請用此 Handle URI 來引用此文件:
http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/53826
標題: | 絲胺酸糖化對二級結構穩定性的影響及側鏈長度對離子對作用力的影響 Effect of Serine Glycosylation on Secondary Structure Stability and Effect of Side Chain Length on Ion Pairing Interaction of β-Hairpin Structure |
作者: | Tong Wai Wng 黃東偉 |
指導教授: | 陳平(Richard P. Cheng) |
關鍵字: | 胺基酸,離子作用力,後轉譯修飾, amino acids,ion pairing interaction,post-translational modification, |
出版年 : | 2015 |
學位: | 碩士 |
摘要: | 蛋白質的後轉譯修飾使蛋白質更加豐富和複雜。生物透過後轉譯修飾精密調控生物過程。蛋白質醣化是其中一種常見的後轉譯修飾,醣化的蛋白質參與生物體內的訊息傳導及細胞表面的辨認都被大幅報導。醣化對於生物體的功能和結構的影響已有不少研究。自然界中的醣化種類相當多,我們則主要集中在絲胺酸被beta-GlcNAc及-alpha-GalNAc這兩種常見的O-linked醣化作研究。透過小型的胜肽系統,我們對alpha螺旋及beta髮夾在醣化後的穩定性作出研究。我們的研究中發現絲胺酸被alpha-GalNAc修飾後,可以促進alpha螺旋形成的程度,在C端卻使螺旋程度減少。然而在beta髮夾中,被alpha-GalNAc修飾後的絲胺酸使beta髮夾穩定性下降,我們得出結論,被alpha-GalNAc修飾後的絲胺酸使多肽比較傾向形成螺旋。被beta-GlcNAc修飾後的絲胺酸對於beta髮夾的穩定性並沒有影響,然而卻會使多肽傾向形成alpha螺旋。帶相反電荷的離子對常被發現存在於反平行的beta折板中,而且是直接位於兩鏈之間;這意味著離子作用力對於beta髮夾的二級結構有著重要的影響。因此我們利用一個傾向形成beta髮夾的胜肽系統,研究在非氫鍵正對向位置上,不同長度的離子對對於beta髮夾穩定程度的影響。我們以glutamate及lysine衍生物做研究對象。負電荷在N端,正電荷在C端的組合已被研究過了。Serrano研究團隊發現,在交換離子對的位置後,對beta髮夾的穩定性有額外的穩固。當正電荷在N端,負電荷在C端的組合可以增加beta髮夾的折疊程度,所以我們利用相同的系統,研究正負電荷交換後對beta髮夾的穩定性的影響。文獻指出當正負電荷都是最短及最長組合時,折疊的程度最好;但當交換正負電荷位置時,正負電荷最短組合仍然是最穩定的,而最長組合卻失去穩定性。除此之外,我們也發現所有Aad(最長負電電荷)的組合都傾向不形成beta髮夾 Post-translational modifications (PTMs) increase the function and complexity of proteins. It provides a method to regulate a protein under different situations. Glycosylation is one kind of PTM. It is related to signal transduction and cell recognition. The functional and the structural effect of glycosylation have been studied. There are various types of glycosylation in nature. We focused on modifications of beta-GlcNAc and alpha-GalNAc, the two most abundant O-linked glycosylations. Both of these modifications occur on Ser or Thr. We developed an alpha-helical system to study the helix content and beta-hairpin system to study the beta-sheet stability.We discovered alpha-GalNAc glycosylation of Ser at the center of peptide increased the helicity,but the helicity decreased when Ser-alpha-GalNAc was introduced at the C-terminus.beta-GlcNAc glycosylation of Ser decreased the helicity at the N-terminus, C-terminus and the center of the peptide. The Ser beta-GlcNAc glycosylation in a hairpin did not affect beta-sheet stability, but Ser alpha-GalNAc glycosylationin the hairpin destabilized the hairpin.Charge interactions play important roles in protein folding. Various diseases related to aggregation of poly-beta-strands. Charge residue pairs are frequently found in lateral positions of an anti-parallel beta-sheet, which means there may be significant charge interactions. Asp, Glu, Lys and Arg are naturally existing amino acid residues. Only specific side chain lengths(methylene numbers) exist in nature. Why did nature choose these specific side chain lengths for these charged residues is an interesting question. We have developed a beta-hairpin system, which can allow us to measure the stability effects of individual charged residue and interactions. Negatively charged residues incorporated at the N-terminus guest site and positively charged residues incorporated at the C-terminus with lateral interactions have been previously studied by the Cheng group. Other studies have shown that swapping the position of the residues in the ion pair at the guest sites increased the stability of a beta-hairpin. Therefore we studied the effect of lateral ion pair interactions.Previous studies showed that the shortest and longest side chain ion pair have more stabilizing interaction energy. Swapping the position of the residues in the ion pairs gave similar results for the shortest side chain ion pair. However, the stabilization energy of Aad containing peptides was attenuated. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/53826 |
全文授權: | 有償授權 |
顯示於系所單位: | 化學系 |
文件中的檔案:
檔案 | 大小 | 格式 | |
---|---|---|---|
ntu-104-1.pdf 目前未授權公開取用 | 9.1 MB | Adobe PDF |
系統中的文件,除了特別指名其著作權條款之外,均受到著作權保護,並且保留所有的權利。