MyoD蛋白bHLH區塊片段系列衍生物光譜特性之研究

Spectroscopic study of the MyoD protein bHLH active fragment

盧耀翔(Yao-Shiang Lu)

指導教授 ： 錢偉鈞

朝陽科技大學/理工學院/應用化學系/碩士(2015年)

摘要

本實驗以MyoD蛋白質中HLH活性部位之13肽片段Peptide 3C之一級結構 H-Tyr-Ile-Glu-Gly-Leu-Gln-Ala-Leu-Leu-Arg-Asp-Gln-Cys-NH2為藍本探討序列縮減對胜肽構型之影響，藉以討論構型與此段胜肽抑制腫瘤細胞增生之活性關連。根據圓二色光譜及核磁共振光譜實驗結果顯示Peptide 3C在水溶液中主要呈現無序纏捲，但在N端逐次縮減時，C端胺基酸殘基β-構型特徵則逐漸明顯，而在Leu8 -Leu9可能存有迴路。結果顯示自碳端逐次縮減6個殘基對胜肽構型並無明顯之影響，此一結果顯示Peptide 3C之N端序列為影響構型之關鍵。由核磁共振DOSY光譜所測量之擴散係數結果顯示，自N端縮減之各胜肽的擴散係數隨分子量下降而增加，而自C端縮減至CtD2時隨著胜肽分子量減少而擴散係數值增加，但縮減至CtD3 (末端含有Leu5、Leu8、Leu9)時擴散係數值下降，而CtD4 (最末端為Leu9)無法溶解於水，顯示C端縮減之各胜肽受厭水性胺基酸之影響產生聚集(aggregate)之可能。結果顯示Peptide 3C之N端序列為影響構型之關鍵，此一構型特徵與其抑制細胞增生之關連將進一步探討。

關鍵字

核磁共振(NMR) ； 擴散係數

並列摘要

Peptide 3C is a trideca peptide derived from the HLH active site of MyoD protein. The primary structure is H-Tyr-Ile-Glu-Gly-Leu-Gln-Ala-Leu-Leu-Arg -Asp-Gln-Cys-NH2. The results of circular dichroism spectrum and nuclear magnetic spectroscopy show that in aqueous solution peptide 3C exists mainly as random coil in aqueous solution, with β-strand in N-terminal and a turn-like character at Leu8~Leu9. With the residue deletion from the C-terminal did not cause obvious change in conformation while the deletion from the N-terminal decreases the β- character in N-terminal fragment and induce formation of β-strand at the C-terminal at the same time. Base on the diffusion coefficients measured by DOSY, Ds for the N-terminal deletion derivatives increases with the decrease of molecular weight. This tendency did not appear for the C-terminal derivatives. The hydrophobic residues at C-terminal would cause the aggregation for the C-terminal derivatives. These observations show that the residues at the N-terminal of peptide 3C play the key factor in the conformation of the peptide while the aggregation caused by C-terminal deletion would hinder the biological function.

並列關鍵字

Peptide 3C

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