蛋白質穩定性與聚集傾向間關聯性之探討：以in silico方法研究Retinoschisin突變體為研究案例

The Dilemma in Protein Stability and Aggregation Propensity: A Case Study of the Retinoschisin Mutants by in silico Methods

吳宛儒(Wan-Ru Wu)

指導教授 ： 劉宣良

國立臺北科技大學/工程學院/工程科技研究所/博士(2011年)

摘要

先天性X染色體串聯視網膜裂損症(XLRS)是一種由分泌蛋白retinoschisin（RS1）突變所引起的視網膜疾病。大多數的致病突變在discoidin區域具單點突變，¬而半胱氨酸殘基之突變往往與較嚴重的XLRS病例相關。過去的研究指出，涉及在天然dicoidin區域中分子內雙硫鍵形成的半胱氨酸有關之兩種突變C110Y及C219G，會導致不同的聚集狀態蛋白質物種之產生。而且，過去的研究亦發現，在C110Y及C219G兩種突變中，產生聚集之傾向與由折疊自由能變化所計算而得之蛋白質穩定性間，並無關聯性；此點似乎與一般之認知不同。
透過同源模擬、生物資訊預測、分子動力學及對接模擬等工具，我們嘗試瞭解突變對RS1 discoidin區域結構的影響，並探討文獻中所發現結構穩定性及聚集傾向間之差異與此些影響間之關係。我們的結果顯示，C110Y 突變種擁有誘導不定形或非晶形聚集體生成之適當需求，例如，C110Y 突變種經由(1)形成將突變體鎖定之共價雙硫鍵及(2)將S1迴圈以在非晶形及纖維化聚集體中觀察到的

關鍵字

先天性X染色體串聯視網膜裂損症 ； retinoschisin蛋白 ； 同源模擬 ； 分子動力學模擬 ； 分子對接模擬 ； 蛋白質不穩定性 ； 蛋白質聚集傾向

並列摘要

The juvenile X-linked retinoschisis (XLRS) is a retinal disease caused by mutations in the secretory protein, retinoschisin (RS1). Majority of the disease causing mutations consist of single point mutations on the discoidin domain with cysteine mutations being related to some of the more severe cases of XLRS. Previous studies have indicated that two mutations (C110Y and C219G), which involve cysteines that form intramolecular disulfide bonds in the native discoidin domain, resulted in different oligomerization states of the proteins and did not correlate with the degree of protein stability as calculated by change in folding free energy. Through homology modeling, bioinformatics predictions, molecular dynamics (MD) and docking simulations, we attempt to understand what effects the mutations have on the structure of the RS1 discoidin domain in relevance to the discrepancy found between structural stability and aggregation propensity. Our results show that C110Y mutant possesses the proper requirement for initiation of amorphous aggregates, such as the potential for establishing stable platforms through the formation of covalent disulfide bond locking mutants together and stacking of S1 loops in anti-parallel fashion reminiscent of cross-

並列關鍵字

Juvenile X-linked retinoschisis (XLRS) ； retinoschisin (RS1) ； homology modeling ； molecular dynamics (MD) simulations ； molecular docking simulations ； protein instability ； aggregation propensity

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