Thermodynamic measurements of bilayer insertion of a single transmembrane helix chaperoned by fluorinated surfactants.
Thermodynamic measurements of bilayer insertion of a single transmembrane helix chaperoned by fluorinated surfactants.
复制标题
DOI：
10.1016/j.jmb.2011.12.037
复制
发表时间：
2012-02-24
影响因子：
5.6
通讯作者：
Ladokhin, Alexey S.
中科院分区：
文献类型：
--
作者：
Kyrychenko, Alexander;Rodnin, Mykola V.;Posokhov, Yevgen O.;Holt, Andrea;Pucci, Bernard;Killian, J. Antoinette;Ladokhin, Alexey S.
准确测定螺旋片段从水分子转移到跨膜构象的自由能，对于理解和预测膜蛋白的折叠和稳定性至关重要。直到最近，由于肽聚集在脂质双分子层外，对疏水跨膜肽插入自由能的直接热动力学声测量是不可能的。在这里，我们通过使用含氟表面活性剂来克服这个问题，这种表面活性剂能够防止聚集，但与洗涤剂不同的是，它本身不与双分子层相互作用。我们应用FCS方法研究了两种不同长度的染料标记的跨膜肽：WALP23和WALP27，表面活性剂在预先形成的POPC囊泡中的插入。将表面活性剂存在时测量的表观自由能值外推至零表面活性剂浓度时，插入WALP23和WALP27的自由能值分别为- 9.0±0.1和- 10.0±0.1 kcal/mol。圆二色性测量证实了肽在脂质双分子层、表面活性剂存在和有机溶剂的水混合物中的螺旋结构。从热力学和构象测量的结合我们得出结论，在连续螺旋构象的情况下，4-残基L-A-L-A段从水环境分配到膜的碳氢化合物核心具有每摩尔1千卡的有利自由能。我们的测量，结合两个独立的实验疏水性尺度的预测，表明螺旋骨架从水转移到脂质双分子层碳氢化合物核心的每残基成本是不利的，等于+2.13±0.17 kcal/mol。
Accurate determination of the free energy of transfer of a helical segment from aqueous into a transmembrane conformation is essential for understanding and predicting of the folding and stability of membrane proteins. Until recently, direct thermodynamically sound measurements of free energy of insertion of hydrophobic transmembrane peptides were impossible due to peptide aggregation outside the lipid bilayer. Here we overcome this problem by using fluorinated surfactants that are capable of preventing aggregation, but, unlike detergents, do not themselves interact with the bilayer. We have applied FCS methodology to study surfactant-chaperoned insertion into preformed POPC vesicles of the two well-studied dye-labeled transmembrane peptides of different lengths: WALP23 and WALP27. Extrapolation of the apparent free energy values measured in the presence of surfactants to a zero surfactant concentration yielded free energy values of −9.0±0.1 and −10.0±0.1 kcal/mole for insertion of WALP23 and WALP27, respectively. Circular dichroism measurements confirmed helical structure of peptides in lipid bilayer, in the presence of surfactants and in aqueous mixtures of organic solvents. From a combination of thermodynamic and conformational measurements we conclude that the partitioning of a 4-residue L-A-L-A segment in the context of a continuous helical conformation from aqueous environment into the hydrocarbon core of the membrane has a favorable free energy of one kcal per mole. Our measurements, combined with the predictions of two independent experimental hydrophobicity scales, indicate that the per-residue cost of transfer of the helical backbone from water to the hydrocarbon core of the lipid bilayer is unfavorable and equals +2.13±0.17 kcal/mole.
登录
查看更多内容
影响因子：
2.4
作者：
Fernandez-Vidal, Monica;White, Stephen H.;Ladokhin, Alexey S.
通讯作者：
Ladokhin, Alexey S.
DOI：
10.1007/s00249-009-0567-1
发表时间：
2010-03
影响因子：
2
作者：
Holt, Andrea;Killian, J. Antoinette
通讯作者：
Killian, J. Antoinette
影响因子：
2.9
作者：
Miller, CJ;Elliott, JL;Collier, RJ
通讯作者：
Collier, RJ
DOI：
10.1073/pnas.94.8.3668
发表时间：
1997-04-15
影响因子：
11.1
作者：
Hsu, YT;Wolter, KG;Youle, RJ
通讯作者：
Youle, RJ
影响因子：
5.6
作者：
Ladokhin, AS;White, SH
通讯作者：
White, SH