Topology of the Trans-Membrane Peptide WALP23 in Model Membranes under Negative Mismatch Conditions

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• 作者：Erez Matalon ; Ilia Kaminker ; Herbert Zimmermann ; Miriam Eisenstein ; Yechiel Shai ; Daniella Goldfarb
• 刊名：The Journal of Physical Chemistry B
• 出版年：2013
• 出版时间：February 28, 2013
• 年：2013
• 卷：117
• 期：8
• 页码：2280-2293
• 全文大小：545K
• 年卷期：v.117,no.8(February 28, 2013)
• ISSN：1520-5207

文摘

The organization and orientation of membrane-inserted helices is important for better understanding the mode of action of membrane-active peptides and of protein鈥搈embrane interactions. Here we report on the application of ESEEM (electron spin鈥揺cho envelope modulation) and DEER (double electron鈥揺lectron resonance) techniques to probe the orientation and oligomeric state of an 伪-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 ²H 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 ²H nuclei in the hydrophilic region of the membrane and the density of the ²H 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 ²H 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.