Accretion of structure in staphylococcal nuclease: An N-15 NMR relaxation study
Accretion of structure in staphylococcal nuclease: An N-15 NMR relaxation study
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DOI：
10.1006/jmbi.1996.0422
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发表时间：
1996-07-26
影响因子：
5.6
通讯作者：
Blommers, MJJ
中科院分区：
文献类型：
--
作者：
Alexandrescu, AT;Jahnke, W;Blommers, MJJ
将N-15主链动力学以四种形式的葡萄球菌核酸酶进行比较，其稳定性不同：（1）SN-T，蛋白质的三元络合物Ca2+和抑制剂胸苷3'，5'-双磷酸； （2）SN，在没有添加配体的情况下蛋白质； （3）SN-OB，折叠的片段，对应于“ ob-fold”子域； （4）Delta 131 Delta，一个变性的131个残留片段。 SN-T在纳秒时间尺度上几乎没有内部运动。在SN中，观察到五链β片的前三个线的柔韧性适度提高，以及在链4和5之间的循环。 4和;，在纳秒时间尺度上非常灵活。尽管SN-OB和SN的Beta表在纳秒时间尺度上具有可比的动力学，但SN-OB中的Beta片在330（+/- 170）微秒较慢的时间尺度上体验了额外的运动。我们将后者归因于主要折叠（大于或等于98％）和次要展开（大于或等于2％）构象之间的互连。在Delta 131 Delta中，Beta表体验的前三链在毫秒时尺度上平均，其余大多数多肽链在纳米秒时尺寸都非常灵活。当考虑所有四种形式的核酸酶时，随着折叠状态的稳定性降低，具有较大振幅内部运动（低阶参数）的残基的比例增加。具有低阶参数的残基聚类到链的不同区域，并具有H-α化学位移，并且（3）J（Hn-H-Halpha）耦合常数倾向于“随机线圈”值。相反，统一高阶参数的趋势表明结构的巩固随着变性的稳定性的增加。 （c）1996 Academic Press Limited
N-15 main-chain dynamics are compared in four forms of staphylococcal nuclease with different stabilities to unfolding: (1) SN-T, the ternary complex of the protein, Ca2+ and the inhibitor thymidine 3', 5'-bisphosphate; (2) SN, the protein in the absence of added ligands; (3) SN-OB, a folded fragment that corresponds to an ''OB-fold'' subdomain; (4) Delta 131 Delta, a denatured 131-residue fragment. SN-T exhibits very little internal motion on the nanosecond timescale. In SN, a moderate increase in flexibility is observed for the first three strands of the five-stranded beta-sheet, and for a loop between strands 4 and 5. In SN-OB, the loops between strands 3 and 4, and between strands 4 and;, are extremely flexible on the nanosecond timescale. While the beta-sheets of SN-OB and SN have comparable dynamics on the nanosecond timescale, the beta-sheet in SN-OB experiences additional motion on a slower timescale of 330(+/-170) microseconds. We attribute the latter to interconversion between a major folded (greater than or equal to 98%) and a minor unfolded (greater than or equal to 2%) conformation. In Delta 131 Delta, the first three strands of beta-sheet experience conformational averaging on the millisecond timescale, Most of the remainder of the polypeptide chain is highly flexible on the nanosecond timescale. When all four forms of nuclease are considered, there is an increase in the proportion of residues with large amplitude internal motions (low order parameters) as the stability of the folded state is decreased. Residues with low order parameters cluster to distinct regions of the chain, and have H-alpha chemical shifts and (3)J(HN-H alpha) coupling constants that tend towards ''random coil'' values. Conversely, a trend towards uniformly high order parameters suggests a consolidation of structure with increasing stability to denaturation. (C) 1996 Academic Press Limited