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1.
Protein aggregation is a process in which proteins self-associate into imperfectly ordered macroscopic entities. Such aggregates are generally classified as either amorphous or highly ordered, the most common form of the latter being amyloid fibrils. Amyloid fibrils composed of cross-β-sheet structure are the pathological hallmarks of several diseases including Alzheimer’s disease, but are also associated with functional states such as the fungal HET-s prion. This review aims to summarize the recent high-resolution structural studies of amyloid fibrils in light of their (potential) activities. We propose that the repetitive nature of the cross-β-sheet structure of amyloids is key for their multiple properties: the repeating motifs can translate a rather non-specific interaction into a specific one through cooperativity. 相似文献
2.
Natallia Makarava Valeriy G. Ostapchenko Regina Savtchenko Ilia V. Baskakov 《The Journal of biological chemistry》2009,284(21):14386-14395
A key structural component of amyloid fibrils is a highly ordered,
crystalline-like cross-β-sheet core. Conformationally different amyloid
structures can be formed within the same amino acid sequence. It is generally
assumed that individual fibrils consist of conformationally uniform
cross-β-structures. Using mammalian recombinant prion protein (PrP), we
showed that, contrary to common perception, amyloid is capable of
accommodating a significant conformational switching within individual
fibrils. The conformational switch occurred when the amino acid sequence of a
PrP variant used as a precursor substrate in a fibrillation reaction was not
compatible with the strain-specific conformation of the fibrillar template.
Despite the mismatch in amino acid sequences between the substrate and
template, individual fibrils recruited the heterologous PrP variant; however,
the fibril elongation proceeded through a conformational adaptation, resulting
in a change in amyloid strain within individual fibrils. This study
illustrates the high adaptation potential of amyloid structures and suggests
that conformational switching within individual fibrils may account for
adaptation of amyloid strains to a heterologous substrate. This work proposes
a new mechanistic explanation for the phenomenon of strain conversion and
illustrates the direction in evolution of amyloid structures. This study also
provides a direct illustration that catalytic activity of self-replicating
amyloid structures is not ultimately coupled with their templating effect.The ability to form amyloid structures is considered to be one of the most
general properties of a polypeptide backbone
(1). Regardless of the specific
peptides or proteins involved in fibril formation, all types of amyloid
fibrils share a common structural motif that consists of a
cross-β-structure (2).
Cross-β-structures are comprised of highly ordered, nearly anhydrous,
crystalline-like β-sheets stabilized by hydrogen bonding and densely
packed side chains (3,
4). Growing evidence indicates
that multiple amyloid structures referred to as amyloid strains could be
formed within the same amino acid sequence
(5–7).Amyloids are capable of self-replicating
(8). Self-replicating
properties of amyloid fibrils are attributed to the unique arrangement of
cross-β-strands that are assembled perpendicular to the fibrillar axis,
where β-strands at the growing edge provide a template for recruiting and
converting a monomeric precursor. The self-replicating property of the amyloid
cross-β-structure consists of two activities: catalytic (i.e.
the ability to convert a monomeric precursor into an amyloid state) and
templating (i.e. the ability to accurately imprint the
strain-specific conformation onto a newly recruited polypeptide). The
templating activity is believed to be intimately coupled to the catalytic
activity and accounts for the high fidelity of amyloid replication. High
fidelity of replication requires identity or high homology between the amino
acid sequences of a fibrillar template and a precursor substrate. The species
specificity of a template-substrate interaction is believed to account for the
species barrier in prion transmission and species specificity of in
vitro cross-seeded fibrillation reactions. Local perturbations arising
due to mismatches in packing of amino acid side chains within the
crystalline-like cross-β-structures could prevent efficient replication
of amyloid fibrils.It is generally assumed that individual fibrils are structurally uniform,
i.e. maintain the same structure of a cross-β-core throughout
the fibrillar length. In the current study, we showed that, contrary to the
common perception, amyloid fibrils are capable of accommodating significant
conformational switching within individual fibrils. The conformational switch
occurred when the amino acid sequence of the precursor substrate was not
compatible with the conformation of the template. Despite mismatched amino
acid sequences, individual fibrils were able to recruit the heterologous
recombinant prion protein
(PrP)2 variant;
however, fibril elongation proceeded through switching to a new conformational
state. The implications of these studies are multifold. First, our work
illustrates the high adaptation potential of amyloid structures and suggests
that the conformational switch accounts for adaptation of amyloid strains to
the heterologous substrate. Second, the current studies propose a new
molecular explanation for the phenomenon referred to as convergence of
strains. Third, this work illustrates the directionality in evolution of
amyloid structures, showing that the species-specific amyloid structures
(i.e. structures that exist only within a single PrP sequence) can
give rise to promiscuous or indiscriminative structures (structures compatible
with several PrP variants), but not vice versa. Finally, our studies provide
direct illustration that catalytic activity of self-replicating amyloid
structures is not ultimately coupled with their templating effect. 相似文献
3.
