scholarly journals Reversible supramolecular assembly of the anti-microbial peptide plectasin into helical non-amyloid fibrils

2021 ◽  
Author(s):  
Christin Pohl ◽  
Gregory Effantin ◽  
Eaazhisai Kandiah ◽  
Sebastian Meier ◽  
Guanghong Zeng ◽  
...  
Keyword(s):  
Self Assembly ◽  
Amyloid Fibrils ◽  
Supramolecular Assembly ◽  
Alpha Helix ◽  
Fibril Formation ◽  
Triple Mutant ◽  
Left Handed ◽  
High Resolution Structure ◽  
Sigmoidal Kinetics ◽  
Protein Fibril

Self-assembly and fibril formation play important roles in protein behavior. Amyloid fibrils formation is well-studied due to its role in neurodegenerative diseases and characterized by refolding of the protein into predominant β-sheet form. However, much less is known about the assembly of proteins into other types of supramolecular structures. Using cryo-electron microscopy at a resolution of 1.97 Angstroem, we show that a triple-mutant of the anti-microbial peptide plectasin assembles reversibly into helical non-amyloid fibrils. Plectasin contains a cysteine-stabilized alpha-helix/beta-sheets structure, which remains intact upon fibril formation. Two fibrils form a right-handed superstructure with each fibril consisting of double helical, left-handed structures. The fibril formation is reversible and follows sigmoidal kinetics with a pH-dependent equilibrium between soluble monomer and protein fibril. The anti-microbial activity does not appear compromised by fibril formation. This is the first high-resolution structure of this type of alpha/beta protein fibrils.

scholarly journals Modulation of Amyloidogenic Protein Self-Assembly Using Tethered Small Molecules

2020 ◽  
Author(s):  
Emma Cawood ◽  
Nicolas Guthertz ◽  
Jessica Ebo ◽  
Theodoros Karamanos ◽  
Sheena E. Radford FRS ◽  
...  
Keyword(s):  
Protein Interactions ◽  
Structural Characterization ◽  
Self Assembly ◽  
Molecular Mechanisms ◽  
Amyloid Fibrils ◽  
Fibril Formation ◽  
X Ray Crystallography ◽  
Starting Point ◽  
Amyloid Assembly

<p></p><p>Protein-protein interactions (PPIs) are involved in many of life’s essential biological functions yet are also an underlying cause of several human diseases, including amyloidosis. The modulation of PPIs presents opportunities to gain mechanistic insights into amyloid assembly, particularly through the use of methods which can trap specific intermediates for detailed study. Such information can also provide a starting point for drug discovery. Here, we demonstrate that covalently tethered small molecule fragments can be used to stabilize specific oligomers during amyloid fibril formation, facilitating the structural characterization of these assembly intermediates. We exemplify the power of covalent tethering using the naturally occurring truncated variant (ΔN6) of the human protein β2-microglobulin (β2m), which assembles into amyloid fibrils associated with dialysis-related amyloidosis. Using this approach, we have trapped tetramers formed by ΔN6 under conditions which would normally lead to fibril formation and found that the degree of tetramer stabilization depends on the site of the covalent tether and the nature of the protein-fragment interaction. The covalent protein-ligand linkage enabled structural characterization of these trapped oligomeric species using X-ray crystallography and NMR, providing insight into why tetramer stabilization inhibits amyloid assembly. Our findings highlight the power of “post-translational chemical modification" as a tool to study biological molecular mechanisms. </p><br><p></p>

Role of Anion–π Interactions in the Supramolecular Assembly of Salts Containing Asymmetrical Bis(pyridyl) Cations

2014 ◽  
Vol 67 (10) ◽  
pp. 1504
Author(s):  
Zhu-Yan Zhang ◽  
Zhao-Peng Deng ◽  
Li-Hua Huo ◽  
Shu-E Zhang ◽  
Hui Zhao ◽  
...  
Keyword(s):  
Hydrogen Bonds ◽  
Self Assembly ◽  
Supramolecular Assembly ◽  
Interpenetrating Networks ◽  
Π Interactions ◽  
Supramolecular Architectures ◽  
Left Handed ◽  
Inorganic Acids ◽  
Thermal Stability Of

