Amyloid Formation

Amyloids are β-sheet rich fibrillar protein structures that result from the self-assembly of polypeptides and proteins. A wide range of proteins are known to form amyloid fibrils in vivo and an even larger number do so in vitro. More than 20 different human diseases involve amyloid formation, and the amyloid fibril or intermediates populated during its assembly are cytotoxic. All amyloid fibrils share common structural features despite exhibiting considerable variation in primary sequence. These features include a crossed β-sheet organization in which the individual β-strands are arranged perpendicular to the fiber axis such that the hydrogen bonds are oriented parallel to the fibril axis, resistance to proteolysis, and the ability to bind to certain dyes. Normally, the aggregation of proteins into amyloid is a pathological event; however, evidence indicates that naturally occurring amyloids may also play a beneficial biological role in vivo.