Abstract

Understanding how different proteins assemble into the ordered, insoluble aggregates associated with amyloid disease is a formidable challenge. Whilst it is generally accepted that protein unfolding is required for the formation of amyloid fibrils from natively folded proteins in vitro and, therefore, presumably also in vivo, the point at which the folding and aggregation free energy landscapes diverge, and the role of different amino acid residues in determining folding versus aggregation, remain obscure. Even more challenging is the identification of early oligomeric species and their structural characterisation, since such species are aggregation-prone, short-lived and rapidly equilibrating. Using an array of different biophysical methods and approaches, I will describe our recent experiments which have used NMR paramagnetic relaxation experiments, alongside other biophysical methods, to reveal the mechanism by which conformational conversion of the normally soluble protein, beta-2-microglobulin into an amyloidogenic conformation occurs and how bimolecular collisions between protein variants can result in very different outcomes of assembly. The insights gained may help to derive new routes to the modulation of aggregation and lead to fascinating questions about the cooperativity of protein structures and how this modulates their behaviours in assembly.