本文選題：ksgA + 藍細菌�。� 參考：《華中農(nóng)業(yè)大學》2015年碩士論文

【摘要】：作為地球上最古老的生物之一,藍細菌種類多樣,是生態(tài)環(huán)境中重要的微生物類群。目前,關于藍細菌的分子進化還存在很多爭議和空白。KsgA/Dim1家族的雙甲基化酶是一個典型的S-腺苷甲硫氨酸(SAM)依賴的Ⅰ類甲基轉移酶,催化核糖體小亞基rRNA末端莖環(huán)上兩個相鄰腺嘌呤的雙甲基化。這兩個堿基的雙甲基化修飾是核糖體小亞基rRNA僅有的三個高度保守的堿基修飾中的兩個。本研究對已測序的37種藍細菌KsgA甲基化酶基因和16S rDNA進行了序列比對和進化分析,結果顯示藍細菌ksgA基因與16S rDNA進化分支高度相似,且體現(xiàn)出藍細菌進化的聚類特征。本研究同時對藍細菌KsgA蛋白進行了結構預測、保守模體及催化活性位點分析,顯示藍細菌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構：均包含N端與C端兩個結構域,N端是典型而保守的SAM依賴的甲基轉移酶結構域；C端的序列和結構則均呈現(xiàn)相對多樣化。根據(jù)序列分析和結構預測的結果,本研究中選擇克隆了單細胞的集胞藍細菌Synechocystis sp.PCC6803.絲狀能分化異形胞固氮的魚腥藍細菌Anabaena sp.PCC120,以及單細胞棒狀的細長聚球藍細菌Synechococcus elongates sp.PCC7942的ksgA基因,分別對大腸桿菌的ksgA突變體進行異源互補以初步驗證ksgA在藍細菌中的功能,實驗中發(fā)現(xiàn)它們均能在一定程度上互補大腸桿菌ksgA基因突變體的表型。本研究通過對藍細菌中KsgA/Dim1蛋白質家族的研究為進一步理解蛋白質功能與結構協(xié)同進化的機制和藍細菌的演化歷程補充了理論依據(jù)并提供了實驗證據(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.
【學位授予單位】：華中農(nóng)業(yè)大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：Q936

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相關博士學位論文 前1條

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本文編號：2001260