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环状排列对蛋白质瞬时部分解折叠的影响。

Effect of circular permutations on transient partial unfolding in proteins.

作者信息

Chen Chen, Yun Jung-Hun, Kim Jae-Hoon, Park Chiwook

机构信息

Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, Indiana, 47907.

Faculty of Biotechnology, College of Applied Life Science, SARI, Jeju National University, Jeju-Do, 690-756, Korea.

出版信息

Protein Sci. 2016 Aug;25(8):1483-91. doi: 10.1002/pro.2945. Epub 2016 May 24.

Abstract

Under native conditions, proteins can undergo transient partial unfolding, which may cause proteins to misfold or aggregate. A change in sequence connectivity by circular permutation may affect the energetics of transient partial unfolding in proteins without altering the three-dimensional structures. Using Escherichia coli dihydrofolate reductase (DHFR) as a model system, we investigated how circular permutation affects transient partial unfolding in proteins. We constructed three circular permutants, CP18, CP37, and CP87, with the new N-termini at residue 18, 37, and 87, respectively, and probed transient partial unfolding by native-state proteolysis. The new termini in CP18, CP37, and CP87 are within, near, and distal to the Met20 loop, which is known to be dynamic and also part of the region that undergoes transient unfolding in wild-type DHFR. The stabilities of both native and partially unfolded forms of CP18 are similar to those of wild-type DHFR, suggesting that the influence of introducing new termini in a dynamic region to the protein is minimal. CP37 has a significantly more accessible partially unfolded form than wild-type DHFR, demonstrating that introducing new termini near a dynamic region may promote transient partial unfolding. CP87 has significantly destabilized native and partially unfolded forms, confirming that modification of the folded region in a partially unfolded form destabilizes the partially unfolded form similar to the native form. Our findings provide valuable guidelines to control transient partial unfolding in designing circular permutants in proteins.

摘要

在天然条件下,蛋白质会经历短暂的部分解折叠,这可能导致蛋白质错误折叠或聚集。通过环形排列改变序列连接性可能会影响蛋白质中短暂部分解折叠的能量学,而不会改变其三维结构。以大肠杆菌二氢叶酸还原酶(DHFR)作为模型系统,我们研究了环形排列如何影响蛋白质中的短暂部分解折叠。我们构建了三个环形排列突变体,CP18、CP37和CP87,其新的N端分别位于第18、37和87位残基处,并通过天然状态下的蛋白酶解来探测短暂部分解折叠。CP18、CP37和CP87中的新末端分别位于Met20环内部、附近和远端,已知Met20环具有动态性,也是野生型DHFR中经历短暂解折叠区域的一部分。CP18的天然形式和部分解折叠形式的稳定性与野生型DHFR相似,这表明在动态区域引入新末端对蛋白质的影响最小。CP37具有比野生型DHFR明显更容易接近的部分解折叠形式,表明在动态区域附近引入新末端可能会促进短暂部分解折叠。CP87的天然形式和部分解折叠形式均显著不稳定,证实以部分解折叠形式对折叠区域进行修饰会使部分解折叠形式与天然形式一样不稳定。我们的研究结果为在设计蛋白质环形排列突变体时控制短暂部分解折叠提供了有价值的指导。

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