Role of the Disulfide Bond in Prion Protein Amyloid Formation: A Thermodynamic and Kinetic Analysis
Role of the Disulfide Bond in Prion Protein Amyloid Formation: A Thermodynamic and Kinetic Analysis
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DOI：
10.1016/j.bpj.2017.12.031
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发表时间：
2018-02-27
影响因子：
3.4
通讯作者：
Honda, Ryo
中科院分区：
文献类型：
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作者：
Honda, Ryo
朊病毒疾病与朊病毒蛋白 (PrP) 结构转变为富含 β 折叠的聚集体 PrPSc 相关。先前的研究表明，连接 PrP C179 和 C214 的二硫键的还原在体外产生了富含淀粉样蛋白的聚集体。为了深入了解还原诱导的聚集，在这里，我通过检查 1) 天然 (N) 和聚集状态相对于未折叠 (U) 状态的平衡稳定性，2) 分隔 U 和聚集状态的过渡屏障，以及 3) 淀粉样蛋白错误折叠聚集体的最终结构，描述了二硫键还原如何调节 PrP 的蛋白质折叠/错误折叠景观。动力学和热力学实验表明，二硫键还原使 N 态和聚集态的平衡稳定性降低了大约 3 kcal/mol，而不会改变淀粉样蛋白聚集结构（至少在二级结构水平上）或聚集的过渡势垒。因此，二硫键还原通过熵稳定无序状态（包括 U 和聚集的过渡状态）来调节蛋白质折叠/错误折叠景观。这也表明N态的平衡稳定性，而不是聚集的转变势垒，是决定还原诱导PrP聚集的主导因素。
Prion diseases are associated with the structural conversion of prion protein (PrP) to a beta-sheet-rich aggregate, PrPSc. Previous studies have indicated that a reduction of the disulfide bond linking C179 and C214 of PrP yields an amyloidlike beta-rich aggregate in vitro. To gain mechanistic insights into the reduction-induced aggregation, here I characterized how disulfide bond reduction modulates the protein folding/misfolding landscape of PrP, by examining 1) the equilibrium stabilities of the native (N) and aggregated states relative to the unfolded (U) state, 2) the transition barrier separating the U and aggregated states, and 3) the final structure of amyloidlike misfolded aggregates. Kinetic and thermodynamic experiments revealed that disulfide bond reduction decreases the equilibrium stabilities of both the N and aggregated states by similar to 3 kcal/mol, without changing either the amyloidlike aggregate structure, at least at the secondary structural level, or the transition barrier of aggregation. Therefore, disulfide bond reduction modulates the protein folding/misfolding landscape by entropically stabilizing disordered states, including the U and transition state of aggregation. This also indicates that the equilibrium stability of the N state, but not the transition barrier of aggregation, is the dominant factor determining the reduction-induced aggregation of PrP.