Main-chain dynamics of a partially folded protein: 15N NMR relaxation measurements of hen egg white lysozyme denatured in trifluoroethanol.
Main-chain dynamics of a partially folded protein: 15N NMR relaxation measurements of hen egg white lysozyme denatured in trifluoroethanol.
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DOI：
10.1006/jmbi.1996.0193
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发表时间：
1996-04
影响因子：
5.6
通讯作者：
Matthias Buck;H. Schwalbe;C. M. Dobson
中科院分区：
文献类型：
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作者：
Matthias Buck;H. Schwalbe;C. M. Dobson
15 N NMR弛豫测量已被用来研究的动态行为的母鸡溶菌酶的主链在部分折叠状态下，形成在70%（v/v）三氟乙醇（TFE）/30%的水混合物在37 ℃和pH 2。这种状态的特点是在没有广泛的三级相互作用的螺旋二级结构。核磁共振弛豫数据进行了解释映射的谱密度函数和推导的节段以及全球秩序参数。结果表明，溶菌酶在TFE中的动态，至少对于绝大多数的残留物，可以充分描述的内部运动叠加在所有的整体各向同性翻滚的分子。虽然动态行为显示沿沿着的多肽链的实质性变化，它与其他NMR参数确定的TFE状态的构象偏好。作为持久螺旋结构的一部分的多肽链的片段在其运动中受到高度限制（S2 > 0.8，有效内部相关时间τ（e）< 200 ps），但也发现在毫秒时间尺度上经历构象交换。在较不持久的螺旋结构中稳定的区域具有更大的柔性（0.6 < S2 < 0.8，200 ps < tau（e）< 1 ns），而缺乏确定的构象偏好的那些区域是高度柔性的（S2 < 0.6，tau（e）约1 ns）。主链的动态行为被发现与多肽链的其他局部特征相关，包括疏水性和二硫桥的位置。尽管没有广泛的三级相互作用，优先稳定的原生二级结构的TFE结果在主链动力学的模式，这是类似的原生状态。
15N NMR relaxation measurements have been used to study the dynamic behaviour of the main-chain of hen lysozyme in a partially folded state, formed in a 70% (v/v) trifluoroethanol (TFE)/30% water mixture at 37 degrees C and pH 2. This state is characterised by helical secondary structure in the absence of extensive tertiary interactions. The NMR relaxation data were interpreted by mapping of spectral density functions and by derivation of segmental as well as global order parameters. The results imply that the dynamics of lysozyme in TFE can, at least for the great majority of residues, be adequately described by internal motions which are superimposed on all overall isotropic tumbling of the molecule. Although the dynamic behaviour shows substantial variations along the polypeptide chain, it correlates well with the conformational preferences identified in the TFE state by other NMR parameters. Segments of the polypeptide chain which are part of persistent helical structures are highly restricted in their motion (S2 > 0.8 , with effective internal correlation times tau(e) < 200 ps) but are also found to experience conformational exchange on a millisecond timescale. Regions which are stabilised in less persistent helical structure possess greater flexibility (0.6 < S2 < 0.8, 200 ps < tau(e) < 1 ns) and those which lack defined conformational preferences are highly flexible (S2 < 0.6, tau(e) approximately 1 ns). The dynamic behaviour of the main-chain was found to be correlated with other local features of the polypeptide chain, including hydrophobicity and the position of the disulphide bridges. Despite the absence of extensive tertiary interactions, preferential stabilisation of native-like secondary structure by TFE results in a pattern of main-chain dynamics which is similar to that of the native state.