Mechanism and Kinetics of Peptide Partitioning into Membranes from All-Atom Simulations of Thermostable Peptides
Mechanism and Kinetics of Peptide Partitioning into Membranes from All-Atom Simulations of Thermostable Peptides
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DOI：
10.1021/ja909347x
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发表时间：
2010-03-17
影响因子：
15
通讯作者：
Ulmschneider, Jakob P.
中科院分区：
文献类型：
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作者：
Ulmschneider, Martin B.;Doux, Jacques P. F.;Ulmschneider, Jakob P.
跨膜多肽片段的分配特性直接决定了膜蛋白的折叠、稳定性和功能，对其的理解对膜活性肽的合理设计至关重要。然而，直接测定TM肽的水到双层转移已被证明是困难的。实验上，足够疏水的肽倾向于聚集，而生理温度下的原子计算机模拟尚不能达到捕获分配所需的长时间尺度。人们避免了升高温度来加速其动力学，因为这被认为会导致快速变性。然而，我们在这里表明，模型TM肽（WALP）具有异常的耐热性。圆二色性实验表明，即使在90摄氏度的温度下，肽仍然插入到脂质双分子层中，并且是完全螺旋状的。在这些温度下，采样速度类似于50-500倍，足以直接模拟原子分辨率下的自发分配。观察到一个折叠的插入路径，符合三阶段划分理论。高温模拟集成进一步允许直接计算插入动力学，发现所有系统都是一阶的。插入屏障为δ H-in（双匕首），一般疏水肽为15 kcal/mol，色氨酸侧的WALP肽为23 kcal/mol。室温下相应的插入时间范围为8.5 μ s ~ 163 ms。实验验证的热稳定系统的高温模拟为系统探索肽分配特性提供了新的途径。
Partitioning properties of transmembrane (TM) polypeptide segments directly determine membrane protein folding, stability, and function, and their understanding is vital for rational design of membrane active peptides. However, direct determination of water-to-bilayer transfer of TM peptides has proved difficult. Experimentally, sufficiently hydrophobic peptides tend to aggregate, while atomistic computer simulations at physiological temperatures cannot yet reach the long time scales required to capture partitioning. Elevating temperatures to accelerate the dynamics has been avoided, as this was thought to lead to rapid denaturing. However, we show here that model TM peptides (WALP) are exceptionally thermostable. Circular dichroism experiments reveal that the peptides remain inserted into the lipid bilayer and are fully helical, even at 90 degrees C. At these temperatures, sampling is similar to 50-500 times faster, sufficient to directly simulate spontaneous partitioning at atomic resolution. A folded insertion pathway is observed, consistent with three-stage partitioning theory. Elevated temperature simulation ensembles further allow the direct calculation of the insertion kinetics, which is found to be first-order for all systems. Insertion barriers are Delta H-in(double dagger) = 15 kcal/mol for a general hydrophobic peptide and similar to 23 kcal/mol for the tryptophan-flanked WALP peptides. The corresponding insertion times at room temperature range from 8.5 mu s to 163 ms. High-temperature simulations of experimentally validated thermostable systems suggest a new avenue for systematic exploration of peptide partitioning properties.