Peleg Ragonis-Bachar Gabriel Axel Shahar Blau Nir Ben-Tal Rachel Kolodny Meytal Landau 《Proteins》2024,92(2):265-281
Amyloids, protein, and peptide assemblies in various organisms are crucial in physiological and pathological processes. Their intricate structures, however, present significant challenges, limiting our understanding of their functions, regulatory mechanisms, and potential applications in biomedicine and technology. This study evaluated the AlphaFold2 ColabFold method's structure predictions for antimicrobial amyloids, using eight antimicrobial peptides (AMPs), including those with experimentally determined structures and AMPs known for their distinct amyloidogenic morphological features. Additionally, two well-known human amyloids, amyloid-β and islet amyloid polypeptide, were included in the analysis due to their disease relevance, short sequences, and antimicrobial properties. Amyloids typically exhibit tightly mated β-strand sheets forming a cross-β configuration. However, certain amphipathic α-helical subunits can also form amyloid fibrils adopting a cross-α structure. Some AMPs in the study exhibited a combination of cross-α and cross-β amyloid fibrils, adding complexity to structure prediction. The results showed that the AlphaFold2 ColabFold models favored α-helical structures in the tested amyloids, successfully predicting the presence of α-helical mated sheets and a hydrophobic core resembling the cross-α configuration. This implies that the AI-based algorithms prefer assemblies of the monomeric state, which was frequently predicted as helical, or capture an α-helical membrane-active form of toxic peptides, which is triggered upon interaction with lipid membranes. 相似文献
4.
Fibril conformation as the basis of species- and strain-dependent seeding specificity of mammalian prion amyloids 总被引:7,自引:0,他引:7
Spongiform encephalopathies are believed to be transmitted by self-perpetuating conformational conversion of the prion protein. It was shown recently that fundamental aspects of mammalian prion propagation can be reproduced in vitro in a seeded fibrillization of the recombinant prion protein variant Y145Stop (PrP23-144). Here we demonstrate that PrP23-144 amyloids from different species adopt distinct secondary structures and morphologies, and that these structural differences are controlled by one or two residues in a critical region. These sequence-specific structural characteristics correlate strictly with the seeding specificity of amyloid fibrils. However, cross-seeding of PrP23-144 from one species with preformed fibrils from another species may overcome natural sequence-based structural preferences, resulting in a new amyloid strain that inherits the secondary structure and morphology of the template. These data provide direct biophysical evidence that protein conformations are transmitted in PrP amyloid strains, establishing a foundation for a structural basis of mammalian prion transmission barriers. 相似文献
5.
Ilia V Baskakov 《朊病毒》2014,8(2):169-172
In several recent studies transmissible prion disease was induced in animals by inoculation with recombinant prion protein amyloid fibrils produced in vitro. Serial transmission of amyloid fibrils gave rise to a new class of prion strains of synthetic origin. Gradual transformation of disease phenotypes and PrPSc properties was observed during serial transmission of synthetic prions, a process that resembled the phenomenon of prion strain adaptation. The current article discusses the remarkable parallels between phenomena of prion strain adaptation that accompanies cross-species transmission and the evolution of synthetic prions occurring within the same host. Two alternative mechanisms underlying prion strain adaptation and synthetic strain evolution are discussed. The current article highlights the complexity of the prion transmission barrier and strain adaptation and proposes that the phenomenon of prion adaptation is more common than previously thought. 相似文献
6.
