Topology of the Trans-Membrane Peptide WALP23 in Model Membranes under Negative Mismatch Conditions
Topology of the Trans-Membrane Peptide WALP23 in Model Membranes under Negative Mismatch Conditions
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DOI：
10.1021/jp310056h
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发表时间：
2013-02-28
影响因子：
3.3
通讯作者：
Goldfarb, Daniella
中科院分区：
文献类型：
--
作者：
Matalon, Erez;Kaminker, Ilia;Goldfarb, Daniella
插入膜的螺旋的组织和方向对于更好地理解膜活性肽的作用模式和蛋白质-膜相互作用非常重要。在这里，我们报告了应用 ESEEM（电子自旋回波包络调制）和 DEER（双电子-电子共振）技术在模型膜的疏水核心与肽之间负不匹配的条件下探测 a 螺旋跨膜模型肽 WALP23 的方向和寡聚状态。使用 ESEEM，我们测量了自旋标记的 WALP23 和溶剂 (D2O) 或在胆碱基团上专门氘化的脂质的 H-2 核之间的弱偶极相互作用。使用模型拟合从氘化脂质获得的 ESEEM 数据，该模型提供距膜亲水区域中的 H-2 核层的自旋标签平均距离以及该层中 H-2 核的密度。 DEER 用于通过不同肽上两个自旋标记之间的偶极相互作用来探测寡聚化。我们观察到 WALP23 的中心与双层中板不重合，并且其 N 端比 C 端更埋藏。此外，ESEEM 数据拟合得出的 H-2 层密度远低于预期。 DEER 实验揭示了寡聚物的存在，其存在可归因于负错配和肽的静电偶极子。讨论了寡聚物中各个螺旋的可能排列，该排列与 ESEEM 和 DEER 数据一致。
The organization and orientation of membrane-inserted helices is important for better understanding the mode of action of membrane-active peptides and of protein-membrane interactions. Here we report on the application of ESEEM (electron spin-echo envelope modulation) and DEER (double electron-electron resonance) techniques to probe the orientation and oligomeric state of an a-helical trans-membrane model peptide, WALP23, under conditions of negative mismatch between the hydrophobic cores of the model membrane and the peptide. Using ESEEM, we measured weak dipolar interactions between spin-labeled WALP23 and H-2 nuclei of either the solvent (D2O) or of lipids specifically deuterated at the choline group. The ESEEM data obtained from the deuterated lipids were fitted using a model that provided the spin label average distance from a layer of H-2 nuclei in the hydrophilic region of the membrane and the density of the H-2 nuclei in the layer. DEER was used to probe oligomerization through the dipolar interaction between two spin-labels on different peptides. We observed that the center of WALP23 does not coincide with the bilayer midplane and its N-terminus is more buried than the C-terminus. In addition, the ESEEM data fitting yielded a H-2 layer density that was much lower than expected. The DEER experiments revealed the presence of oligomers, the presence of which was attributable to the negative mismatch and the electrostatic dipole of the peptide. A discussion of a possible arrangement of the individual helices in the oligomers that is consistent with the ESEEM and DEER data is presented.