αB-crystallin affects the morphology of Aβ(1-40) aggregates

B-crystallin (ABC) is a human small heat shock protein that is strongly linked to Alzheimers disease (AD). In vitro, it can inhibit the aggregation and amyloid formation of a range of proteins including A{beta}(1-40), a primary component of AD amyloid plaques. Despite the strong links, the mechanism by which ABC inhibits amyloid formation has remained elusive, in part due to the notorious irreproducibility of aggregation assays involving preparations of A{beta}-peptides of native sequence. Here, we present a recombinant expression protocol to produce native A{beta}(1-40), devoid of any modifications or exogenous residues, with yields up to 4 mg/L E. coli. This material provides highly reproducible aggregation kinetics and, by varying the solution conditions, we obtain either highly ordered amyloid fibrils or more disordered aggregates. Addition of ABC slows the aggregation of A{beta}(1-40), and interferes specifically with the formation of ordered amyloid fibrils, favouring instead the more disordered aggregates. Solution-state NMR spectroscopy reveals that the interaction of ABC with A{beta}(1-40) depends on the specific aggregate morphology. These results provide mechanistic insight into how ABC inhibits the formation of amyloid fibrils. HighlightsO_LIProtocol for production of native recombinant A{beta}(1-40) C_LIO_LIAmyloid formation under physiological conditions is highly reproducible C_LIO_LIBoth ordered fibrils and disordered aggregates can be reliably formed C_LIO_LIB-crystallin specifically inhibits amyloid fibril assembling, favouring disordered aggregates C_LI eTOC blurbMuller et al. introduce a protocol for the highly reproducible production of amyloid from native A{beta}(1-40) and determine that the human chaperone ABC specifically destabilises them in favour of disordered aggregates. NMR shows that ABC can distinguish between aggregate morphologies. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=195 HEIGHT=200 SRC="FIGDIR/small/433908v1_ufig1.gif" ALT="Figure 1"> View larger version (69K): org.highwire.dtl.DTLVardef@fe31fborg.highwire.dtl.DTLVardef@8367aforg.highwire.dtl.DTLVardef@10c42a3org.highwire.dtl.DTLVardef@1eaddeb_HPS_FORMAT_FIGEXP M_FIG C_FIG