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首页> 外文期刊>Chemistry: A European journal >A designed three-stranded β-sheet in an α/β hybrid peptide
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A designed three-stranded β-sheet in an α/β hybrid peptide

机译：设计的α/β杂合肽中的三链β-折叠

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摘要

The incorporation of β-amino acid residues into the antiparallel β-strand segments of a multi-stranded β-sheet peptide is demonstrated for a 19-residue peptide, Boc-LVβFVDPGL βFVVLDPGLVLβFVV-OMe (BBH19). Two centrally positioned DPro-Gly segments facilitate formation of a stable three-stranded β-sheet, in which β-phenylalanine (βPhe) residues occur at facing positions 3, 8 and 17. Structure determination in methanol solution is accomplished by using NMR-derived restraints obtained from NOEs, temperature dependence of amide NH chemical shifts, rates of H/D exchange of amide protons and vicinal coupling constants. The data are consistent with a conformationally well-defined three-stranded β-sheet structure in solution. Cross-strand interactions between βPhe3/βPhe17 and βPhe3/Val15 residues define orientations of these side-chains. The observation of close contact distances between the side-chains on the N- and C-terminal strands of the three-stranded β-sheet provides strong support for the designed structure. Evidence is presented for multiple side-chain conformations from an analysis of NOE data. An unusual observation of the disappearance of the Gly NH resonances upon prolonged storage in methanol is rationalised on the basis of a slow aggregation step, resulting in stacking of three-stranded β-sheet structures, which in turn influences the conformational interconversion between type I′ and type II′ β-turns at the two DPro-Gly segments. Experimental evidence for these processes is presented. The decapeptide fragment Boc-LVβFVDPGL βFVV-OMe (BBH10), which has been previously characterized as a type I′ β-turn nucleated hairpin, is shown to favour a type II′ β-turn conformation in solution, supporting the occurrence of conformational interconversion at the turn segments in these hairpin and sheet structures.
机译：对于19个残基的肽Boc-LVβFVDPGLβFVVLDPGLVLβFVV-OMe（BBH19），证明了将β-氨基酸残基掺入多链β-折叠肽的反平行β链片段中。两个居中定位的DPro-Gly片段有助于形成稳定的三链β-折叠，其中β-苯丙氨酸（βPhe）残基出现在面对位置3、8和17处。通过使用NMR衍生来确定甲醇溶液中的结构从NOE获得的限制，酰胺NH的化学位移的温度依赖性，酰胺质子的H / D交换速率和邻位耦合常数。数据与溶液中构象明确的三链β-折叠结构一致。 βPhe3/βPhe17和βPhe3/ Val15残基之间的交叉链相互作用定义了这些侧链的方向。观察到三链β-折叠的N端和C端链的侧链之间的紧密接触距离，为设计结构提供了有力的支持。通过对NOE数据的分析，提供了多个侧链构象的证据。在缓慢的聚集步骤的基础上，合理地观察到了在甲醇中长时间储存​​后Gly NH共振消失的异常现象，从而导致三链β-折叠结构的堆叠，进而影响了I'型之间的构象互变II型β'在两个DPro-Gly节段转弯。提供了这些过程的实验证据。十肽片段Boc-LVβFVDPGLβFVV-OMe（BBH10）先前已被表征为I'型β圈有核发夹，显示其在溶液中具有II'型β圈构象，从而支持构象互变的发生在这些发夹和薄片结构的转弯处。

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