Application of the augmented theory of alpha-helix-to-random-coil transitions of two-chain, coiled coils to extant data on synthetic, tropomyosin-analog peptides.
Application of the augmented theory of alpha-helix-to-random-coil transitions of two-chain, coiled coils to extant data on synthetic, tropomyosin-analog peptides.
复制标题
将双链卷曲螺旋的α螺旋到随机螺旋转变的增强理论应用于合成原肌球蛋白类似肽的现有数据。
DOI：
10.1002/bip.360270107
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发表时间：
1988
期刊：
影响因子：
2.9
通讯作者：
Skolnick,J
中科院分区：
文献类型：
--
作者：
Holtzer,A;Skolnick,J
双链卷曲螺旋中螺旋到随机卷曲转变的统计力学理论应用于两种合成卷曲螺旋多肽的现有数据。这些肽具有一级结构 K(LEALEGK)n，其中 n= 4, 5。这种重复的七肽序列模拟了 284 个残基的原肌球蛋白分子（典型的卷曲螺旋蛋白）的疏水性、酸性和碱性残基特征的模式。单链的理论计算表明，此类模型肽不能直接与原肌球蛋白等蛋白质进行比较，因为链长（29 和 36 个残基 vs 284）和链内相互作用存在差异，后者是由蛋白质和模型之间的氨基酸组成和序列差异引起的。该理论应用于两种合成肽的现有数据提供了半定量拟合，并导致对模型肽中螺旋间相互作用的评估。获得的值 ∼ 2000 cal·（转角对的摩尔数）–1，比原肌球蛋白获得的值大四到五倍。这可能是由于合成物的结构具有更大的规律性以及疏水界面中仅存在亮氨酸。这里采用的理论坚持认为，合成中这种强大的螺旋间相互作用是这种短链在中低温下如此高度螺旋的主要原因。事实上，理论预测，具有与这些合成物同源序列的原肌球蛋白长度的链在水溶液中可达到的整个温度范围内将是完全热稳定的。理论还预测浓度对 29 和 36 残基合成聚合物的影响比预测或观察到的原肌球蛋白的影响要显着得多，并且还预测 pH 降低对热曲线的显着稳定作用。关于最后两点，目前还没有足够的数据来检验该理论。
The statistical mechanical theory for the helix‐to‐random‐coil transition in two‐chain coiled coils is applied to extant data for two synthetic coiled‐coil polypeptides. These peptides have the primary structure K(LEALEGK)n, in whichn= 4, 5. This repeating heptet sequence mimics the pattern of hydrophobic, acidic, and basic residues characteristic of the 284‐residue tropomyosin molecule, the prototypical coiled‐coil protein. Theoretical calculations for single chains show that such model peptides cannot be directly compared to proteins like tropomyosin because of differences in chain length (29 and 36 residues vs 284) and in intrachain interactions, the latter caused by the differences in amino acid composition and seqeunce between protein and model. Application of the theory to extant data on the two synthetic peptides provides a semiquantitative fit and results in an assessment of the interhelix interaction in the model peptides. The value obtained, ∼ 2000 cal · (mol of turn pairs)–1, is four to five times larger than has been obtained for tropomyosin. This probably is a result of greater regularity in the structure of the synthetics and of the exclusive presence of leucine in the hydrophobic interface. The theory employed here insists that this powerful interhelix interaction in the synthetic is the principal reason that such short chains can be so highly helical at moderate and low temperatures. Theory predicts, indeed, that a tropomyosin‐length chain with a sequence homologous to these synthetics would be completely thermally stable in the entire temperature range accessible in aqueous solutions. Theory also predicts a much more pronounced effect of concentration on the 29‐ and 36‐residue synthetic polymers than is predicted or observed in the case of tropomyosin, and it also predicts a pronounced stabilizing effect of pH‐reduction on the thermal curves. On the last two points, sufficient data are not yet available with which to test the theory.