Molecular Alignment within β-Sheets in Aβ14-23 Fibrils: Solid-State NMR Experiments and Theoretical Predictions

Bu, Zimei; Shi, Yuan; Callaway, David J.E.; Tycko, Robert

doi:10.1529/biophysj.106.091017

Cited by 47 publications

(64 citation statements)

References 81 publications

(154 reference statements)

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“…Figure 4C shows the 2D 13 C NMR spectrum of morphologically homogeneous AMY05 fibrils in the dry, lyophilized state. Crosspeaks in Figure 4C are broader than in Figure 4B, as observed in previous solid state NMR studies of other amyloid fibrils when comparing lyophilized and hydrated states of the same sample (18,19,22,77,78). Line-narrowing in the hydrated state is attributed to increased molecular motions, which partially average out the inhomogeneous broadening of NMR chemical shifts that is present in all noncrystalline solids.…”

Section: Characterization Of Secondary Structure By 13 C Nmrsupporting

confidence: 74%

“…In light of current knowledge that the ability to form amyloid fibrils is not an unusual property for a peptide (10), the fact that short peptides representing residues 20-29 form fibrils (56,89) does not imply that this segment constitutes the core of full-length amylin fibrils. In fact, the molecular structures of fibrils formed by short peptides can be qualitatively different from the structures of the corresponding segments in the context of full-length peptide fibrils, as demonstrated by findings that certain β-amyloid fragments form antiparallel β-sheets in amyloid fibrils (16,19,24,78), while other fragments (15,26,27) and full-length β-amyloid (15,17,21) form parallel β-sheets. Evidence from Griffiths et al for antiparallel β-sheets in fibrils formed by residues 20-29 of human amylin (25) indicates that, as in the case of β-amyloid fibrils, the molecular structures in fibrils formed by amylin fragments need not reflect the molecular structure of full-length amylin fibrils.…”

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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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Section: Characterization Of Secondary Structure By 13 C Nmrsupporting

confidence: 74%

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confidence: 99%

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

et al. 2007

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“…20,64 The N/CHHC data presented here indicate that the polyglutamine fibrils investigated consist mainly of antiparallel β-sheets, in line with structural studies on shorter peptides that were also observed to adopt an antiparallel organization. [68][69][70][71][72] These findings may be a direct consequence of electrostatic interactions that favor an antiparallel arrangement of the charged peptide termini.…”

Section: Discussionmentioning

confidence: 99%

Structural Characterization of Polyglutamine Fibrils by Solid-State NMR Spectroscopy

Schneider

Schumacher

Mueller

et al. 2011

Journal of Molecular Biology

160

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Protein aggregation via polyglutamine stretches occurs in a number of severe neurodegenerative diseases such as Huntington's disease. We have investigated fibrillar aggregates of polyglutamine peptides below, at, and above the toxicity limit of around 37 glutamine residues using solid-state NMR and electron microscopy. Experimental data are consistent with a dry fibril core of at least 70-80 Å in width for all constructs. Solid-state NMR dipolar correlation experiments reveal a largely β-strand character of all samples and point to tight interdigitation of hydrogen-bonded glutamine side chains from different sheets. Two approximately equally frequent populations of glutamine residues with distinct sets of chemical shifts are found, consistent with local backbone dihedral angles compensating for β-strand twist or with two distinct sets of side-chain conformations. Peptides comprising 15 glutamine residues are present as single extended β-strands. Data obtained for longer constructs are most compatible with a superpleated arrangement with individual molecules contributing β-strands to more than one sheet and an antiparallel assembly of strands within β-sheets.

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“…Electron spin resonance studies showed in-register parallel ␤-sheet structures of amylin (26), ␣-synuclein (Parkinson's disease) (27), and Tau (Alzheimer's disease and other 'tauopathies') (28). Some fragments of pathogenic peptides and crystal structures of peptides capable of forming amyloid filaments are found to have antiparallel or parallel structures (29)(30)(31)(32)(33), and recently the D23N mutant of A␤ has been found to adopt an antiparallel structure (34). In contrast, the Podospora prion [Het-s] is based on amyloid of the HET-s protein with a ␤-helical structure (35,36).…”

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The repeat domain of the melanosome fibril protein Pmel17 forms the amyloid core promoting melanin synthesis

McGlinchey¹,

Shewmaker²,

McPhie³

et al. 2009

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

133

153

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Pmel17 is a melanocyte protein necessary for eumelanin deposition 1 in mammals and found in melanosomes in a filamentous form. The luminal part of human Pmel17 includes a region (RPT) with 10 copies of a partial repeat sequence, pt.e.gttp.qv., known to be essential in vivo for filament formation. We show that this RPT region readily forms amyloid in vitro, but only under the mildly acidic conditions typical of the lysosome-like melanosome lumen, and the filaments quickly become soluble at neutral pH. Under the same mildly acidic conditions, the Pmel filaments promote eumelanin formation. Electron diffraction, circular dichroism, and solidstate NMR studies of Pmel17 filaments show that the structure is rich in beta sheet. We suggest that RPT is the amyloid core domain of the Pmel17 filaments so critical for melanin formation.

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Molecular Alignment within β-Sheets in Aβ14-23 Fibrils: Solid-State NMR Experiments and Theoretical Predictions

Cited by 47 publications

References 81 publications

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

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

Structural Characterization of Polyglutamine Fibrils by Solid-State NMR Spectroscopy

The repeat domain of the melanosome fibril protein Pmel17 forms the amyloid core promoting melanin synthesis

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