Interaction-based evaluation of the propensity for amyloid formation with cross-β structure

In order to reveal the requirements for amino acid sequences prone to form amyloid fibrils, a novel prediction method based on the original structural model of amyloids was developed. As a working hypothesis, two fundamental conditions were introduced into the design of the present system for the evaluation of the propensity for amyloidogenicity. The first of these two conditions was to ensure that the hydrophobic and hydrogen-bonding interactions between residues on neighboring antiparallel β-strands were formed along a fibril axis. The other condition was that the hydrophobic interacting residues appeared on both faces of the protofibril, which gave line-matching interactions. Most peptides with sequences exhibiting high scores, as evaluated by this method, were found to easily form amyloids with the aid of a turn-inducing structure designed as a connection of two β-strands. On the other hand, peptides with low-scoring native sequences and those modified by an internal residue–residue exchange (the latter yielding a null score) did not lead to amyloid formation. These data demonstrated the validity of this method for the prediction of amyloid structures. Moreover, the present study provided support for the proposed model of the essential structure associated with the above working hypothesis. The predicted high-scoring regions were in good agreement with the putative amyloid core regions reported thus far.