Molecular basis for amyloid fibril formation and stability

Abstract

The molecular structure of the amyloid fibril has remained elusive because of the difficulty of growing well diffracting crystals. By using a sequence-designed polypeptide, we have produced crystals of an amyloid fiber. These crystals diffract to high resolution (1 Å) by electron and x-ray diffraction, enabling us to determine a detailed structure for amyloid. The structure reveals that the polypeptides form fibrous crystals composed of antiparallel ␤-sheets in a cross-␤ arrangement, characteristic of all amyloid fibers, and allows us to determine the side-chain packing within an amyloid fiber. The antiparallel ␤-sheets are zipped together by means of -bonding between adjacent phenylalanine rings and salt-bridges between charge pairs (glutamic acid-lysine), thus controlling and stabilizing the structure. These interactions are likely to be important in the formation and stability of other amyloid fibrils.x-ray diffraction ͉ side-chain packing ͉ structure ͉ -bonding ͉ ␤-sheet interaction

Localization of a Conformational Epitope Common to Non-Native and Fibrillar Immunoglobulin Light Chains

“…Definitive proof of the molecular interactions of mAb 11-1F4 with misfolded LCs will require X-ray crystallographic analyses of F(ab′) 2 11-1F4 complexed with the Len (1-18) peptide, whereas biophysical characterization of the binding of mAb 11-1F4 to native Len (1-18) using CD, NMR, and FRET analyses could lead to further insight into the structural basis for the unique reactivity of this antibody. Future studies to determine the 3D nature of the epitope will contribute to our understanding of amyloid fibril assembly and provide a novel target for the development of antibody-based diagnostic and therapeutic agents for patients with AL amyloidosis.…”

Protein aggregation in bacteria: the thin boundary between functionality and toxicity

“…However, during the lifetime of a protein these APRs may become exposed to a trigger aggregation. b-Aggregation involves nucleation via the formation of intermolecular b-sheets that gives rise to the core of an aggregate (Nelson et al, 2005;Makin et al, 2005). It is thought that intermolecular b-structures derive their great thermodynamic stability from the high degree of hydrogen bond formation of the backbone of the polypeptide chain, but the amino acid side chain configuration will strongly influence the rate of fibril formation (DuBay et al, 2004).…”

Self-assembly in aqueous solution of a modified amyloid beta peptide fragment

“…The crystallization of peptides upon incubation in an aqueous phase has already been noted, for example for KFFEAAAKKFFE which crystallized after incubation of the peptide for several days in a phosphate buffer saline (PBS) aqueous solution. [14] Needle-shape crystals were observed, with lengths in the order of micrometers and diameters in the range ~(12-240) nm [14].…”

“…The sample was partially aligned by stretching the thread before the drying process started, and the resulting XRD pattern ( Figure 7) shows a well-defined "cross-β" pattern 1 with, unusually for amyloid fibrils, multiple orders of reflection. This facilitates determination of the unit cell, which was performed using the software CLEARER [14]. The results provided an orthorhombic unit cell, with unit axis a= 9.6 Å, b= 18.6 Å and c= 43.7 Å.…”