Refined NMR structure of α-sarcin by 15N-1H residual dipolar couplings
Refined NMR structure of α-sarcin by 15N-1H residual dipolar couplings
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DOI：
10.1007/s00249-005-0473-0
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发表时间：
2005-11-01
影响因子：
2
通讯作者：
Bruix, M
中科院分区：
文献类型：
--
作者：
García-Mayoral, MF;Pantoja-Uceda, D;Bruix, M
N-15-H-1残基偶极偶联（RDC）已被用作额外的限制以细化核糖毒素α-八叠球菌素的溶液结构。RDC值通过α-八叠球菌素在正十二烷基六（乙二醇）/己醇的二元混合物中的部分排列获得。共测量了131个RDC，并在基于核Over-hauser增强和扭转角约束的主要计算之后，在计算方案的最后步骤中引入了106个RDC。得到了一个81个构象异构体的同质家族。对应于20个最佳结构的叠加的所得平均成对均方根偏差对于主链为0.69 +/-0.12埃，对于所有重原子为1.29 +/-0.14埃。与α-八叠球菌素的非精细结构相比，来自精细结构的新结构特征包括新的氢键和更好的主链构象定义。特别是，跨越Gly 60至Lys 70的环段显示出单一构象，对应于在未精制结构中观察到的最多的构象异构体家族。从精细结构的分析和与同源蛋白限制曲蛋白的比较中得到的信息可以帮助建立关于α-八叠球菌素的进一步结构-功能关系，其可以合理地外推到核糖毒素家族的其他成员。
N-15-H-1 residual dipolar couplings (RDC) have been used as additional restraints to refine the solution structure of the ribotoxin alpha-sarcin. The RDC values were obtained by partial alignment of alpha-sarcin in the binary mixture of n-dodecyl hexa(ethylene glycol)/hexanol. A total of 131 RDCs were measured and 106 were introduced in the final steps of the calculation protocol following the main calculation based on nuclear Over-hauser enhancements and torsion angle restraints. A homogeneous family of 81 conformers was obtained. The resulting average pairwise root-mean-square deviation corresponding to the superposition of the 20 best structures is 0.69 +/- 0.12 angstrom for the backbone and 1.29 +/- 0.14 angstrom for all heavy atoms. The new structural features derived from the refined structure, compared with the non-refined structure of alpha-sarcin, consist of new hydrogen bonds and a better definition of the backbone conformation. In particular, the loop segment spanning Gly 60 to Lys 70 shows a single conformation, corresponding to the most populated family of conformers observed in the unrefined structure. The information derived from the analysis of the refined structure and the comparison with the homologous protein restrictocin could help in establishing further structure-function relationships concerning a-sarcin which can be reasonably extrapolated to other members of the ribotoxin family.