title: In vitro formation of amyloid fibrils from two synthetic peptides of different lengths homologous to Alzheimer's disease beta-protein.
abstract: Two synthetic peptides corresponding to the reported 28-residue sequence of Alzheimer's Disease beta-protein (SP28) and to residues 12-28 (SP17) were used to form fibrils in vitro. Synthetic fibrils bound Congo Red and closely resembled amyloid fibrils isolated from leptomeninges and senile plaques of Alzheimer's brain by electron microscopy. A polyclonal antiserum to SP28 specifically decorated both synthetic and native amyloid by colloidal gold immunoelectron microscopy. Amyloid fibrils isolated from tissue were insoluble on SDS-Polyacrylamide gels, and tended to aggregate while synthetic amyloid fibrils were completely solubilized, releasing only monomers of SP28 and SP17. Anti-SP28 immunostained cerebrovascular and plaque core amyloid, but not neurofibrillary tangles, in tissue section. Western blot analysis showed that anti-SP28 reacted with a 4 kDa band released from amyloid core-enriched preparations and leptomeninges. By contrast, a 16 kDa band corresponding to the tetramer of beta-protein was not recognized. These data suggest that as little as a 17 residue sequence of beta-protein may be required to form fibrils and that the complete sequence of the 4 kDa beta-protein may be important in determining insolubility and the formation of intermediate size polymers.
mesh_terms: D000544:Alzheimer Disease / Q000473:pathology*; D000682:Amyloid / Q000276:immunology / Q000378:metabolism*; D000686:Amyloidosis / Q000473:pathology*; D006801:Humans; D007158:Immunologic Techniques; D008854:Microscopy, Electron; D008970:Molecular Weight; D009419:Nerve Tissue Proteins / Q000276:immunology / Q000378:metabolism*; D009842:Oligopeptides / Q000138:chemical synthesis* / Q000378:metabolism
chemical_list: D000682:Amyloid; D009419:Nerve Tissue Proteins; D009842:Oligopeptides