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by Keyword: Amyloid formation


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Sabaté, R., Espargaró, A., de Groot, N. S., Valle-Delgado, J. J., Fernàndez-Busquets, X., Ventura, S., (2010). The role of protein sequence and amino acid composition in amyloid formation: Scrambling and backward reading of IAPP amyloid fibrils Journal of Molecular Biology , 404, (2), 337-352

The specific functional structure of natural proteins is determined by the way in which amino acids are sequentially connected in the polypeptide. The tight sequence/structure relationship governing protein folding does not seem to apply to amyloid fibril formation because many proteins without any sequence relationship have been shown to assemble into very similar β-sheet-enriched structures. Here, we have characterized the aggregation kinetics, seeding ability, morphology, conformation, stability, and toxicity of amyloid fibrils formed by a 20-residue domain of the islet amyloid polypeptide (IAPP), as well as of a backward and scrambled version of this peptide. The three IAPP peptides readily aggregate into ordered, β-sheet-enriched, amyloid-like fibrils. However, the mechanism of formation and the structural and functional properties of aggregates formed from these three peptides are different in such a way that they do not cross-seed each other despite sharing a common amino acid composition. The results confirm that, as for globular proteins, highly specific polypeptide sequential traits govern the assembly pathway, final fine structure, and cytotoxic properties of amyloid conformations.

Keywords: Amyloid formation, Islet amyloid polypeptide, Protein aggregation, Protein sequence, Retro proteins


Arimon, M., Grimminger, V., Sanz, F., Lashuel, H. A., (2008). Hsp104 targets multiple intermediates on the amyloid pathway and suppresses the seeding capacity of A beta fibrils and protofibrils Journal of Molecular Biology , 384, (5), 1157-1173

The heat shock protein Hsp104 has been reported to possess the ability to. modulate protein aggregation and toxicity and to "catalyze" the disaggregation and recovery of protein aggregates, including amyloid fibrils, in yeast, Escherichia coli, mammalian cell cultures, and animal models of Huntington's disease and Parkinson's disease. To provide mechanistic insight into the molecular mechanisms by which Hsp104 modulates aggregation and fibrillogenesis, the effect of Hsp104 on the fibrillogenesis of amyloid beta (A(3) was investigated by characterizing its ability to interfere with oligomerization and fibrillogenesis of different species along the amyloid-formation pathway of A beta. To probe the disaggregation activity of Hsp104, its ability to dissociate preformed protofibrillar and fibrillar aggregates of A beta was assessed in the presence and in the absence of ATP. Our results show that Hsp104 inhibits the fibrillization of monomeric and protofibrillar forms of A beta in a concentration-dependent but ATP-independent manner. Inhibition of A beta fibrillization by Hsp104 is observable up to Hsp104/A beta stoichiometric ratios of 1:1000, suggesting a preferential interaction of Hsp104 with aggregation intermediates (e.g., oligomers, protofibrils, small fibrils) on the pathway of A beta amyloid formation. This hypothesis is consistent with our observations that Hsp104 (i) interacts with A beta protofibrils, (ii) inhibits conversion of protofibrils into amyloid fibrils, (iii) arrests fibril elongation and reassembly, and (iv) abolishes the capacity of protofibrils and sonicated fibrils to seed the fibrillization of monomeric A beta. Together, these findings suggest that the strong inhibition of A beta fibrillization by Hsp104 is mediated by its ability to act at different stages and target multiple intermediates on the pathway to amyloid formation.

Keywords: Amyloid formation A beta, Hsp104, Disaggregation, Alzheimer's diseases