Department of Chemistry and Biochemistry, University of North Carolina, Wilmington, NC 28403, United States of America.
Department of Chemistry and Biochemistry, University of North Carolina, Wilmington, NC 28403, United States of America.
Biochim Biophys Acta Biomembr. 2024 Jan;1866(1):184218. doi: 10.1016/j.bbamem.2023.184218. Epub 2023 Aug 25.
Transportan 10 (TP10) is a 21-residue, cationic, α-helical cell-penetrating peptide that can be used as a delivery vector for various bioactive molecules. Based on recent confocal microscopy studies, it is believed that TP10 can translocate across neutral lipid membrane passively, possibly as a monomer, without the formation of permanent pore. Here, we performed extensive molecular dynamics (MD) simulations of TP10W (Y3W variant of TP10) to find the microscopic details of binding, folding and insertion of TP10W to transmembrane state in POPC bilayer. Binding study with CHARMM36 force field showed that TP10W initially binds to the membrane surface in unstructured configuration, but it spontaneously folds into α-helical conformation under the lipid head groups. Further insertion of TP10W, changing from a surface bound state to a vertically oriented transmembrane state, was investigated via umbrella simulations. The resulting free energy profile shows a relatively small barrier between two states, suggesting a possible translocation pathway as a monomer. In fact, unbiased simulation of transmembrane TP10W revealed how a charged Lys side chain can move from one leaflet to the other without a significant free energy cost. Finally, we compared the results of TP10W simulations with those of point mutated variants (TP10W-K12A18 and TP10W-K19L) to understand the effect of charge distribution on the peptide. It was observed that such a conservative mutation can cause noticeable changes in the conformations of both surface bound and transmembrane states. The results of present study will be discussed in relation to the experimentally observed activities of TP10W against neutral membrane.
转运蛋白 10（TP10）是一种 21 个残基的阳离子α-螺旋细胞穿透肽，可作为各种生物活性分子的递药载体。基于最近的共聚焦显微镜研究，人们认为 TP10 可以被动地穿过中性脂质膜转运，可能作为单体，而不会形成永久性孔。在这里，我们对 TP10W（TP10 的 Y3W 变体）进行了广泛的分子动力学（MD）模拟，以找到 TP10W 与 POPC 双层膜中跨膜状态结合、折叠和插入的微观细节。用 CHARMM36 力场进行的结合研究表明，TP10W 最初以无规卷曲的构象结合到膜表面，但在脂质头基下自发折叠成α-螺旋构象。进一步通过伞状模拟研究了 TP10W 从表面结合状态到垂直取向的跨膜状态的插入。所得的自由能曲线表明两个状态之间的势垒相对较小，这表明可能存在单体的转运途径。事实上，对跨膜 TP10W 的无偏模拟揭示了带电荷的赖氨酸侧链如何在没有显著自由能成本的情况下从一个叶层转移到另一个叶层。最后，我们将 TP10W 模拟的结果与点突变变体（TP10W-K12A18 和 TP10W-K19L）的结果进行了比较，以了解电荷分布对肽的影响。结果表明，这种保守突变会导致表面结合和跨膜状态的构象发生明显变化。本研究的结果将与实验观察到的 TP10W 对中性膜的活性进行讨论。
