decapetala. Duration of study: September 2012 to November2012. Setting: Pharmacology and Pathology departments of Independent medical college and animal House of university of agriculture,Faisalabad. Study design: Experimental study. Materials and Methods: Hepatoprotective activity was determined by measuring the livermarker enzymes like Bilirubin, AST, ALT and ALK levels and then hepatic biopsy to see any structural changes. Phytochemical analysis ofplant extract indicates that it contains polyphenols and flavonoids that possess antioxidant potential and hence possess Hepatoprotectiveactivity. Results: Liver enzyme levels were significantly raised in rabbits receiving paracetamol and the enzyme levels were significantlyreduced in rabbits who were receiving Caesalpinia Decapetala and paracetamol comparable to silymarin and Paracetamol. Resultsobservation was done in concentration and dose dependent manner. Histopathological studies indicated centrizonal and focal necrosisand ballooning in liver of rabbits treated with paracetamol. It showed only mild steatosis with sinusoidal dilatation and binucleate cells ingroups receiving Caesalpinia decapetala. Conclusions: It is concluded that Caesalpinia decapetala possesses significantHepatoprotective activity.

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