Mantas Malisauskas Kiran Yanamandra Ludmilla Morozova-Roche 《Journal of molecular biology》2010,396(1):60-74
Amyloid formation is a universal behavior of proteins central to many important human pathologies and industrial processes. The extreme stability of amyloids towards chemical and proteolytic degradation is an acquired property compared to the precursor proteins and is a major prerequisite for their accumulation. Here, we report a study on the lability of human insulin amyloid as a function of pH and amyloid ageing. Using a range of methods such as atomic force microscopy, thioflavin T fluorescence, circular dichroism, and gas-phase electrophoretic mobility macromolecule analysis, we probed the propensity of human insulin amyloid to propagate or dissociate in a wide span of pH values and ageing in a low concentration regime. We generated a three-dimensional amyloid lability landscape in coordinates of pH and amyloid ageing, which displays three distinctive features: (i) a maximum propensity to grow near pH 3.8 and an age corresponding to the inflection point of the growth phase, (ii) an abrupt cutoff between growth and disaggregation at pH 8-10, and (iii) isoclines shifted towards older age during the amyloid growth phase at pH 4-9, reflecting the greater stability of aged amyloid. Thus, lability of amyloid strongly depends on the ionization state of insulin and on the structure and maturity of amyloid fibrils. The stability of insulin amyloid towards protease K was assessed by using real-time atomic force microscopy and thioflavin T fluorescence. We estimated that amyloid fibrils can be digested both from the free ends and within the length of the fibril with a rate of ca 4 nm/min. Our results highlight that amyloid structures, depending on solution conditions, can be less stable than commonly perceived. These results have wide implications for understanding the propagation of amyloids via a seeding mechanism as well as for understanding their natural clearance and dissociation under solution conditions unfavorable for amyloid formation in biological systems and industrial applications. 相似文献
7.
Irina Randrianjatovo-Gbalou Claire-Emmanuelle Marcato-RomainElisabeth Girbal-Neuhauser 《Analytical biochemistry》2015
An amyloid fibrils investigation within biofilm samples requires distinguishing the amyloid β-sheet structure of these proteins and quantifying them. In this study, the property of amyloids to incorporate the fluorescent dye Thioflavin T has been exploited to propose a method of quantification. The experimental protocol includes the preparation of amyloids from commercial κ-casein (κCN) and their fractionation through size exclusion chromatography (SEC) to provide calibration curves from fluorescence and absorbance signals. Finally, a bacterial biofilm extract was injected into SEC, and the amyloid fibrils could be expressed as equivalent κCN, representing approximately 21% of the total proteins. 相似文献
8.
《Journal of molecular biology》2023,435(18):168215
Immunoglobulin light chain amyloidosis (AL) is caused by the aberrant production of amyloidogenic light chains (LC) that accumulate as amyloid deposits in vital organs. Distinct LC sequences in each patient yield distinct amyloid structures. However different tissue microenvironments may also cause identical protein precursors to adopt distinct amyloid structures. To address the impact of the tissue environment on the structural polymorphism of amyloids, we extracted fibrils from the kidney of an AL patient (AL55) whose cardiac amyloid structure was previously determined by our group. Here we show that the 4.0 Å resolution cryo-EM structure of the renal fibril is virtually identical to that reported for the cardiac fibril. These results provide the first structural evidence that LC amyloids independently deposited in different organs of the same AL patient share a common fold. 相似文献
9.
