Water Factors In On Amyloid And Prion Aggregation Rates

When aggregation occurs in aqueous solution between amyloid or prion peptides—which are associated with protein-misfolding diseases—a dry interface between the biomolecules forms in two different ways, suggesting how aggregation rates might differ substantially (Proc. Natl. Acad. Sci. USA, DOI: 10.1073/pnas.1008616107). Theoretical models of aggregate formation created by Govardhan Reddy and Devarajan (Dave) Thirumalai of the University of Maryland and John E. Straub of Boston University show that when amyloid β peptide aggregates, fibril formation and expulsion of water from between the joining peptides occur virtually simultaneously. But when the more polar peptides from the yeast prion Sup35 aggregate, long-lived strings of water molecules called “water wires” form in the interface and have to be squeezed out for the dry interface to form, a process that takes additional time. Because of the different dewetting time­scales of the amyloid and prion processes, “we surmise that amyloid fibrils can form nearly 1,000 times faster than prion fibrils,” the researchers write. The study elucidates “the role of water in amyloid fibril assembly and also points the way toward studying water in quasi-one-dimensional confinement,” comments theoretical biophysicist Gerhard Hummer of the National Institutes of Health.