Self-assembly of three flexible bis(pyridyl) molecules with different inorganic acids (HPF6, HClO4, and HNO3) leads to the formation of eight salts, which exhibit diverse architectures involving hydrogen bonding and anion–π interactions. The three types of inorganic anions in these salts formed anion–π interactions with HM+ and H2M2+ except for 2, in which the six F atoms were involved in hydrogen bonds. Anion–π interactions produced diverse motifs of one (anion)-to-one (cation) in 1, 3, 4, and 6, two (anion)-to-one (cation) in 5 and 7, and (4,4) layer in 8. Hydrogen bonds resulted in interesting supramolecular architectures, such as right- and left-handed helical chains in 3, 2-fold interpenetrating networks in 5, and 3-fold interpenetrating networks in 8. Structural analyses indicated that the conformations of the three flexible asymmetrical bis(pyridyl) molecules and the non-covalent bonding interactions, such as hydrogen bonds and anion···π interactions, play crucial roles in the final architectures of these salts. Thermogravimetric analyses indicated that the thermal stability of the eight salts decreased in the order of perchlorates, hexafluorophosphates, and nitrates. The emission intensity of the perchlorates is much stronger than that of the hexafluorophosphates, nitrates, and their corresponding organic molecules in the solid state at room temperature.

scholarly journals Physical Determinants of Amyloid Assembly in Biofilm Formation

mBio ◽  
2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Maria Andreasen ◽  
Georg Meisl ◽  
Jonathan D. Taylor ◽  
Thomas C. T. Michaels ◽  
Aviad Levin ◽  
...  
Keyword(s):  
Extracellular Matrix ◽  
Self Assembly ◽  
Biofilm Formation ◽  
Amyloid Fibrils ◽  
Environmental Stresses ◽  
Fibril Formation ◽  
Functional Amyloid ◽  
Content Type ◽  
Wide Range ◽  
Amyloid Assembly

ABSTRACTA wide range of bacterial pathogens have been shown to form biofilms, which significantly increase their resistance to environmental stresses, such as antibiotics, and are thus of central importance in the context of bacterial diseases. One of the major structural components of these bacterial biofilms are amyloid fibrils, yet the mechanism of fibril assembly and its importance for biofilm formation are currently not fully understood. By studying fibril formationin vitro, in a model system of two common but unrelated biofilm-forming proteins, FapC fromPseudomonas fluorescensand CsgA fromEscherichia coli, we found that the two proteins have a common aggregation mechanism. In both systems, fibril formation proceeds via nucleated growth of linear fibrils exhibiting similar measured rates of elongation, with negligible fibril self-replication. These similarities between two unrelated systems suggest that convergent evolution plays a key role in tuning the assembly kinetics of functional amyloid fibrils and indicates that only a narrow window of mechanisms and assembly rates allows for successful biofilm formation. Thus, the amyloid assembly reaction is likely to represent a means for controlling biofilm formation, both by the organism and by possible inhibitory drugs.IMPORTANCEBiofilms are generated by bacteria, embedded in the formed extracellular matrix. The biofilm's function is to improve the survival of a bacterial colony through, for example, increased resistance to antibiotics or other environmental stresses. Proteins secreted by the bacteria act as a major structural component of this extracellular matrix, as they self-assemble into highly stable amyloid fibrils, making the biofilm very difficult to degrade by physical and chemical means once formed. By studying the self-assembly mechanism of the fibrils from their monomeric precursors in two unrelated bacteria, our experimental and theoretical approaches shed light on the mechanism of functional amyloid assembly in the context of biofilm formation. Our results suggest that fibril formation may be a rate-limiting step in biofilm formation, which in turn has implications on the protein self-assembly reaction as a target for potential antibiotic drugs.

