Solution NMR Studies of the A(1-40) and A
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- 作者：Liming Hou ; Haiyan Shao ; Yongbo Zhang ; Hua Li ; Nanda K. Menon ; Elizabeth B. Neuhaus ; John M. Brewer ; In-Ja L. Byeon ; Dale G. Ray ; Michael P. Vitek ; Takashi Iwashita ; Ronald A. Makula ; Alan B. Przybyla
- 刊名：Journal of the American Chemical Society
- 出版年：2004
- 出版时间：February 25, 2004
- 年：2004
- 卷：126
- 期：7
- 页码：1992 - 2005
- 全文大小：471K
- 年卷期：v.126,no.7(February 25, 2004)
- ISSN：1520-5126
文摘
The pathogenesis of Alzheimer's disease is characterized by the aggregation and fibrillation ofthe 40-residue A
(1-40) and 42-residue A(1-42) peptides into amyloid plaques. The structural changesassociated with the conversion of monomeric A peptide building blocks into multimeric fibrillar -strandaggregates remain unknown. Recently, we established that oxidation of the methionine-35 side chain tothe sulfoxide (Met35red 
Met35ox) significantly impedes the rate of aggregation and fibrillation of the Apeptide. To explore this effect at greater resolution, we carefully compared the 1H, 15N, and 13C NMR chemicalshifts of four A peptides that had the Met35 reduced or oxidized (A(1-40)Met35red, A(1-40)Met35ox,A(1-42)Met35red, and A(1-42)Met35ox). With the use of a special disaggregation protocol, the highlyaggregation prone A peptides could be studied at higher, millimolar concentrations (as required by NMR)in aqueous solution at neutral pH, remaining largely monomeric at 5 
C as determined by sedimentationequilibrium studies. The NOE, amide-NH temperature coefficients, and chemical shift indices of the 1H
,13C, and 13C established that the four peptides are largely random, extended chain structures, with theMet35ox reducing the propensity for -strand structure at two hydrophobic regions (Leu17-Ala21 and Ile31-Val36), and turn- or bendlike structures at Asp7-Glu11 and Phe20-Ser26. Additional NMR studiesmonitoring changes that occur during aging at 37 C established that, along with a gradual loss of signal/noise, the Met35ox significantly hindered upfield chemical shift movements of the 2H NMR signals for theHis6, His13, and His14 side chains. Taken together, the present NMR studies demonstrate that the Met35red Met35ox conversion prevents aggregation by reducing both hydrophobic and electrostatic associationand that the A(1-40)Met35red, A(1-40)Met35ox, A(1-42)Met35red, and A(1-42)Met35ox peptides mayassociate differently, through specific, sharp changes in structure during the initial stages of aggregation.
(1-40) and 42-residue A(1-42) peptides into amyloid plaques. The structural changesassociated with the conversion of monomeric A peptide building blocks into multimeric fibrillar -strandaggregates remain unknown. Recently, we established that oxidation of the methionine-35 side chain tothe sulfoxide (Met35red Met35ox) significantly impedes the rate of aggregation and fibrillation of the Apeptide. To explore this effect at greater resolution, we carefully compared the 1H, 15N, and 13C NMR chemicalshifts of four A peptides that had the Met35 reduced or oxidized (A(1-40)Met35red, A(1-40)Met35ox,A(1-42)Met35red, and A(1-42)Met35ox). With the use of a special disaggregation protocol, the highlyaggregation prone A peptides could be studied at higher, millimolar concentrations (as required by NMR)in aqueous solution at neutral pH, remaining largely monomeric at 5 C as determined by sedimentationequilibrium studies. The NOE, amide-NH temperature coefficients, and chemical shift indices of the 1H,13C, and 13C established that the four peptides are largely random, extended chain structures, with theMet35ox reducing the propensity for -strand structure at two hydrophobic regions (Leu17-Ala21 and Ile31-Val36), and turn- or bendlike structures at Asp7-Glu11 and Phe20-Ser26. Additional NMR studiesmonitoring changes that occur during aging at 37 C established that, along with a gradual loss of signal/noise, the Met35ox significantly hindered upfield chemical shift movements of the 2H NMR signals for theHis6, His13, and His14 side chains. Taken together, the present NMR studies demonstrate that the Met35red Met35ox conversion prevents aggregation by reducing both hydrophobic and electrostatic associationand that the A(1-40)Met35red, A(1-40)Met35ox, A(1-42)Met35red, and A(1-42)Met35ox peptides mayassociate differently, through specific, sharp changes in structure during the initial stages of aggregation.