Protein aggregation and amyloid formation are associated with both pathological conditions in humans such as Alzheimer's disease and native functions such as peptide hormone storage in the pituitary secretory granules in mammals. Here, we studied amyloid fibrils formation by three neuropeptides namely physalaemin, kassinin and substance P of tachykinin family using biophysical techniques including circular dichroism, thioflavin T, congo red binding and microscopy. All these neuropeptides under study have significant sequence similarity with Aβ(25-35) that is known to form neurotoxic amyloids. We found that all these peptides formed amyloid-like fibrils in vitro in the presence of heparin, and these amyloids were found to be nontoxic in neuronal cells. However, the extent of amyloid formation, structural transition, and morphology were different depending on the primary sequences of peptide. When Aβ(25-35) and Aβ40 were incubated with each of these neuropeptides in 1:1 ratio, a drastic increase in amyloid growths were observed compared to that of individual peptides suggesting that co-aggregation of Aβ and these neuropeptides. The electron micrographs of these co-aggregates were dissimilar when compared with individual peptide fibrils further supporting the possible incorporation of these neuropeptides in Aβ amyloid fibrils. Further, the fibrils of these neuropeptides can seed the fibrils formation of Aβ40 and reduced the toxicity of preformed Aβ fibrils. The present study of amyloid formation by tachykinin neuropeptides is not only providing an understanding of the mechanism of amyloid fibril formation in general, but also offering plausible explanation that why these neuropeptide might reduce the cytotoxicity associated with Alzheimer's disease related amyloids. 相似文献
10.
Amyloid accomplices and enforcers 总被引:3,自引:0,他引:3
Amyloid-related diseases are often ascribed to protein "misfolding." Yet in the absence of high-resolution structures for mature fibrils or intermediates, the connection between the mechanism of amyloid formation and protein folding remains tenuous. The simplistic view of amyloid fibrillogenesis as a homogeneous self-assembly process is being increasingly challenged by observations that amyloids interact with a variety of cofactors including metals, glycosaminoglycans, glycoproteins such as serum amyloid P and apolipo-protein E, and constituents of basement membranes such as perlecan, laminin, and agrin. These "pathological chaperones" have effects that range from mediating the rate of amyloid fibril formation to increasing the stability of amyloid deposits, and may contribute to amyloid toxicity. An increasing appreciation of the role of accessory molecules in amyloid etiology has paved the way to novel diagnostics and therapeutic strategies. 相似文献
11.
Amyloid fibrils are associated with many maladies, including Alzheimer’s disease (AD). The isolation of amyloids from natural materials is very challenging because the extreme structural stability of amyloid fibrils makes it difficult to apply conventional protein science protocols to their purification. A protocol to isolate and detect amyloids is desired for the diagnosis of amyloid diseases and for the identification of new functional amyloids. Our aim was to develop a protocol to purify amyloid from organisms, based on the particular characteristics of the amyloid fold, such as its resistance to proteolysis and its capacity to be recognized by specific conformational antibodies. We used a two-step strategy with proteolytic digestion as the first step followed by immunoprecipitation using the amyloid conformational antibody LOC. We tested the efficacy of this method using as models amyloid fibrils produced in vitro, tissue extracts from C. elegans that overexpress Aβ peptide, and cerebrospinal fluid (CSF) from patients diagnosed with AD. We were able to immunoprecipitate Aβ1–40 amyloid fibrils, produced in vitro and then added to complex biological extracts, but not α-synuclein and gelsolin fibrils. This method was useful for isolating amyloid fibrils from tissue homogenates from a C. elegans AD model, especially from aged worms. Although we were able to capture picogram quantities of Aβ1–40 amyloid fibrils produced in vitro when added to complex biological solutions, we could not detect any Aβ amyloid aggregates in CSF from AD patients. Our results show that although immunoprecipitation using the LOC antibody is useful for isolating Aβ1–40 amyloid fibrils, it fails to capture fibrils of other amyloidogenic proteins, such as α-synuclein and gelsolin. Additional research might be needed to improve the affinity of these amyloid conformational antibodies for an array of amyloid fibrils without compromising their selectivity before application of this protocol to the isolation of amyloids. 相似文献
12.
