Mapping Aβ Amyloid Fibril Secondary Structure Using Scanning Proline Mutagenesis

Williams, Aaron; Portelius, Erik; Kheterpal, Indu; Guo, Jun‐tao; Cook, Kelsey D.; Xu, Ying; Wetzel, Ronald

doi:10.1016/j.jmb.2003.11.008

Cited by 375 publications

(538 citation statements)

References 54 publications

(56 reference statements)

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“…To further probe the relationship between the conformation of A␤ in fibrils and protofibrils, we turned to scanning proline mutagenesis analysis, which we used previously to provide insights into the A␤ conformation in mature amyloid fibrils (15). Proline point mutants of A␤(1-40) were treated with CLC and the aggregation reactions followed until the amount of A␤ in solution after centrifugation was unchanged (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Peptides (50 M in fibril formation reactions, Ϸ30 M in CLC aggregation reactions) were incubated in PBSA at 37°C. Reaction progress was followed by ThT fluorescence and͞or quantitative HPLC on centrifugation (30 min, 315,000 ϫ g) supernatants of reaction aliquots (12,15). The C r value is the concentration of A␤ in solution when this value stops changing with time.…”

Section: Methodsmentioning

confidence: 99%

“…The C r value is the concentration of A␤ in solution when this value stops changing with time. For amyloid fibril growth, this value represents a position of dynamic equilibrium and is the reciprocal of the growth equilibrium constant for the amyloid fibrils (15); for the CLC-induced aggregation, the value is a more qualitative measure of the stability of the A␤-CLC aggregates. Samples of aggregates were stored at Ϫ80°C after snap-freezing of washed pellets.…”

Section: Methodsmentioning

confidence: 99%

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Structural properties of Aβ protofibrils stabilized by a small molecule

Williams

Sega

Chen

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

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Metastable oligomeric and protofibrillar forms of amyloidogenic proteins have been implicated as on-pathway assembly intermediates in amyloid formation and as the major toxic species in a number of amyloid diseases including Alzheimer's disease. We describe here a chemical biology approach to structural analysis of A␤ protofibrils. Library screening yielded several molecules that stimulate A␤ aggregation. One of these compounds, calmidazolium chloride (CLC), rapidly and efficiently converts A␤(1-40) monomers into clusters of protofibrils. As monitored by electron microscopy, these protofibrils persist for days when incubated in PBS at 37°C, with a slow transition to fibrillar structures apparent only after several weeks. Like normal protofibrils, the CLC-A␤ aggregates exhibit a low thioflavin T response. Like A␤ fibrils, the clustered protofibrils bind the anti-amyloid Ab WO1. The CLC-A␤ aggregates exhibit the same protection from hydrogen-deuterium exchange as do protofibrils isolated from a spontaneous A␤ fibril formation reaction: Ϸ12 of the 39 A␤(1-40) backbone amide protons are protected from exchange in the protofibril, compared with approximately twice that number in amyloid fibrils. Scanning proline mutagenesis analysis shows that the A␤ molecule in these protofibrillar assemblies exhibits the same flexible N and C termini as do mature amyloid fibrils. The major difference in A␤ conformation between fibrils and protofibrils is added structural definition in the 22-29 segment in the fibril. Besides aiding structural analysis, compounds capable of facilitating oligomer and protofibril formation might have therapeutic potential, if they act to sequester A␤ in a form and͞or location that cannot engage the toxic pathway.amyloid ͉ chemical biology ͉ hydrogen exchange ͉ proline scanning

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Structural properties of Aβ protofibrils stabilized by a small molecule

Williams

Sega

Chen

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

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132

131

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“…Structural information concerning amyloid fibrils has, however, been obtained from atomic force microscopy (AFM) [30,31], FTIR [32,33], X-ray fibre diffraction studies [17], cryoelectron microscopy [34,35], hydrogen/deuterium exchange analysed by mass spectrometry and NMR [36][37][38][39] and solid state NMR [40,41]. Important information about both the structures of the aggregates and the mechanism of their formation has also been obtained by using methods such as limited proteolysis [42,43], systematic site-directed mutagenesis [44][45][46], and the analysis of the effects of interactions with specific antibodies. In this review, we focus on the latter technique and show through examples how the use of antibodies, or antibody fragments, can provide unique information concerning the nature of the different steps in amyloid fibril formation described above.…”

Section: The Generic Nature Of the Amyloid Structurementioning

confidence: 99%

Probing the origins, diagnosis and treatment of amyloid diseases using antibodies

Dumoulin

Dobson

2004

Biochimie

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The deposition of proteins in the form of amyloid fibrils is the characteristic feature of more than 20 medical conditions affecting the central nervous system or a variety of peripheral tissues. These disorders, which include Alzheimer's disease, the prion diseases and type II diabetes, are of enormous importance in the context of present-day human health and welfare. Extensive research is therefore being carried out to define the molecular details of the mechanism of the pathological conversion of amyloidogenic proteins from their soluble forms into fibrillar structures. This review focuses on recent studies that demonstrate the power of using antibodies or antibody fragments to probe the process of fibril formation, and discusses the emerging potential of these species as diagnostic and therapeutic agents.

