Sivanesam K, Byrne A, Bisaglia M, Bubacco L, Andersen N
Department of Chemistry, University of Washington, Seattle, WA 98195.
Department of Biology, University of Padua, 35121 Padova, Italy.
RSC Adv. 2015;5(15):11577-11590. doi: 10.1039/C5RA00325C.
Further examination of peptides with well-folded antiparallel β strands as inhibitors of amyloid formation from α-synuclein has resulted in more potent inhibitors. Several of these had multiple Tyr residues and represent a new lead for inhibitor design by small peptides that do not divert α-synuclein to non-amyloid aggregate formation. The most potent inhibitor obtained in this study is a backbone cyclized version of a previously studied β hairpin, designated as WW2, with a cross-strand Trp/Trp cluster. The cyclization was accomplished by adding a d-Pro-l-Pro turn locus across strand termini. At a 2:1 peptide to α-synuclein ratio, cyclo-WW2 displays complete inhibition of β-structure formation. Trp-bearing antiparallel β-sheets held together by a disulphide bond are also potent inhibitors. N HSQC spectra of α-synuclein provided new mechanistic details. The time course of N HSQC spectral changes observed during β-oligomer formation has revealed which segments of the structure become part of the rigid core of an oligomer at early stages of amyloidogenesis and that the C-terminus remains fully flexible throughout the process. All of the effective peptide inhibitors display binding-associated titration shifts in N HSQC spectra of α-synuclein in the C-terminal Q109-E137 segment. Cyclo-WW2, the most potent inhibitor, also displays titration shifts in the G41-T54 span of α-synuclein, an additional binding site. The earliest aggregation event appears to be centered about H50 which is also a binding site for our most potent inhibitor.
进一步研究具有良好折叠的反平行β链的肽作为α-突触核蛋白淀粉样蛋白形成的抑制剂，已产生了更有效的抑制剂。其中几种具有多个酪氨酸残基，代表了通过小肽进行抑制剂设计的新线索，这些小肽不会使α-突触核蛋白转向非淀粉样蛋白聚集体的形成。本研究中获得的最有效抑制剂是先前研究的β发夹的主链环化版本，命名为WW2，具有跨链色氨酸/色氨酸簇。环化是通过在链末端添加一个d-脯氨酸-l-脯氨酸转角位点来完成的。在肽与α-突触核蛋白的比例为2:1时，环化WW2对β结构的形成表现出完全抑制作用。由二硫键连接的含色氨酸的反平行β片层也是有效的抑制剂。α-突触核蛋白的N HSQC光谱提供了新的作用机制细节。在β-寡聚体形成过程中观察到的N HSQC光谱变化的时间进程揭示了在淀粉样蛋白生成的早期阶段，结构的哪些片段成为寡聚体刚性核心的一部分，并且C末端在整个过程中保持完全灵活。所有有效的肽抑制剂在α-突触核蛋白C末端Q109-E137片段的N HSQC光谱中均显示出与结合相关的滴定位移。最有效的抑制剂环化WW2在α-突触核蛋白的G41-T54区域也显示出滴定位移，这是另一个结合位点。最早的聚集事件似乎集中在H50周围，H50也是我们最有效抑制剂的结合位点。
