Structural stability of proteins in aqueous and nonpolar environments.
Structural stability of proteins in aqueous and nonpolar environments.
复制标题
蛋白质在水性和非极性环境中的结构稳定性。
DOI：
10.1063/1.4755755
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
M. Kinoshita
中科院分区：
文献类型：
--
作者：
S. Yasuda;Hiraku Oshima;M. Kinoshita
在生理条件下，蛋白质在水溶液中以α-螺旋和β-折叠的形式折叠成其天然结构。这些二级结构的相对含量因蛋白质而异。然而，这种结构变异性在非水环境中不表现出来。例如，有一种强烈的趋势，即酒精诱导蛋白质形成α-螺旋，并且脂质双层内的许多膜蛋白由α-螺旋组成。本文基于统计热力学理论，利用最近发展的自由能函数F =（Λ - TS）scink（k（B）T（0））= Λ scink（k（B）T（0））- S scink（B）（T（0）= 298 K，绝对温度T设为T（0）），研究了蛋白质在水溶液和非极性环境中的结构稳定性.Λ scink（k（B）T（0））和S scink（B）分别是能量分量和熵分量，并且k（B）是玻尔兹曼常数。正量-S的值越小，表示主链和侧链堆积的效率越高，这是由溶剂分子或CH（2）、CH（3）和CH基团的平移位移引起的熵效应促进的，这些基团构成脂质分子的非极性链。至于Λ，在水溶液中，蛋白质向更紧凑结构的转变伴随着蛋白质-溶剂氢键的断裂：随着没有蛋白质分子内氢键的供体和受体数量的增加，Λ变得更高。在非极性溶剂中，较低的Λ仅仅意味着形成更多的分子内氢键。我们发现以下情况。α-螺旋和β-折叠相对于-S以及Λ是有利的，并且尽可能多地形成。在水溶液中，溶剂熵效应对结构稳定性的影响很大，侧链的紧密堆积起着决定性的作用，而α-螺旋和β-折叠的含量则需要适当的调节，在非极性溶剂中，溶剂熵效应要比在水溶液中弱得多。Λ是决定性的，α-螺旋比β-折叠在Λ方面更稳定，这发展了α-螺旋被排他地选择的趋势。对于膜蛋白，α-螺旋由于相同的原因被稳定为基本结构单元，但它们的排列是通过上述熵效应进行的。
A protein folds into its native structure with the α-helix and∕or β-sheet in aqueous solution under the physiological condition. The relative content of these secondary structures largely varies from protein to protein. However, such structural variability is not exhibited in nonaqueous environment. For example, there is a strong trend that alcohol induces a protein to form α-helices, and many of the membrane proteins within the lipid bilayer consists of α-helices. Here we investigate the structural stability of proteins in aqueous and nonpolar environments using our recently developed free-energy function F = (Λ - TS)∕(k(B)T(0)) = Λ∕(k(B)T(0)) - S∕k(B) (T(0) = 298 K and the absolute temperature T is set at T(0)) which is based on statistical thermodynamics. Λ∕(k(B)T(0)) and S∕k(B) are the energetic and entropic components, respectively, and k(B) is Boltzmann's constant. A smaller value of the positive quantity, -S, represents higher efficiency of the backbone and side-chain packing promoted by the entropic effect arising from the translational displacement of solvent molecules or the CH(2), CH(3), and CH groups which constitute nonpolar chains of lipid molecules. As for Λ, in aqueous solution, a transition to a more compact structure of a protein accompanies the break of protein-solvent hydrogen bonds: As the number of donors and acceptors buried without protein intramolecular hydrogen bonding increases, Λ becomes higher. In nonpolar solvent, lower Λ simply implies more intramolecular hydrogen bonds formed. We find the following. The α-helix and β-sheet are advantageous with respect to -S as well as Λ and to be formed as much as possible. In aqueous solution, the solvent-entropy effect on the structural stability is so strong that the close packing of side chains is dominantly important, and the α-helix and β-sheet contents are judiciously adjusted to accomplish it. In nonpolar solvent, the solvent-entropy effect is substantially weaker than in aqueous solution. Λ is crucial and the α-helix is more stable than the β-sheet in terms of Λ, which develops a tendency that α-helices are exclusively chosen. For a membrane protein, α-helices are stabilized as fundamental structural units for the same reason, but their arrangement is performed through the entropic effect mentioned above.
影响因子：
5.6
作者：
S. Sneddon;D. Tobias;C. Brooks
通讯作者：
S. Sneddon;D. Tobias;C. Brooks
影响因子：
2.9
作者：
Feig, M;Karanicolas, J;Brooks, CL
通讯作者：
Brooks, CL