New clues into the self-assembly of Vmh2, a basidiomycota class I hydrophobin

2018 ◽  
Vol 399 (8) ◽  
pp. 895-901 ◽  
Author(s):  
Anna Pennacchio ◽  
Paola Cicatiello ◽  
Eugenio Notomista ◽  
Paola Giardina ◽  
Alessandra Piscitelli
Keyword(s):  
Self Assembly ◽  
Amyloid Fibrils ◽  
Amyloid Fibril ◽  
Fibril Formation ◽  
The Self ◽  
Class I ◽  
Molecular Determinants

Abstract Hydrophobins are fungal proteins that can self-assemble into amphiphilic films at hydrophobic-hydrophilic interfaces. Class I hydrophobin aggregates resemble amyloid fibrils, sharing some features with them. Here, five site-directed mutants of Vmh2, a member of basidiomycota class I hydrophobins, were designed and characterized to elucidate the molecular determinants playing a key role in class I hydrophobin self-assembly. The mechanism of fibril formation proposed for Vmh2 foresees that the triggering event is the destabilization of a specific loop (L1), leading to the formation of a β-hairpin, which in turn generates the β-spine of the amyloid fibril.

scholarly journals Modulation of Amyloidogenic Protein Self-Assembly Using Tethered Small Molecules

2020 ◽  
Author(s):  
Emma Cawood ◽  
Nicolas Guthertz ◽  
Jessica Ebo ◽  
Theodoros Karamanos ◽  
Sheena E. Radford FRS ◽  
...  
Keyword(s):  
Protein Interactions ◽  
Structural Characterization ◽  
Self Assembly ◽  
Molecular Mechanisms ◽  
Amyloid Fibrils ◽  
Fibril Formation ◽  
X Ray Crystallography ◽  
Starting Point ◽  
Amyloid Assembly

<p></p><p>Protein-protein interactions (PPIs) are involved in many of life’s essential biological functions yet are also an underlying cause of several human diseases, including amyloidosis. The modulation of PPIs presents opportunities to gain mechanistic insights into amyloid assembly, particularly through the use of methods which can trap specific intermediates for detailed study. Such information can also provide a starting point for drug discovery. Here, we demonstrate that covalently tethered small molecule fragments can be used to stabilize specific oligomers during amyloid fibril formation, facilitating the structural characterization of these assembly intermediates. We exemplify the power of covalent tethering using the naturally occurring truncated variant (ΔN6) of the human protein β2-microglobulin (β2m), which assembles into amyloid fibrils associated with dialysis-related amyloidosis. Using this approach, we have trapped tetramers formed by ΔN6 under conditions which would normally lead to fibril formation and found that the degree of tetramer stabilization depends on the site of the covalent tether and the nature of the protein-fragment interaction. The covalent protein-ligand linkage enabled structural characterization of these trapped oligomeric species using X-ray crystallography and NMR, providing insight into why tetramer stabilization inhibits amyloid assembly. Our findings highlight the power of “post-translational chemical modification" as a tool to study biological molecular mechanisms. </p><br><p></p>

scholarly journals Pancreatic beta-cell granule peptides form heteromolecular complexes which inhibit islet amyloid polypeptide fibril formation

2004 ◽  
Vol 377 (3) ◽  
pp. 709-716 ◽  
Author(s):  
Emma T. A. S. JAIKARAN ◽  
Melanie R. NILSSON ◽  
Anne CLARK
Keyword(s):  
Type 2 Diabetes ◽  
Amyloid Fibrils ◽  
Secretory Granules ◽  
Pancreatic Beta Cell ◽  
Islet Amyloid Polypeptide ◽  
Fibril Formation ◽  
Islet Amyloid ◽  
Β Sheet

Islet amyloid polypeptide (IAPP), or ‘amylin’, is co-stored with insulin in secretory granules of pancreatic islet β-cells. In Type 2 diabetes, IAPP converts into a β-sheet conformation and oligomerizes to form amyloid fibrils and islet deposits. Granule components, including insulin, inhibit spontaneous IAPP fibril formation in vitro. To determine the mechanism of this inhibition, molecular interactions of insulin with human IAPP (hIAPP), rat IAPP (rIAPP) and other peptides were examined using surface plasmon resonance (BIAcore), CD and transmission electron microscopy (EM). hIAPP and rIAPP complexed with insulin, and this reaction was concentration-dependent. rIAPP and insulin, but not pro-insulin, bound to hIAPP. Insulin with a truncated B-chain, to prevent dimerization, also bound hIAPP. In the presence of insulin, hIAPP did not spontaneously develop β-sheet secondary structure or form fibrils. Insulin interacted with pre-formed IAPP fibrils in a regular repeating pattern, as demonstrated by immunoEM, suggesting that the binding sites for insulin remain exposed in hIAPP fibrils. Since rIAPP and hIAPP form complexes with insulin (and each other), this could explain the lack of amyloid fibrils in transgenic mice expressing hIAPP. It is likely that IAPP fibrillogenesis is inhibited in secretory granules (where the hIAPP concentration is in the millimolar range) by heteromolecular complex formation with insulin. Alterations in the proportions of insulin and IAPP in granules could disrupt the stability of the peptide. The increase in the proportion of unprocessed pro-insulin produced in Type 2 diabetes could be a major factor in destabilization of hIAPP and induction of fibril formation.