Bayro MJ Daviso E Belenky M Griffin RG Herzfeld J 《The Journal of biological chemistry》2012,287(5):3479-3484
Functional amyloids have been identified in a wide range of organisms, taking on a variety of biological roles and being controlled by remarkable mechanisms of directed assembly. Here, we report that amyloid fibrils constitute the ribs of the buoyancy organelles of Anabaena flos-aquae. The walls of these gas-filled vesicles are known to comprise a single protein, GvpA, arranged in a low pitch helix. However, the tertiary and quaternary structures have been elusive. Using solid-state NMR correlation spectroscopy we find detailed evidence for an extended cross-β structure. This amyloid assembly helps to account for the strength and amphiphilic properties of the vesicle wall. Buoyancy organelles thus dramatically extend the scope of known functional amyloids. 相似文献
13.
In addition to being associated with severe degenerative diseases, amyloids show exceptional mechanical properties including great strength, sturdiness and elasticity. However, thus far physical models that explain these properties remain elusive, and our understanding of molecular deformation and failure mechanisms of individual amyloid fibrils is limited. Here we report a series of molecular dynamics simulations, carried out to analyze the mechanical response of two-fold symmetric Aβ(1–40) amyloid fibrils, twisted protein nanofilaments consisting of a H-bonded layered structure. We find a correlation of the mechanical behavior with chemical and nanostructural rearrangements of the fibril during compressive and tensile deformation, showing that the density of H-bonds varies linearly with the measured strain. Further, we find that both compressive and tensile deformation is coupled with torsional deformation, which is manifested in a strong variation of the interlayer twist angle that is found to be proportional to both the applied stress and measured strain. In both compression and tension we observe an increase of the Young's modulus from 2.34 GPa (for less than 0.1% strain in compression and 0.2% strain in tension), to 12.43 GPa for compression and 18.05 GPa for tension. The moduli at larger deformation are in good agreement with experimental data, where values in the range of 10–20 GPa have been reported. Our studies confirm that amyloids feature a very high stiffness, and elucidate the importance of the chemical and structural rearrangements of the fibrils during deformation. 相似文献
14.
Nani Van Gerven Sander E. Van der Verren Dirk M. Reiter Han Remaut 《Journal of molecular biology》2018,430(20):3657-3684
Amyloid fibrils are best known as a product of human and animal protein misfolding disorders, where amyloid formation is associated with cytotoxicity and disease. It is now evident that for some proteins, the amyloid state constitutes the native structure and serves a functional role. These functional amyloids are proving widespread in bacteria and fungi, fulfilling diverse functions as structural components in biofilms or spore coats, as toxins and surface-active fibers, as epigenetic material, peptide reservoirs or adhesins mediating binding to and internalization into host cells. In this review, we will focus on the role of functional amyloids in bacterial pathogenesis. The role of functional amyloids as virulence factor is diverse but mostly indirect. Nevertheless, functional amyloid pathways deserve consideration for the acute and long-term effects of the infectious disease process and may form valid antimicrobial targets. 相似文献
15.
