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研究生:李元馭
研究生(外文):Yuan-Yu Lee
論文名稱:影響cei-mRNA專一性切割因子的量化測定;大腸桿菌素胞膜位移有關之基因的轉錄表現
論文名稱(外文):Quantitative analysis of the factors affecting the specific cleavage of the cei-mRNA and the transcriptional expression of genes related to the translocation process of colicin across the membrane
指導教授:翟建富翟建富引用關係
指導教授(外文):Kin-Fu Chak
學位類別:碩士
校院名稱:國立陽明大學
系所名稱:生物化學研究所
學門:生命科學學門
學類:生物化學學類
論文種類:學術論文
論文出版年:2001
畢業學年度:89
語文別:中文
中文關鍵詞:大腸桿菌素反轉錄聚合酵素連鎖反應定量法胞膜移位
外文關鍵詞:colicinquantitative RT-PCR assaytranslocation
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第一部份
腸道菌在生長環境中會遇到許多複雜的自然化學訊息 ( physicochemical signals ),如:溫度、pH值、滲透壓、養份和有毒物質,藉由這些環境因素的整合使腸道菌在腸道中找到最適合的生長環境。大腸桿菌可藉由大腸桿菌素的產量增多來增加自己生存和防禦的機會。
大腸桿菌素是由大腸桿菌所產生的一種質體編碼殺菌毒素,其作用範圍為大腸桿菌及相近的腸桿菌科細菌。E7大腸桿菌素操縱子是由三個基因所組成,分別為大腸桿菌素基因 (cea)、免疫蛋白基因 (cei) 及溶菌蛋白基因 (cel),而這操縱子的表現是受到宿主SOS反應系統的調節。cei基因的產物-免疫蛋白,可以中和其上游 cea基因產物的毒性,以保護宿主;而 cel基因的產物-溶菌蛋白可以將大腸桿菌素和免疫蛋白的複合體運送到菌體外,但當它大量表現時則會造成宿主細胞的溶解而死亡。因此,操縱子基因間的協調表現是很重要的。
對於免疫蛋白 (ImmE7) 最清楚的功能為可以中和大腸桿菌素的毒性。在先前的研究發現,多元轉錄物cea-cei-cel在cei上有一主要的特定點斷裂 (major site-specific cleavage) 的現象,推測此定點斷裂與操縱子的表現調控有關。本論文以探討在cei上特定的斷裂 (site-specific cleavage) 情形會不會受到環境因素的影響和影響的程度為主要的研究方向。
利用反轉錄聚合酵素連鎖反應定量法 (quantitative RT-PCR assay) 對Mitomycin C誘導、增加E7大腸桿菌素操縱子產量、高溫、高pH值等不同環境因素影響 cei上特定斷裂的程度作探討。結果顯示,SOS反應對 cei上特定斷裂現象是一個強烈的訊息。 cei上特定斷裂現象隨著E7大腸桿菌素操縱子產量而變化。溫度和 pH值影響 cei上特定斷裂現象的程度較緩和。這些結果顯示,環境因素影響大腸桿菌素 ColE7 operon上cei特定斷裂的機制有兩個: (一) cei上特定斷裂的情形會隨著E7大腸桿菌素操縱子產量而變化,如:增加E7大腸桿菌素操縱子產量。(二) 當大腸桿菌素ColE7操縱子的表現突然過量時,會引發菌體中某些機制去對應大腸桿菌素操縱子大量表現的強烈反應,如:mitomycin C的誘導, 高溫, 高pH值之下。在未來的工作中,將進一步探討目前已知細菌用來對環境做適應調節的系統與 cei上特定斷裂現象的關係,及所參與的因子和調控的機制。
第二部份
大腸桿菌素E7是去氧核醣核酸酵素型式的細菌毒素。當大腸桿菌遭遇環境壓力時會分泌此毒素殺害其它細菌以增加其在此環境中的競爭力。當大腸桿菌素在細胞中被轉譯時,同時產生免疫蛋白質與毒性區域結合以中和其毒性因而避免此毒素對菌體自身所造成傷害。經轉譯後,大腸桿菌素 (ColE7)與免疫蛋白 (ImmE7) 會以異體複合物的形式分泌到細胞外。大腸桿菌素進入細胞內必需藉由一些外膜接受器 (如:BtuB)。然後,大腸桿菌素進入胞膜間區 (periplasmic space) 是利用Tol系統並有許多不同的胞膜間區或內膜蛋白質的參與其中。最後,當大腸桿菌素到達胞膜間區之後,大腸桿菌素會依據其不同的毒性特質,造成細胞的受損,甚至死亡;本論文以探討大腸桿菌素ColE7的胞膜移位過程還有那些不同的胞膜間區或內膜蛋白質參與為主要的研究方向。
利用transposon mutagenesis法來尋找參與translocation相關的基因,並尋求參與translocation相關的蛋白質。結果,發現有56個被transposon插入genomic DNA的菌株;接著,發現有36個被transposon破壞的菌株是可以抗colicin的毒殺;最後,對插入的基因做定序後確定各突變株只有一個transposon插入到genomic DNA中,得到被插入的基因都不含胞膜蛋白有關的基因,然而這些突變株如何影響ColE7的胞膜位移,這是值得做進一步的探討。
接著,利用反轉錄聚合酵素連鎖反應定量法 ( quantitative RT-PCR assay )來測定抗colicin毒殺的突變菌株中的有關胞膜位移基因 ( 包括btuB, ompC, ompF, pa l) 的表現情形。結果發現在每一個抗colicin毒殺的菌株中btuB, ompC, ompF, pal的表現量和野生型 ( wild type ) 比較有所不同。因此證明所測定的突變基因與大腸桿菌素胞膜位移過程有關。
總合以上的結果,我們已發現一些新型基因與大腸桿菌素胞膜位移過程有關。未來工作中,將測定每一突變菌株對大腸桿菌素的胞膜位移所做成的影響,再從突變菌株定出些基因和蛋白與野生株之異同。最後,再研究彼此間的關係和受那些因子的調控,藉以鉤勒出一個完整的大腸桿菌素ColE7胞膜位移過程的機制。

中文摘要…………………………………………….……………………….…Ⅰ
英文摘要…………………………………………….…………………………Ⅳ
壹、序論………………………………………………………………….1 ~ 13
第一部份
一、背景介紹………………………………………………………….…1
(一)大腸桿菌素ColE7基因與其操縱子上其它基因的功能……..1
(二)大腸桿菌素的分類………………………………………….…..2