Morphology engineering: dramatic roles of serine and threonine in supramolecular assembly

RSC Advances ◽  
2016 ◽  
Vol 6 (48) ◽  
pp. 41761-41764 ◽  
Author(s):  
M. B. Bijesh ◽  
Rituraj Mishra ◽  
Narayanan D. Kurur ◽  
V. Haridas
Keyword(s):  
Self Assembly ◽  
Supramolecular Assembly ◽  
Morphology Engineering ◽  
Self Assembled

Macrocycles containing serine self-assembled into fibres, while threonine induced vesicular self-assembly. Macrocycles with serine can be driven to form vesicular assembly by incorporating a non-planar spacer.

scholarly journals Observation of an α-synuclein liquid droplet state and its maturation into Lewy body-like assemblies

2021 ◽  
Author(s):  
Maarten C Hardenberg ◽  
Tessa Sinnige ◽  
Sam Casford ◽  
Samuel Dada ◽  
Chetan Poudel ◽  
...  
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Self Assembly ◽  
Lewy Body ◽  
Amyloid Fibrils ◽  
Liquid Droplet ◽  
Large Body ◽  
Lewy Bodies ◽  
Cellular Components

Abstract Misfolded α-synuclein is a major component of Lewy bodies, which are a hallmark of Parkinson’s disease. A large body of evidence shows that α-synuclein can aggregate into amyloid fibrils, but the relationship between α-synuclein self-assembly and Lewy body formation remains unclear. Here we show, both in vitro and in a Caenorhabditis elegans model of Parkinson’s disease, that α-synuclein undergoes liquid‒liquid phase separation by forming a liquid droplet state, which converts into an amyloid-rich hydrogel with Lewy-body-like properties. This maturation process towards the amyloid state is delayed in the presence of model synaptic vesicles in vitro. Taken together, these results suggest that the formation of Lewy bodies may be linked to the arrested maturation of α-synuclein condensates in the presence of lipids and other cellular components.

Examining the structure of the mature amyloid fibril

2002 ◽  
Vol 30 (4) ◽  
pp. 521-525 ◽  
Author(s):  
O. S. Makin ◽  
L. C. Serpell
Keyword(s):  
Self Assembly ◽  
Rational Design ◽  
Amyloid Fibrils ◽  
Structural Information ◽  
X Ray ◽  
X Ray Crystallography ◽  
Cryo Electron Microscopy ◽  
Fibre Diffraction ◽  
Complementary Techniques ◽  
Mature Fibril

The pathogenesis of the group of diseases known collectively as the amyloidoses is characterized by the deposition of insoluble amyloid fibrils. These are straight, unbranching structures about 70–120 å (1 å = 0.1 nm) in diameter and of indeterminate length formed by the self-assembly of a diverse group of normally soluble proteins. Knowledge of the structure of these fibrils is necessary for the understanding of their abnormal assembly and deposition, possibly leading to the rational design of therapeutic agents for their prevention or disaggregation. Structural elucidation is impeded by fibril insolubility and inability to crystallize, thus preventing the use of X-ray crystallography and solution NMR. CD, Fourier-transform infrared spectroscopy and light scattering have been used in the study of the mechanism of fibril formation. This review concentrates on the structural information about the final, mature fibril and in particular the complementary techniques of cryo-electron microscopy, solid-state NMR and X-ray fibre diffraction.

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