The effects of alpha-helical structure and cyanylated cysteine on each other.
The effects of alpha-helical structure and cyanylated cysteine on each other.
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DOI：
10.1021/jp101447r
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发表时间：
2010-04-15
影响因子：
3.3
通讯作者：
Londergan, Casey H.
中科院分区：
文献类型：
--
作者：
Edelstein, Lena;Stetz, Matthew A.;McMahon, Heather A.;Londergan, Casey H.
β-硫氰基丙氨酸或氰基化半胱氨酸是一种人工氨基酸，可以通过化学修饰在蛋白质中暴露于溶剂的半胱氨酸残基处引入。其易于翻译后合成意味着它可能在大型蛋白质系统中作为位点特异性结构和动力学的探针而得到广泛应用。该人工侧链的C-N伸缩振动提供了分离的红外发色团。为了测试这种侧链对局部二级结构的扰动作用及其对结构变化的敏感性，合成了三种在不同位点含有氰酰化半胱氨酸的模型水溶性丙氨酸重复螺旋的变体。氰酰化的半胱氨酸侧链被证明是不稳定的，但不完全破坏，折叠的肽的螺旋结构时，取代丙氨酸。此外，人工侧链的C N伸缩带宽对螺旋-卷曲结构转变敏感。这些模型系统的结果表明，氰酰化的半胱氨酸可以被放置到蛋白质序列与天然螺旋的倾向，而不破坏螺旋，并进一步的CN探针可能能够报告当地的螺旋形成事件，即使当它是水暴露在有序和无序的构象状态。这些结果表明，氰基化半胱氨酸可能是一个广泛有用的探针的结构形成事件的蛋白质在体外结构分布大。
β-Thiocyanatoalanine, or cyanylated cysteine, is an artificial amino acid that can be introduced at solvent-exposed cysteine residues in proteins via chemical modification. Its facile post-translational synthesis means that it may find broad use in large protein systems as a probe of site-specific structure and dynamics. The C≡N stretching vibration of this artificial side chain provides an isolated infrared chromophore. To test both the perturbative effect of this side chain on local secondary structure and its sensitivity to structural changes, three variants of a model water-soluble alanine-repeat helix were synthesized containing cyanylated cysteine at different sites. The cyanylated cysteine side chain is shown to destabilize, but not completely disrupt, the helical structure of the folded peptide when substituted for alanine. In addition, the C≡N stretching bandwidth of the artificial side chain is sensitive to the helix−coil structural transition. These model system results indicate that cyanylated cysteine can be placed into protein sequences with a native helical propensity without destroying the helix, and further that the CN probe may be able to report local helix formation events even when it is water-exposed in both the ordered and disordered conformational states. These results indicate that cyanylated cysteine could be a widely useful probe of structure-forming events in proteins with large in vitro structural distributions.
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