The emerging concept of functional amyloid

Although amyloid has usually been considered a pathological structure, growing evidence indicates that amyloid may also be a productive part of cell biology contributing to normal physiology. In fact, amyloid formation seems to be an intrinsic propensity of polypeptides in general and the amyloid beta-fold an evolutionary highly conserved structure. Functional amyloids have been found in a wide range of organisms, from bacteria to mammals, with functions as diverse as biofilm formation, development of aerial structures, scaffolding, regulation of melanin synthesis, epigenetic control of polyamines and information transfer. Obviously, organisms have evolved taking advantage of the canonical amyloid beta-sheet fold, a conformation that possesses both high resistance to proteolysis, self-replicative properties and capability to function as a molecular memory.