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“…From the standpoint of molecular structure, the defining feature of an amyloid fibril is the presence of cross-β supramolecular structure, meaning that the β-sheets within the fibril are formed by β-strand segments that run approximately perpendicular to the long axis of the fibril and are linked by hydrogen bonds that run approximately parallel to this axis (11)(12)(13). Although determination of the molecular structures of amyloid fibrils is made difficult by their inherent noncrystallinity and insolubility, techniques such as solid state nuclear magnetic resonance (NMR) (12,(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33), electron paramagnetic resonance (EPR) (34)(35)(36), electron microscopy (37)(38)(39)(40)(41)(42)(43), hydrogen/deuterium exchange (29,(44)(45)(46)(47), scanning mutagenesis (48), chemical crosslinking (27,49,50), and x-ray diffraction of amyloid-like crystals …”

mentioning

confidence: 99%

Peptide Conformation and Supramolecular Organization in Amylin Fibrils: Constraints from Solid-State NMR

et al. 2007

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The 37-residue amylin peptide, also known as islet amyloid polypeptide, forms fibrils that are the main peptide or protein component of amyloid that develops in the pancreas of type 2 diabetes patients. Amylin also readily forms amyloid fibrils in vitro that are highly polymorphic under typical experimental conditions. We describe a protocol for the preparation of synthetic amylin fibrils that exhibit a single predominant morphology, which we call a striated ribbon, in electron microscope and atomic force microscope images. Solid state nuclear magnetic resonance (NMR) measurements on a series of isotopically labeled samples indicate a single molecular structure within the striated ribbons. We use scanning transmission electron microscopy and several types of one-dimensional and two-dimensional solid state NMR techniques to obtain constraints on the peptide conformation and supramolecular structure in these amylin fibrils, and derive molecular structural models that are consistent with the experimental data. The basic structural unit in amylin striated ribbons, which we call the protofilament, contains four-layers of parallel β-sheets, formed by two symmetric layers of amylin molecules. The molecular structure of amylin protofilaments in striated ribbons closely resembles the protofilament in amyloid fibrils with similar morphology formed by the 40-residue β-amyloid peptide that is associated with Alzheimer's disease. Keywordsislet amyloid polypeptide; type 2 diabetes; amyloid fibril structure; electron microscopy; atomic force microscopy Amylin, also called islet amyloid polypeptide or IAPP, is a 37-residue peptide that is cosecreted with insulin by the β-cells of pancreas. The normal biological effects of amylin secretion include inhibition of glucagon secretion and reduction of the rate of gastric emptying, effects that contribute to the maintenance of postprandial glucose homeostasis (1). Amylin is the major peptide or protein component of the islet amyloid found in the pancreas of approximately 90% of type 2 (or non-insulin-dependent) diabetes patients (2,3). Fibrillar amylin has been shown * Corresponding author: Dr. Robert Tycko, National Institutes of Health, Building 5, Room 112, Bethesda, MD 20892-0520. phone 301-402-8272. fax 301-496-0825. e-mail robertty@mail.nih.gov.Supporting Information Available HPLC chromatograms from the purification of both reduced and oxidized amylin by reverse-phase chromatography ( Figure S1); FPLC chromatograms from the purification of both human and rodent amylin by size-exclusion chromatography ( Figure S2); 1D 13 C spectra of amylin fibrils with various isotopic labeling patterns, in lyophilized and rehydrated conditions ( Figures S3-S5); Table of 13 C NMR chemical shifts in amylin fibrils, TALOS predictions of backbone torsion angles based on these shifts, and torsion angles determined from 15 N fpRFDR-CT measurements (Table S1). This material is freely available on the World Wide Web at http://www.acs.org. to be toxic to cultured β-cells (4), and has been propo...

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Mapping Aβ Amyloid Fibril Secondary Structure Using Scanning Proline Mutagenesis

Cited by 375 publications

References 54 publications

Structural properties of Aβ protofibrils stabilized by a small molecule

Structural properties of Aβ protofibrils stabilized by a small molecule

Probing the origins, diagnosis and treatment of amyloid diseases using antibodies

Peptide Conformation and Supramolecular Organization in Amylin Fibrils: Constraints from Solid-State NMR

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