A Protofibrils Possess a Stable Core Structure Resistant to Hydrogen Exchange

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• 作者：Indu Kheterpal ; Hilal A. Lashuel ; Dean M. Hartley ; Thomas Walz ; Peter T. Lansbury Jr. ; and Ronald Wetzel
• 刊名：Biochemistry
• 出版年：2003
• 出版时间：December 9, 2003
• 年：2003
• 卷：42
• 期：48
• 页码：14092 - 14098
• 全文大小：281K
• 年卷期：v.42,no.48(December 9, 2003)
• ISSN：1520-4995

文摘

Protofibrils are transient structures observed during in vitro formation of mature amyloid fibrilsand have been implicated as the toxic species responsible for cell dysfunction and neuronal loss inAlzheimer's disease (AD) and other protein aggregation diseases. To better understand the roles ofprotofibrils in amyloid assembly and Alzheimer's disease, we characterized secondary structural featuresof these heterogeneous and metastable assembly intermediates. We chromatographically isolated differentsize populations of protofibrils from amyloid assembly reactions of Amages/gifchars/beta2.gif" BORDER=0 ALIGN="middle">(1-40), both wild type and theArctic variant associated with early onset familial AD, and exposed them to hydrogen-deuterium exchangeanalysis monitored by mass spectrometry (HX-MS). We show that HX-MS can distinguish amongunstructured monomer, protofibrils, and fibrils by their different protection patterns. We find that about40% of the backbone amide hydrogens of Amages/gifchars/beta2.gif" BORDER=0 ALIGN="middle"> protofibrils are highly resistant to exchange with deuteriumeven after 2 days of incubation in aqueous deuterated buffer, implying a very stable, presumably H-bonded,core structure. This is in contrast to mature amyloid fibrils, whose equally stable structure protects about60% of the backbone amide hydrogens over the same time frame. We also find a surprising degree ofspecificity in amyloid assembly, in that wild type Amages/gifchars/beta2.gif" BORDER=0 ALIGN="middle"> is preferentially excluded from both protofibrilsand fibrils grown from an equimolar mixture of wild type and Arctic mutant peptides. These and otherdata are interpreted and discussed in terms of the role of protofibrils in fibril assembly and in disease.