Helix formation and the unfolded state of a 52-residue helical protein
Helix formation and the unfolded state of a 52-residue helical protein
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DOI：
10.1110/ps.03383004
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发表时间：
2004-01-01
期刊：
影响因子：
8
通讯作者：
Lu, M
中科院分区：
文献类型：
--
作者：
Cao, W;Bracken, C;Lu, M
人们发现生物过程中越来越多的蛋白质在正常溶液条件下分离时会展开。我们使用核磁共振波谱来表征 52 个残基富含丙氨酸的蛋白质 (Ala-14) 在 -50°C 至 40°C 温度下的未折叠和部分折叠状态的结构和动态特性。在 40°C 时，Ala-14 中的丙氨酸残基采用 phi 和 psi 角度，与聚脯氨酸 11 构象的重要整体群体一致。对蛋白质弛豫率的分析表明，一系列残基 Gln 35-Ala 36-Ala 37-Lys 38-Asp 39-Asp 40-Ala 41-Ala 42 在 -5°C 和 40°C 下均表现出慢运动动力学。温度依赖性化学位移变化表明该区域是螺旋起始的位点。剩余的 N 端残基随着从成核位点延伸而变得越来越动态。 C 末端保持动态并且随温度变化较小，表明它相对非结构化。 Ala-14 提供了未折叠状态以及在没有三级接触的情况下螺旋成核和传播过程的高分辨率图像，这些信息与蛋白质折叠的早期事件有关。
A growing class of proteins in biological processes has been found to be unfolded on isolation under normal solution conditions. We have used NMR spectroscopy to characterize the structural and dynamic properties of the unfolded and partially folded states of a 52-residue alanine-rich protein (Ala-14) at temperatures from -50degreesC to 40degreesC. At 40degreesC, alanine residues in Ala-14 adopt phi and psi angles, consistent with a significant ensemble population of polyproline 11 conformation. Analysis of relaxation rates in the protein reveals that a series of residues, Gln 35-Ala 36-Ala 37-Lys 38-Asp 39-Asp 40-Ala 41-Ala 42, displays slow motional dynamics at both -5degreesC and 40degreesC. Temperature-dependent chemical shift changes indicate that this region is the site of helix initiation. The remaining N-terminal residues become increasingly dynamic as they extend from the nucleation site. The C terminus remains dynamic and changes less with temperature, indicating it is relatively unstructured. Ala-14 provides a high-resolution portrait of the unfolded state and the process of helix nucleation and propagation in the absence of tertiary contacts, information that bears on early events in protein folding.