研究Min蛋白引導脂質雙層膜中物質產生二維疏密波之現象

Study of Min Protein-Induced Membrane Species Waves in vitro

杜育銘(Yu-Ming Tu)

指導教授 ： 趙玲

國立臺灣大學/工學院/化學工程學研究所/碩士(2015年)

https://doi.org/10.6342/NTU.2015.01208

摘要

在大腸桿菌中，Min蛋白藉由在細胞兩極來回的動態振盪，能調控細胞分裂的位置。目前也已發現Min蛋白之自發性構成之動態波現象，可以藉由將Min蛋白中的MinD，MinE和腺苷三磷酸 (Adenosine triphosphate)(ATP)加入以大腸桿菌的細胞膜所形成之支撐式脂雙層膜平台，而在體外重現。然而，Min蛋白如何與大腸桿菌中的脂質雙層膜作用，以及如何影響到其它膜中生物分子之機制依舊不甚清楚。在本論文中，我們假設Min蛋白嵌入膜和離開膜之動態情況會影響脂質雙層膜外層脂質膜中頭基區域的空間密度，進而間接促使頭基較一般脂質分子為大之膜中生物分子，會較喜好填補頭基部分較為寬鬆的區域，因而在密度寬鬆的區域造成累積，而在密度較為緊緻的區域則有減少的現象，進而能產生其隨時間空間變化的濃度分佈。在本系統中，我們利用大腸桿菌的細胞膜所形成之支撐式脂質雙層膜來在體外重建生物體內的系統，並從大腸桿菌內純化出Min蛋白，來系統性地討論Min蛋白對脂質雙層膜之影響。我們觀察到脂質雙層膜在加入MinD，MinE和腺苷三磷酸後，會形成動態的螺旋濃度分佈波形。螢光漂白回復測試法和影像處理分析進一步指出脂質雙層膜上的濃度分佈動態波形與Min蛋白形成的表面波形有不同的特性，顯示膜中物質之濃度分佈並非源自於與Min蛋白有直接之鍵結。我們以帶有螢光分子的數種膜中物質作為生物分子模型，並將之鑲嵌進脂質雙層膜的系統，在加入Min蛋白後，的確發現Min蛋白的動態震盪現象只會影響頭基部分較大之膜中生物分子。此實驗觀察符合我們的假設: Min蛋白的動態現象會影響到脂質雙層膜上的生物分子，並可能具有選擇性的影響特定生物分子。此結果也提供了一個 Min蛋白如何與其他膜中分子作用的可能機制。

關鍵字

Min 蛋白系統 ； 自組裝 ； 支撐式脂雙層膜平台 ； 動態圖形

並列摘要

In the bacterium Escherichia coli, the proper placement of the division site selection is regulated in part by the pole-to-pole oscillations of Min proteins. The oscillation dynamics emerges from the self-organization of MinD, MinE and ATP in vivo, which also forms planar surface waves on supported lipid bilayer in vitro. However, it is still unclear how the Min proteins affect the E. coli lipid membrane and interact with the other E. coli membrane proteins, even though how Min proteins interact with the membrane surface to generate the in vivo oscillations is a subject of intense study. We hypothesized that the spatial oscillations of Min protein systems could play a crucial role in changing lipid membrane dynamics and therefore indirectly influence the dynamics of other membrane associated species. We reconstituted the system on supported E. coli lipid bilayer platforms in order to systematically explore the underlying mechanism between lipid membranes and Min proteins. We observed fluorescently labeled lipids in the E. coli membranes moving in spiral waves after the addition of unlabeled MinD, MinE and ATP to the membranes. Fluorescence recovery after photobleaching (FRAP) and kymograph analyses showed that dynamics of the labeled lipid membrane waves had different characteristics from those of the Min protein waves. In the future, some E. coli signaling membrane proteins could be incorporated into the membrane to examine whether their movement or clustering can be influenced by the Min proteins-induced membrane waves. The result could provide us insights into the long-standing question about other possible function of the E. coli Min protein oscillation phenomenon.

並列關鍵字

Min system ； self-organization ； supported lipid bilayers ； dynamic pattern formation

參考文獻

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