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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Structural characterization of an engineered tandem repeat contrasts the importance of context and sequence in protein folding
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Structural characterization of an engineered tandem repeat contrasts the importance of context and sequence in protein folding

机译：工程串联重复序列的结构表征对比了蛋白质折叠中背景和序列的重要性

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摘要

To test a different approach to understand- ing the relationship between the sequence of part of a protein and its conformation in the overall folded structure, the amino acid sequence corresponding to an #alpha#-helix of T4 lysozyme was duplicated in tandem. The presence of such a sequence repeat provides the protein with "choices" during folding. The mu- tant Protein folds with almost wild-type stability, is active, and crystallizes in two different space groups, one isomorphous with wild type and the other with two molecules in the asymmetric unit. The fold of the mutant is essentially the same in all cases, showing that the inserted segment has a well- defined structure. More than half of the inserted residues are themselves helical and extend the helix present in the wild- type protein. Participation of additional duplicated residues in this helix would have required major disruption of the parent structure. The results clearly show that the residues within the duplicated sequence tend to maintain a helical conformation even though the packing interactions with the remainder of the protein are different from those of the original helix. It supports the hypothesis that the structures of individual #alpha#-helices are determined predominantly by the nature of the amino acids within the helix, rather than the structural environment Provided by the rest of the protein.
机译：为了测试一种不同的方法来理解蛋白质的一部分序列及其在整体折叠结构中的构象之间的关系，将与T4溶菌酶的＃alpha＃-螺旋对应的氨基酸序列串联复制。此类重复序列的存在为蛋白质在折叠过程中提供了“选择”。突变蛋白折叠后几乎具有野生型稳定性，具有活性，并在两个不同的空间群中结晶，一个在野生型中同构，另一个在不对称单元中带有两个分子。在所有情况下，突变体的折叠倍数基本相同，表明插入的片段具有良好定义的结构。一半以上的插入残基本身是螺旋状的，并延伸了野生型蛋白质中存在的螺旋。额外的重复残基参与该螺旋结构将需要对母体结构的重大破坏。结果清楚地表明，即使与蛋白质其余部分的堆积相互作用不同于原始螺旋的堆积相互作用，重复序列内的残基也倾向于保持螺旋构象。它支持以下假设：单个＃α＃螺旋的结构主要由螺旋中氨基酸的性质决定，而不是由其余蛋白质提供的结构环境决定。

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