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• 作者：Adam L. Cloe ; Joseph P. R. O. Orgel ; Joseph R. Sachleben ; Robert Tycko ; Stephen C. Meredith
• 刊名：Biochemistry
• 出版年：2011
• 出版时间：March 29, 2011
• 年：2011
• 卷：50
• 期：12
• 页码：2026-2039
• 全文大小：1294K
• 年卷期：v.50,no.12(March 29, 2011)
• ISSN：1520-4995

文摘

The 螖E693 (Japanese) mutation of the 尾-amyloid precursor protein leads to production of 螖E22-A尾 peptides such as 螖E22-A尾_1鈭?9. Despite reports that these peptides do not form fibrils, here we show that, on the contrary, the peptide forms fibrils essentially instantaneously. The fibrils are typical amyloid fibrils in all respects except that they cause only low levels of thioflavin T (ThT) fluorescence, which, however, develops with no lag phase. The fibrils bind ThT, but with a lower affinity and a smaller number of binding sites than wild-type (WT) A尾_1鈭?0. Fluorescence depolarization confirms extremely rapid aggregation of 螖E22-A尾_1鈭?9. Size exclusion chromatography (SEC) indicates very low concentrations of soluble monomer and oligomer, but only in the presence of some organic solvent, e.g., 2% (v/v) DMSO. The critical concentration is approximately 1 order of magnitude lower for 螖E22-A尾_1鈭?9 than for WT A尾_1鈭?0. Several lines of evidence point to an altered structure for 螖E22-A尾_1鈭?9 compared to that of WT A尾_1鈭?0 fibrils. In addition to differences in ThT binding and fluorescence, PITHIRDS-CT solid-state nuclear magnetic resonance (NMR) measurements of 螖E22-A尾_1鈭?9 are not compatible with the parallel in-register 尾-sheet generally observed for WT A尾_1鈭?0 fibrils. X-ray fibril diffraction showed different D spacings: 4.7 and 10.4 脜 for WT A尾_1鈭?0 and 4.7 and 9.6 脜 for 螖E22-A尾_1鈭?9. Equimolar mixtures of 螖E22-A尾_1鈭?9 and WT A尾_1鈭?0 also produced fibrils extremely rapidly, and by the criteria of ThT fluorescence and electron microscopic appearance, they were the same as fibrils made from pure 螖E22-A尾_1鈭?9. X-ray diffraction of fibrils formed from 1:1 molar mixtures of 螖E22-A尾_1鈭?9 and WT A尾_1鈭?0 showed the same D spacings as fibrils of the pure mutant peptide, not the wild-type peptide. These findings are consistent with extremely rapid nucleation by 螖E22-A尾_1鈭?9, followed by fibril extension by WT A尾_1鈭?0, and 鈥渃onversion鈥?of the wild-type peptide to a structure similar to that of the mutant peptide, in a manner reminiscent of the prion conversion phenomenon.