發(fā)布時(shí)間：2018-06-09 23:53

  本文選題：ksgA + 藍(lán)細(xì)菌��； 參考：《華中農(nóng)業(yè)大學(xué)》2015年碩士論文

【摘要】：作為地球上最古老的生物之一,藍(lán)細(xì)菌種類多樣,是生態(tài)環(huán)境中重要的微生物類群。目前,關(guān)于藍(lán)細(xì)菌的分子進(jìn)化還存在很多爭(zhēng)議和空白。KsgA/Dim1家族的雙甲基化酶是一個(gè)典型的S-腺苷甲硫氨酸(SAM)依賴的Ⅰ類甲基轉(zhuǎn)移酶,催化核糖體小亞基rRNA末端莖環(huán)上兩個(gè)相鄰腺嘌呤的雙甲基化。這兩個(gè)堿基的雙甲基化修飾是核糖體小亞基rRNA僅有的三個(gè)高度保守的堿基修飾中的兩個(gè)。本研究對(duì)已測(cè)序的37種藍(lán)細(xì)菌KsgA甲基化酶基因和16S rDNA進(jìn)行了序列比對(duì)和進(jìn)化分析,結(jié)果顯示藍(lán)細(xì)菌ksgA基因與16S rDNA進(jìn)化分支高度相似,且體現(xiàn)出藍(lán)細(xì)菌進(jìn)化的聚類特征。本研究同時(shí)對(duì)藍(lán)細(xì)菌KsgA蛋白進(jìn)行了結(jié)構(gòu)預(yù)測(cè)、保守模體及催化活性位點(diǎn)分析,顯示藍(lán)細(xì)菌KsgA甲基化酶與其它物種的KsgA/Dim1家族蛋白擁有高度相似的結(jié)構(gòu)：均包含N端與C端兩個(gè)結(jié)構(gòu)域,N端是典型而保守的SAM依賴的甲基轉(zhuǎn)移酶結(jié)構(gòu)域；C端的序列和結(jié)構(gòu)則均呈現(xiàn)相對(duì)多樣化。根據(jù)序列分析和結(jié)構(gòu)預(yù)測(cè)的結(jié)果,本研究中選擇克隆了單細(xì)胞的集胞藍(lán)細(xì)菌Synechocystis sp.PCC6803.絲狀能分化異形胞固氮的魚腥藍(lán)細(xì)菌Anabaena sp.PCC120,以及單細(xì)胞棒狀的細(xì)長(zhǎng)聚球藍(lán)細(xì)菌Synechococcus elongates sp.PCC7942的ksgA基因,分別對(duì)大腸桿菌的ksgA突變體進(jìn)行異源互補(bǔ)以初步驗(yàn)證ksgA在藍(lán)細(xì)菌中的功能,實(shí)驗(yàn)中發(fā)現(xiàn)它們均能在一定程度上互補(bǔ)大腸桿菌ksgA基因突變體的表型。本研究通過(guò)對(duì)藍(lán)細(xì)菌中KsgA/Dim1蛋白質(zhì)家族的研究為進(jìn)一步理解蛋白質(zhì)功能與結(jié)構(gòu)協(xié)同進(jìn)化的機(jī)制和藍(lán)細(xì)菌的演化歷程補(bǔ)充了理論依據(jù)并提供了實(shí)驗(yàn)證據(jù)。
[Abstract]:As one of the oldest organisms on the earth, cyanobacteria are an important microbial group in the ecological environment. At present, there are many controversies about the molecular evolution of cyanobacteria and the blank. KsgA / Dim1 family of dimethylases is a typical type I methyltransferase dependent on S- adenosine methionine (SAM). Catalyze the dimethylation of two adjacent adenines in the terminal stem ring of ribosomal small subunit rRNA. The dimethylation modification of these two bases is one of only three highly conserved modifications of ribosomal small subunit rRNA. In this study, the sequence alignment and evolution analysis of KsgA methylase gene and 16s rDNA of 37 species of cyanobacteria were carried out. The results showed that the ksgA gene of cyanobacteria was highly similar to the evolutionary branch of 16s rDNA, and showed the clustering characteristics of the evolution of cyanobacteria. At the same time, the structure of cyanobacteria KsgA protein was predicted, and the conserved motifs and catalytic activity sites were analyzed. It shows that the KsgA methylase of the cyanobacteria has a highly similar structure to the KsgA / Dim1 family of other species: both N-terminal and C-terminal N-terminal are typical and conserved SAM-dependent methyltransferase domain C-terminal sequences. And the structure is relatively diverse. According to the results of sequence analysis and structure prediction, Synechocystis sp. PCC6803 was cloned from single cell. Anabaena sp. PCC120, a filamentous bacterium capable of heterocytic nitrogen fixation, and ksgA gene of Synechococcus elongates sp. PCC7942, a single cell rod-like bacterium, were used to complement the ksgA mutants of Escherichia coli to preliminarily verify the function of ksgA in cyanobacteria. It was found that they could complement the phenotypes of E. coli ksgA gene mutants to some extent. In this study, the study of KsgA / Dim1 protein family in cyanobacteria provides theoretical basis and experimental evidence for further understanding the mechanism of protein function and structure coevolution and the evolution process of cyanobacteria.
【學(xué)位授予單位】：華中農(nóng)業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：Q936

【參考文獻(xiàn)】

相關(guān)博士學(xué)位論文 前1條

1 韓丹翔;藍(lán)藻念珠藻屬系統(tǒng)發(fā)育和分子進(jìn)化研究[D];中國(guó)科學(xué)院研究生院（水生生物研究所）;2006年

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本文編號(hào)：2001260