(三)大腸桿菌素的作用機制………………………………………...3
二、大腸桿菌素E7質體之特性………………………………….…..…3
三、大腸桿菌素E7操縱子基因表現之調節…………………………...4
四、大腸桿菌素質體之運用及本實驗室ColE7-K317質體研究之概況…………………………………………………………………….5
五、環境因素對cei上特定的斷裂 (site-specific cleavage) 情形之影響………………………………………………………….……..…..7
六、實驗目的………………………………………………….…..……...8
第二部份
一、大腸桿菌素進入敏感細胞之途徑………………………..…………9
二、目前已知參與大腸桿菌素ColE7的胞膜移位過程所需蛋白之探討………………………………………….....……………….…..…10
三、目前對於大腸桿菌素進入敏感細菌 (sensitive bacteria) 移位過程 (translocation process) 研究之概況…………………...…………...11
四、實驗目的………………………………………………….…..……...12
貳、實驗材料與方法…………………………………………………….14 ~ 46
一、細菌菌株………………………………………………….…..…… 14
二、質體及其建構…………………………………………….…..…… 14
三、化學藥品與酵素………………………………….…………..…… 15
四、一般分生研究的方法…………………………………..….... 17 ~ 26
(一)細菌培養………………………………………………..……... 17
(二)在大腸桿菌中質體DNA之分離與純化……………..……..... 18
(三)大腸桿菌中全部DNA (total genomic DNA) 之分離與純化...20
(四)聚合酵素鏈鎖反應…………………………………………..... 21
(五)限制酵素的切割……………………………..……………..…. 22
(六)CIAP處理…………………………………..…………………..22
(七)Klenow反應處理…………………………………………..…...22
(八)DNA的連接反應………………………………………..…..… 23
(九)洋菜膠體電泳……………………………...……………...……24
(十)從洋菜膠中回收DNA片段及純化…………...…………….... 24
(十一)細菌的轉形作用……………………………………...…….. 25
(十二)選殖菌株之篩選-細菌質體之快速篩選法………………… 27
五、蛋白質電泳……………………………..……………………… 28 ~ 32
(一)SDS-聚丙醯胺膠電泳……….…………………………………28
(二)蛋白質染色……………………………………………………..31
六、西方墨點測試………………………………………………………...32
七、遠西墨點測試………………………………………………………...33
八、Colicin活性測試 (Colicin activity test)……………………………..34
九、RNA的抽取 (RNA isolation)……………………………….……….34
十、反轉錄聚合酵素鏈鎖反應…………………………………..……….35
參、結果……………………………………………………….…………. 37 ~ 50
第一部份
一、建立cei-mRNA上特定斷裂 (site-specific cleavage) 程度的定量方法…….……………………………………………………………… 37
二、Mitomycin C的誘導之下對免疫基因mRNA上特定點斷裂(site-specific cleavage) 現象的影響…………………………..…… 39
三、在沒有DNA損壞的情況下觀察在菌體中total mRNA量對免疫基因mRNA上特定點斷裂 (site-specific cleavage) 現象的影響……….41
四、高溫下對免疫基因mRNA上特定點斷裂 (site-specific cleavage) 現象的影響………………………………………………………….….43
五、高pH值下對免疫基因mRNA上特定點斷裂(site-specific cleavage) 現象的影響……………………………………………………….….44
六、環境因素對免疫基因mRNA上特定點斷裂(site-specific cleavage) 現象的影響之比較………………………………………………….….45
第二部份
一、以transposon mutagenesis法來尋找與translocation相關的基因藉此完成一個完整的桿菌素胞膜移位過程的模式…….……………… 46
二、大腸桿菌素ColE7的胞膜移位過程所需基因轉錄表現的定量方法……………………………………………………………….…… 48
三、參與大腸桿菌素ColE7胞膜移位過程所需基因與抗colicin毒殺關係之探討………………………………………………………….….49
肆、討論………………………………………………………...……..…. 51 ~ 64
第一部份
一、影響RNA斷裂現象發生可能的環境因素…….…………………… 51
(一)Mitomycin C的誘導之下的影響……………………………...... 52
(二)增加菌體中大腸桿菌素ColE7操縱子表現量之影響………..... 53
(三)高溫下的影響……………………………………………………..54
(四)高pH值下的影響………………………………………….…..... 55
二、環境因素對細菌生存的影響…………………….………………..…56
三、未來工作……………….………………………………………….….57
第二部份
一、可能參與大腸桿菌素ColE7運送的蛋白質之探討…….………..…59
(一)以transposon mutagenesis法找到之基因可能參與大腸桿菌素運送的機制……………………………..…………………………..…...59
二、可能影響大腸桿菌素ColE7的胞膜移位過程的機制…………...…62
三、未來工作……………….…………………………………………..….64
伍、圖表………………………………………………..…………………... 65 ~ 88
陸、參考文獻…………………………………………………….…….……89 ~ 97

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