標題: 以螢光共振能量轉移揭示蛋白質PGB1分子內摺疊機制
The Folding Mechanism of Protein G B1 Domain Revealed by Fluorescence Resonance Energy Transfer
作者: 鍾偉賢
張家靖
生物科技學系
關鍵字: 蛋白質摺疊;螢光共振能量轉移;螢光焠滅;Protein G B1 Domain;Protein Folding;FRET;Fluorescence Quenching
公開日期: 2010
摘要: 蛋白質如何摺疊成特殊的結構,為目前學界不斷探討的重點。為了要能夠理解蛋白質摺疊機制,研究單功能區蛋白質(single-domain protein)變成了一個很重要的指標。本研究中,我們以Protein G B1 Domain(PGB1)作為研究之標的蛋白質,利用本實驗室所開發之蛋白質摺疊方法,Over-critical Folding Process,將PGB1由未摺疊態摺疊至自然態並觀察摺疊中間的結構變化。PGB1是一個小型蛋白質只有56個胺基酸,是Protein G的IgG-binding domain。藉由觀察PGB1自身的Trp43螢光光譜和acrylamide焠熄光譜,可發現PGB1之摺疊是一個二狀態反應(two-state reaction)的摺疊過程々而以動態光散射(dynamic light scattering)觀察分子大小的變化認為PGB1摺疊過程應具有另一個中間態存在。藉由螢光共振能量轉移(Fluorescence Resonance Energy Transfer,FRET)分析各主要二級結構之間在摺疊過程中的變化,發現PGB1的β-hairpin 2與α-helix在摺疊初期就已互相靠近,但其β-hairpin 1顯然較前者晚形成々綜合以上結果顯示蛋白質PGB1的摺疊是一個多狀態反應(multi-state reaction)。本研究藉由FRET方法為PGB1摺疊研究開啟新的一頁。
―How does a protein fold?‖ This has been questioned for long period. Studying on a single-domain protein can be a remark to understand the protein folding mechanism in general. Recently, we folded the Protein G B1 Domain (PGB1) by an over-critical folding process, which was developed by our lab, and studied the conformational changes in each folding state. PGB1 is a small protein with 56 residues, and is an IgG-binding domain of protein G. Because PGB1 contains the basic folding elements in a short sequence of amino acid without disulfide bonds, making it an excellent model for protein folding studies. The intrinsic Trp43 fluorescence of PGB1 and the acrylamide-quenching fluorescence showed that the PGB1 folding is a two-state reaction. However, the molecular diameter changes during the folding process indicated a folding intermediate exists in the PGB1 folding process. The FRET experiment, with Trp/IAEDANS as fluorophore pairs, showed that the β-hairpin 2 attaches to the α-helix long before the β-hairpin 1 formation. All the results together suggest the PGB1 folding process is a multi-state reaction. Overall, we were successful to reveal the folding process of PGB1 by FRET analysis.
URI: http://140.113.39.130/cdrfb3/record/nctu/#GT079828510
http://hdl.handle.net/11536/47718
Appears in Collections:Thesis


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