Frank Shewmaker Ryan P. McGlinchey Kent R. Thurber Peter McPhie Fred Dyda Robert Tycko Reed B. Wickner 《The Journal of biological chemistry》2009,284(37):25065-25076
The extracellular curli proteins of Enterobacteriaceae form fibrous structures that are involved in biofilm formation and adhesion to host cells. These curli fibrils are considered a functional amyloid because they are not a consequence of misfolding, but they have many of the properties of protein amyloid. We confirm that fibrils formed by CsgA and CsgB, the primary curli proteins of Escherichia coli, possess many of the hallmarks typical of amyloid. Moreover we demonstrate that curli fibrils possess the cross-β structure that distinguishes protein amyloid. However, solid state NMR experiments indicate that curli structure is not based on an in-register parallel β-sheet architecture, which is common to many human disease-associated amyloids and the yeast prion amyloids. Solid state NMR and electron microscopy data are consistent with a β-helix-like structure but are not sufficient to establish such a structure definitively.Interest in amyloid is largely because of its association with many late onset human diseases, including Alzheimer disease (Aβ),2 Parkinson disease (α-synuclein), type II diabetes (amylin), and the transmissible spongiform encephalopathies (PrP). In each case a particular endogenous protein becomes incorporated into large aggregates known as amyloid, which was originally defined by pathologists as a tissue deposit staining like starch (1). However, the term amyloid has come to mean a filamentous protein aggregate with cross-β secondary structure (cross-β means that the β-strands that form β-sheets in the amyloid fibrils run approximately perpendicular to the long axis of the fibril with interstrand hydrogen bonds that run approximately parallel to the long axis) and protease resistance. Morphologically amyloid fibrils may vary in length from tens of nanometers to micrometers and have diameters in the range of 3–10 nm, although lateral association can produce much larger apparent diameters.Proteins from a variety of organisms can form amyloid both in vitro and in vivo, and the propensity to form amyloid may be a common property of many proteins (2). In addition to disease-associated amyloids, there are several confirmed cases of functional amyloid (for a review, see Ref. 3). For example, hydrophobins are amyloid-like proteins that coat the surface of fungal cells, and amyloid fibrils coating fish eggs protect them from dehydration (4, 5). The [Het-s] prion of Podospora anserina is involved in heterokaryon incompatibility, a recognition of non-self reaction believed to be important as a defense against fungal virus infection (6).Curli are extracellular filamentous structures of Enterobacteriaceae (7) that are integral to biofilm formation and are the major protein component of the extracellular matrix of these organisms (8). Curli of Escherichia coli are composed of the secreted proteins CsgA and CsgB. The latter is believed to prime the polymerization of the former and anchor the fibrils to the outer membrane (9). Both CsgA and CsgB fibrils are β-sheet-rich and, like amyloids, stain with the dye Congo red (10, 11).Because amyloid fibrils are non-crystalline and insoluble, solution NMR and x-ray crystallography are not directly applicable in structural studies. Solid state NMR and electron spin resonance have both been useful in obtaining constraints on amyloid structures and, in some cases, determining detailed structural information. The disease-associated amyloids formed by Aβ, amylin, α-synuclein, and tau along with the infectious amyloids of several yeast prions each have in-register parallel β-sheet structure (12–19).Here we confirm that the fibrils formed in vitro by CsgA and CsgB proteins are amyloids and explore their structure using solid state NMR and electron microscopy. Our results indicate that, unlike the pathogenic amyloids of humans and yeast, CsgA and CsgB amyloids are not in-register parallel β-sheet structures. Solid state NMR and electron microscopy data are consistent with a β-helix-like structure but do not establish such a structure definitively. 相似文献
16.
Zhang X Sun XX Xue D Liu DG Hu XY Zhao M Yang SG Yang Y Xia YJ Wang Y Liu RT 《Biochimica et biophysica acta》2011,1814(12):1703-1712
Increasing evidence indicates that amyloid aggregates, including oligomers, protofibrils or fibrils, are pivotal toxins in the pathogenesis of many amyloidoses such as Alzheimer's disease (AD), Parkinson's disease, Huntington's disease, prion-related diseases, type 2 diabetes and hereditary renal amyloidosis. Various oligomers assembled from different amyloid proteins share common structures and epitopes. Here we present data indicating that two oligomer-specific single chain variable fragment (scFv) antibodies isolated from a na?ve human scFv library could conformation-dependently recognize oligomers assembled from α-synuclein, amylin, insulin, Aβ1-40, prion peptide 106-126 and lysozyme, and fibrils from lysozyme. Further investigation showed that both scFvs inhibited the fibrillization of α-synuclein, amylin, insulin, Aβ1-40 and prion peptide 106-126, and disaggregated their preformed fibrils. However, they both promoted the aggregation of lysozyme. Nevertheless, the two scFv antibodies could attenuate the cytotoxicity of all amyloids tested. Moreover, the scFvs recognized the amyloid oligomers in all types of plaques, Lewy bodies and amylin deposits in the brain tissues of AD and PD patients and the pancreas of type 2 diabetes patients respectively, and showed that most amyloid fibril deposits were colocalized with oligomers in the tissues. Such conformation-dependent scFv antibodies may have potential application in the investigation of aggregate structures, the mechanisms of aggregation and cytotoxicity of various amyloids, and in the development of diagnostic and therapeutic reagents for many amyloidoses. 相似文献
17.
