Vibrational coupling, isotopic editing, and β-sheet structure in a membrane-bound polypeptide
Vibrational coupling, isotopic editing, and β-sheet structure in a membrane-bound polypeptide
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DOI：
10.1021/ja038869f
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发表时间：
2004-05-12
影响因子：
15
通讯作者：
Axelsen, PH
中科院分区：
文献类型：
--
作者：
Paul, C;Wang, JP;Axelsen, PH
n -乙酰化的六肽wllll （AcWL5）分裂进入脂质膜，并被认为组装成一个反平行的β -片。作为这种结构分配的测试，残基2-6的肽键被标记为C-13，并被允许吸附在支撑的脂质膜上。用内反射红外光谱法检查了与膜结合的肽在相邻β链中标记振动模式之间耦合的证据。实验结果表明，在D2O中，由于C-13引起的酰胺I吸收带（即酰胺I'）选择性增强，当标签位于肽主链上的任何一个位置时。采用具有贯穿键和贯穿空间相互作用的激子模型对AcWL5模型进行了平行和反平行β -片构型的模拟。模拟得到的光谱与实验结果吻合较好，说明了C-13波段强度和频带频率的增强。它们还有助于深入了解同位素编辑光谱中出现的独特酰胺I带形状的物理起源和结构选择性。结果表明，膜结合AcWL5形成的P-sheet确实是反平行的，这些肽的红外光谱中C-13波段的增强是由链间和链内耦合到C-12模式引起的。
The N-acetylated hexapeptide WLLLLL (AcWL5) partitions into lipid membranes and is believed to assemble into an antiparallel beta-sheet. As a test of this structural assignment, the peptide bonds of residues 2-6 were labeled with C-13 and allowed to adsorb onto a supported lipid membrane. Peptides bound to the membrane were examined for evidence of coupling between the labeled vibrational modes in adjacent beta-strands with internal reflection infrared spectroscopy. Experimental results indicate that the amide I absorption band in D2O (i.e., amide I') attributable to C-13 is selectively enhanced when the label is at any one of several positions along the peptide backbone. Simulations employing an excitonic model with through-bond and through-space interactions were performed on AcWL5 models in parallel and antiparallel beta-sheet configurations. The simulations yield spectra in good agreement with the experimental results, accounting for the enhancement of both C-13 band intensities and band frequencies. They also yield insight into the physical origin and structure selectivity of the distinctive amide I' band shapes that arise in isotopically edited spectra. It is concluded that the P-sheet formed by membrane-bound AcWL5 is indeed antiparallel, and the enhancement of C-13 bands in the infrared spectra of these peptides is caused by both interstrand and intrastrand coupling to C-12 modes.