scholarly journals Lipid-bound ApoE3 self-assemble into elliptical disc-shaped particles

2020 ◽  
Author(s):  
Andreas Haahr Larsen ◽  
Nicolai Tidemand Johansen ◽  
Michael Gajhede ◽  
Lise Arleth ◽  
Søren Roi Midtgaard
Keyword(s):  
Lipid Bilayer ◽  
Full Length ◽  
Cholesterol Transport ◽  
X Ray ◽  
Negative Stain ◽  
X Ray Scattering ◽  
Repeat Domain ◽  
Structural Modulation ◽  
Negative Stain Electron Microscopy ◽  
Repeat Segment

AbstractApolipoproteins are vital to lipid metabolism and cholesterol transport in the human body. Here we present a structural study of the lipid-bound particles formed by ApoE3 in a full-length and a truncated version. The particles are formed with, respectively, POPC and DMPC and investigated by small-angle X-ray scattering and negative stain electron microscopy. We find that lipid-bound ApoE3 particles are elliptical, disc-shaped particles composed of a central lipid bilayer encircled by two amphipathic ApoE3 proteins. We went on to investigate a truncated form of ApoE3 containing only residue 80 to 255 (ApoE380-255), which is the central helical repeat segment of ApoE3. The lipid-bound ApoE380-255 particles are found to have the same morphology as the particles with full-length ApoE3. However, they are larger, and form more heterogeneous discoidal structures with four proteins per particle. This behavior is in contrast to ApoA1 where the highly similar helical repeat domain determines the size and stoichiometry of the formed particles both in the case of full-length and truncated ApoA1. Our data hence points towards different mechanisms for lipid bilayer structural modulation by ApoA1 and ApoE3 due to different roles of the non-repeat segments.

scholarly journals The effect of polydispersity, shape fluctuations and curvature on small unilamellar vesicle small-angle X-ray scattering curves

2021 ◽  
Vol 54 (2) ◽  
pp. 557-568
Author(s):  
Veronica Chappa ◽  
Yuliya Smirnova ◽  
Karlo Komorowski ◽  
Marcus Müller ◽  
Tim Salditt
Keyword(s):  
Lipid Bilayer ◽  
Density Profile ◽  
Small Angle ◽  
Thermal Fluctuations ◽  
Electron Density Profile ◽  
Membrane Asymmetry ◽  
X Ray ◽  
X Ray Scattering ◽  
Vesicle Shape ◽  
Small Unilamellar Vesicles

Small unilamellar vesicles (20–100 nm diameter) are model systems for strongly curved lipid membranes, in particular for cell organelles. Routinely, small-angle X-ray scattering (SAXS) is employed to study their size and electron-density profile (EDP). Current SAXS analysis of small unilamellar vesicles (SUVs) often employs a factorization into the structure factor (vesicle shape) and the form factor (lipid bilayer electron-density profile) and invokes additional idealizations: (i) an effective polydispersity distribution of vesicle radii, (ii) a spherical vesicle shape and (iii) an approximate account of membrane asymmetry, a feature particularly relevant for strongly curved membranes. These idealizations do not account for thermal shape fluctuations and also break down for strong salt- or protein-induced deformations, as well as vesicle adhesion and fusion, which complicate the analysis of the lipid bilayer structure. Presented here are simulations of SAXS curves of SUVs with experimentally relevant size, shape and EDPs of the curved bilayer, inferred from coarse-grained simulations and elasticity considerations, to quantify the effects of size polydispersity, thermal fluctuations of the SUV shape and membrane asymmetry. It is observed that the factorization approximation of the scattering intensity holds even for small vesicle radii (∼30 nm). However, the simulations show that, for very small vesicles, a curvature-induced asymmetry arises in the EDP, with sizeable effects on the SAXS curve. It is also demonstrated that thermal fluctuations in shape and the size polydispersity have distinguishable signatures in the SAXS intensity. Polydispersity gives rise to low-q features, whereas thermal fluctuations predominantly affect the scattering at larger q, related to membrane bending rigidity. Finally, it is shown that simulation of fluctuating vesicle ensembles can be used for analysis of experimental SAXS curves.

scholarly journals Lipid Bilayer Structure Determined by the Simultaneous Analysis of Neutron and X-Ray Scattering Data

2008 ◽  
Vol 95 (5) ◽  
pp. 2356-2367 ◽  
Author(s):  
Norbert Kučerka ◽  
John F. Nagle ◽  
Jonathan N. Sachs ◽  
Scott E. Feller ◽  
Jeremy Pencer ◽  
...  
Keyword(s):  
Lipid Bilayer ◽  
Simultaneous Analysis ◽  
Scattering Data ◽  
Bilayer Structure ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

scholarly journals Stability and flexibility of full-length human oligodendrocytic QKI6

2019 ◽  
Vol 12 (1) ◽  
Author(s):  
Arne Raasakka ◽  
Petri Kursula
Keyword(s):  
Rna Binding ◽  
Full Length ◽  
Rna Transport ◽  
Myelin Membrane ◽  
X Ray ◽  
Intrinsically Disordered ◽  
X Ray Scattering ◽  
The Central Nervous System ◽  
Sequential Unfolding