Tetsuyuki Kitamoto Kohtaro Hikita Takatoshi Tashima Jun Tateishi Yuji Sato 《Bioscience reports》1986,6(5):459-465
We identified fibrils from non-transmissible systemic and cerebral amyloidosis using the purification method of scrapie-associated fibrils (SAF). The fibrils possessed the same nature of congophilia, filamentous structures and molecular weights as amyloid fibrils, and were resistant to Proteinase K digestion. This SAF method makes for a rapid extraction from amyloid-laden tissues. The method, therefore, may purify nontransmissible amyloids alone or together with SAF proteins. 相似文献
18.
Marsagishvili LG Shpagina MD Shatalin IuV Shubina VS Naumov AA Potselueva MM Podlubnaia ZA 《Biofizika》2006,51(5):799-803
It is known that amyloid oligomers, protofibrils, and fibrils induce cell death, and antibiotic tetracycline inhibits the fibrillization of beta amyloid peptides and other amyloidogenic proteins and disassembles their pre-formed fibrils. Earlier we have demonstrated that sarcomeric cytoskeletal proteins of the titin family (X-, C-, and H-proteins) are capable to form in vitro amyloid fibrils, and tetracycline effectively destroys these fibrils. Here we show that the viability of polymorphonuclear leukocytes in the presence of X-protein amyloids depends on the concentration of amyloid fibrils of X-protein and the time of incubation. In addition to the disaggregation of X-protein fibrils, tetracycline eliminated the cytotoxic effect of the protein. The antibiotic itself did not show a toxic effect, and the cell viability in its presence even increased. Our results evidence the potential of this approach for evaluating the effectiveness of drugs preventing or treating amyloidoses. 相似文献
19.
The recently published microcrystal structures of amyloid fibrils from small peptides greatly enhanced our understanding of the atomic-level structure of the amyloid fibril. However, only a few amyloid fibrils can form microcrystals. The dansyl-tryptophan fluorescence resonance energy transfer (FRET) pair was shown to be able to detect the inter-peptide arrangement of the Transthyretin (105-115) amyloid fibril. In this study, we combined the known microcrystal structures with the corresponding FRET efficiencies to build a model for amyloid fibril structure classification. We found that fibrils with an antiparallel structural arrangement gave the largest FRET signal, those with a parallel arrangement gave the lowest FRET signal, and those with a mixed arrangement gave a moderate FRET signal. This confirms that the amyloid fibril structure patterns can be classified based on the FRET efficiency. 相似文献
20.
Tamotsu Zako Masafumi Sakono Naomi Hashimoto Masaki Ihara Mizuo Maeda 《Biophysical journal》2009,96(8):3331-3340
Amyloid fibrils are associated with more than 20 diseases, including Alzheimer's disease and type II diabetes. Insulin is a 51-residue polypeptide hormone, with its two polypeptide chains linked by one intrachain and two interchain disulfide bonds, and has long been known to self-assemble in vitro into amyloid fibrils. We demonstrate here that bovine insulin forms flexible filaments in the presence of a reducing agent, Tris (2-carboxyethyl) phosphine. The insulin filaments, possibly formed due to partial reduction of S-S bonds in insulin molecules, differ from intact insulin fibrils in terms of their secondary structure. The insulin filaments were determined to have an antiparallel β-sheet structure, whereas the insulin fibrils have a parallel β-sheet structure. Of importance, the cell toxicity of the insulin filaments was remarkably lower than that of the insulin fibrils. This finding supports the idea that cell toxicity of amyloids correlates with their morphology. The remarkably low toxicity of the filamentous structure should shed new light on possible pharmacological approaches to the various diseases caused by amyloid fibrils. 相似文献