The Monomeric α-Crystallin Domain of the Small Heat-shock Proteins αB-crystallin and Hsp27 Binds Amyloid Fibril Ends

•Small heat-shock proteins populate a monomer–dimer-oligomer equilibrium.•The alpha-crystallin domain binds at fibril ends to inhibit elongation.•Chaperone-activity is inhibited by disulfide crosslinking at the dimer interface.•Monomers of the alpha-crystallin domain are proposed to interact with fibril ends.