Abstract Objective Oligodendrocytes account for myelination in the central nervous system. During myelin compaction, key proteins are translated in the vicinity of the myelin membrane, requiring targeted mRNA transport. Quaking isoform 6 (QKI6) is a STAR domain-containing RNA transport protein, which binds a conserved motif in the 3′-UTR of certain mRNAs, affecting the translation of myelination-involved proteins. RNA binding has been earlier structurally characterized, but information about full-length QKI6 conformation is lacking. Based on known domains and structure predicitons, we expected full-length QKI6 to be flexible and carry disordered regions. Hence, we carried out biophysical and structural characterization of human QKI6. Results We expressed and purified full-length QKI6 and characterized it using mass spectrometry, light scattering, small-angle X-ray scattering, and circular dichroism spectroscopy. QKI6 was monodisperse, folded, and mostly dimeric, being oxidation-sensitive. The C-terminal tail was intrinsically disordered, as predicted. In the absence of RNA, the RNA-binding subdomain is likely to present major flexibility. In thermal stability assays, a double sequential unfolding behaviour was observed in the presence of phosphate, which may interact with the RNA-binding domain. The results confirm the flexibility and partial disorder of QKI6, which may be functionally relevant.

Solution X-ray scattering study of a full-length class A penicillin-binding protein

2011 ◽  
Vol 405 (1) ◽  
pp. 107-111 ◽  
Author(s):  
P. Macheboeuf ◽  
M. Piuzzi ◽  
S. Finet ◽  
F. Bontems ◽  
J. Pérez ◽  
...  
Keyword(s):  
Binding Protein ◽  
Full Length ◽  
Length Class ◽  
Penicillin Binding Protein ◽  
X Ray ◽  
Class A ◽  
X Ray Scattering ◽  
Scattering Study ◽  
Ray Scattering

scholarly journals The disease associated Tau35 fragment has an increased propensity to aggregate compared to full-length tau

2021 ◽  
Author(s):  
Chen Lyu ◽  
Stefano Da Vela ◽  
Youssra K Al-Hilaly ◽  
Karen Marshall ◽  
Richard Thorogate ◽  
...  
Keyword(s):  
Progressive Increase ◽  
Full Length ◽  
Motor Dysfunction ◽  
Truncated Form ◽  
X Ray ◽  
Force Microscopy ◽  
X Ray Scattering ◽  
Atomic Force ◽  
Transmission Electron

Tau35 is a truncated form of tau found in human brain in a subset of tauopathies. Tau35 expression in mice recapitulates key features of human disease, including progressive increase in tau phosphorylation, along with cognitive and motor dysfunction. The appearance of aggregated tau suggests that Tau35 may have structural properties distinct from those of other tau species that could account for its pathological role in disease. To address this hypothesis, we performed a structural characterization of monomeric and aggregated Tau35 and compared the results to those of two longer isoforms, 2N3R and 2N4R tau. We used small angle X-ray scattering to show that Tau35, 2N3R and 2N4R tau all behave as disordered monomeric species but Tau35 exhibits higher rigidity. In the presence of the poly-anion heparin, Tau35 increases thioflavin T fluorescence significantly faster and to a greater extent than full-length tau, demonstrating a higher propensity to aggregate. We used atomic force microscopy, transmission electron microscopy and X-ray fiber diffraction to demonstrate that Tau35 aggregates are morphologically similar to previously reported tau fibrils but they are more densely packed. These data increase our understanding of the aggregation inducing properties of clinically relevant tau fragments and their potentially damaging role in the pathogenesis of human tauopathies.

scholarly journals Light-induced structural changes in a full-length cyanobacterial phytochrome probed by time-resolved X-ray scattering

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
Derren J. Heyes ◽  
Samantha J. O. Hardman ◽  
Martin N. Pedersen ◽  
Joyce Woodhouse ◽  
Eugenio De La Mora ◽  
...  
Keyword(s):  
Structural Changes ◽  
Full Length ◽  
Time Resolved ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

scholarly journals Crystallization and preliminary X-ray analysis of two variants of theEscherichia coliO157 ParE2–PaaA2 toxin–antitoxin complex

2014 ◽  
Vol 70 (9) ◽  
pp. 1284-1291 ◽  
Author(s):  
Yann G. J. Sterckx ◽  
Sarah Haesaerts ◽  
Laurence Van Melderen ◽  
Remy Loris
Keyword(s):  
Gel Filtration ◽  
Unit Cell ◽  
Full Length ◽  
Unit Cell Parameters ◽  
Space Group ◽  
X Ray ◽  
Cell Parameters ◽  
X Ray Scattering ◽  
Complex Forms

ThepaaR2–paaA2–parE2operon is a three-component toxin–antitoxin module encoded in the genome of the human pathogenEscherichia coliO157. The toxin (ParE2) and antitoxin (PaaA2) interact to form a nontoxic toxin–antitoxin complex. In this paper, the crystallization and preliminary characterization of two variants of the ParE2–PaaA2 toxin–antitoxin complex are described. Selenomethionine-derivative crystals of the full-length ParE2–PaaA2 toxin–antitoxin complex diffracted to 2.8 Å resolution and belonged to space groupP41212 (orP43212), with unit-cell parametersa=b= 90.5,c= 412.3 Å. It was previously reported that the full-length ParE2–PaaA2 toxin–antitoxin complex forms a higher-order oligomer. In contrast, ParE2 and PaaA213–63, a truncated form of PaaA2 in which the first 12 N-terminal residues of the antitoxin have been deleted, form a heterodimer as shown by analytical gel filtration, dynamic light scattering and small-angle X-ray scattering. Crystals of the PaaA213–63–ParE2 complex diffracted to 2.7 Å resolution and belonged to space groupP6122 (orP6522), with unit-cell parametersa=b= 91.6,c= 185.6 Å.

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