β‐amyloid model core peptides: Effects of hydrophobes and disulfides

Abstract

The mechanism by which a disordered peptide nucleates and forms amyloid is incompletely understood. A central domain of β-amyloid (Aβ21-30) has been proposed to have intrinsic structural propensities that guide the limited formation of structure in the process of fibrillization. In order to test this hypothesis, we examine several internal fragments of Aβ, and variants of these either cyclized or with an N-terminal Cys. While Aβ21-30 and variants were always monomeric and unstructured (circular dichroism (CD) and nuclear magnetic resonance spectroscopy (NMRS)), we found that the addition of flanking hydrophobic residues in Aβ16-34 led to formation of typical amyloid fibrils. NMR showed no long-range nuclear overhauser effect (nOes) in Aβ21-30, Aβ16-34, or their variants, however. Serial 1 H-15 N-heteronuclear single quantum coherence spectroscopy, 1 H-1 H nuclear overhauser effect spectroscopy, and 1 H-1 H total correlational spectroscopy spectra were used to follow aggregation of Aβ16-34 and Cys-Aβ16-34 at a site-specific level. The addition of an N-terminal Cys residue (in Cys-Aβ16-34) increased the rate of fibrillization which was attributable to disulfide bond formation. We propose a scheme comparing the aggregation pathways for Aβ16-34 and Cys-Aβ16-34, according to which Cys-Aβ16-34 dimerizes, which accelerates fibril formation. In this context, cysteine residues form a focal point that guides fibrillization, a role which, in native peptides, can be assumed by heterogeneous nucleators of aggregation.

Intein-mediated recombinant expression of monomeric B22Asp desB30 insulin

“…Since misformed disulfides will induce lower solubility [25][26][27], faster degradation [28,29], and unwanted aggregation or precipitation [30,31], our final product displayed excellent solubility and superior stability, compared to commercially available insulin (Fig. 7), indicating no evidence of any misformed disulfides.…”

Ruthenium complexes bearing glucosyl ligands are able to inhibit the amyloid aggregation of short histidine-peptides

“…Generally, penta-and hexa-peptides as fragments of neurodegenerative proteins were demonstrated to self-assemble, and form amyloids with various morphologies 43,44 that partially recapitulate the aggregation process of larger proteins. 45,46 Herein, we analyzed two different short protein fragments bearing one His residue, assumed as amyloid models, that were both uncharged at neutral pH (Table 1): (i) the fragment 27-32 of the human Bloom syndrome protein (BSP 27-32 ), 47 and (ii) the 103-108 segment of human beta-2-microglobulin that becomes 83-88 (β 2 m 83-88 ), after proteolytic cleavage. 43 Both protein fragments, not present in vivo, were identified as aggregation-prone regions (APRs) through prediction and experimental studies.…”

Elucidating the Oligomerization and Cellular Interactions of a Trimer Derived from Aβ through Fluorescence and Mass Spectrometric Studies

“…Model systems of stabilized Aβ-derived oligomers have emerged as tools to better understand endogenous oligomers and provide further insight into the molecular basis of Alzheimer’s disease. − Our laboratory has developed a series of covalently stabilized trimers derived from residues 17–36 of Aβ as chemical models of toxic amyloid oligomers associated with neurodegeneration in Alzheimer’s disease. − One of the trimers, termed 4AT-L, is composed of three β-hairpins formed by an Aβ 17–36 peptide, with molecular templates designed to induce β-hairpin folding, block uncontrolled aggregation, and allow disulfide crosslinking of three β-hairpins to form a covalent trimer . Trimer 4AT-L is toxic toward the neuronal cell line SH-SY5Y, assembles to form ball-shaped dodecamers composed of four trimers in the crystal state, and forms dodecamers in SDS-PAGE.…”