A Cyclic Peptide Inhibitor of ApoC-II Peptide Fibril Formation: Mechanistic Insight from NMR and Molecular Dynamics Analysis

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• 作者：Michael D.W. Griffin¹ ; ^{mgriffin@unimelb.edu.au} ; Levi Yeung² ; Andrew Hung² ; Nevena Todorova² ; Yee-Foong Mok¹ ; John A. Karas³ ; Paul R. Gooley¹ ; Irene Yarovsky² ; ^{irene.yarovsky@rmit.edu.au} ; Geoffrey J. Howlett¹
• 关键词：apoC-II ; apolipoprotein C-II ; SE ; sedimentation equilibrium ; MD ; molecular dynamics ; MW ; molecular weight ; NOE ; nuclear Overhauser enhancement ; SASA ; solvent-accessible surface area ; ThT ; thioflavin T
• 刊名：Journal of Molecular Biology
• 出版年：2012
• 期刊代码：102_00222836
• 类别：imm
• 出版时间：9 March, 2012
• 卷：416
• 期：5
• 页码：642-655
• 文件大小：972 K

摘要

The misfolding and aggregation of proteins to form amyloid fibrils is a characteristic feature of several common age-related diseases. Agents that directly inhibit formation of amyloid fibrils represent one approach to combating these diseases. We have investigated the potential of a cyclic peptide to inhibit fibril formation by fibrillogenic peptides from human apolipoprotein C-II (apoC-II). Cyc[60-70] was formed by disulfide cross-linking of cysteine residues added to the termini of the fibrillogenic peptide comprising apoC-II residues 60-70. This cyclic peptide did not self-associate into fibrils. However, substoichiometric concentrations of cyc[60-70] significantly delayed fibril formation by the fibrillogenic, linear peptides apoC-II[60-70] and apoC-II[56-76]. Reduction of the disulfide bond or scrambling the amino acid sequence within cyc[60-70] significantly impaired its inhibitory activity. The solution structure of cyc[60-70] was solved using NMR spectroscopy, revealing a well-defined structure comprising a hydrophilic face and a more hydrophobic face containing the Met60, Tyr63, Ile66 and Phe67 side chains. Molecular dynamics (MD) studies identified a flexible central region within cyc[60-70], while MD simulations of 鈥渟crambled鈥?cyc[60-70] indicated an increased formation of intramolecular hydrogen bonds and a reduction in the overall flexibility of the peptide. Our structural studies suggest that the inhibitory activity of cyc[60-70] is mediated by an elongated structure with inherent flexibility and distinct hydrophobic and hydrophilic faces, enabling cyc[60-70] to interact transiently with fibrillogenic peptides and inhibit fibril assembly. These results suggest that cyclic peptides based on amyloidogenic core peptides could be useful as specific inhibitors of amyloid fibril formation.