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標題: | Erwinia stewartii 質體pSW100 和pSW140的分析 Analysis of Erwinia stewartii Plasmids pSW100 and pSW140 |
作者: | Han-Chang Chang 張漢章 |
出版年 : | 1994 |
學位: | 碩士 |
摘要: | Erwinia stewartii是革蘭氏陰性細菌,屬於腸內細菌科(Enterobacteriaceae)。由不同地區純化出來的Erwinia stewartii菌株,通常都有一個特性,就是一個菌體內會帶有許多不同之質體,一般約有8-13個,大小自4kb到320kb,所有的質體DNA約佔細菌全部DNA的四分之一含量,這些質體必定是以互不幹擾的方式進行複製,而能相容於同一個細胞內。為了探討這些質體的複製方式,首先以不同的限制?切割Erwinia stewartii Sw2中的質體,並接合在自pUC4-KISS純化出的kanamycin cartridge,送入大腸桿菌細胞,以抗生素篩選,所得到的選殖株,應該同時帶有抗生素基因和質體複製起點。得到二個選殖株pSWE3(3.7kb),pSWP5(3.2kb)。經由hybridization知道pSWE3是來自pSW140,pSWP5是來自pSW100。再以DNA定序法分別定出其序列,經過實驗分析,知道pSWE3上有7個iterons,其與incompatibility有關,在此區域內有一主導36kDa蛋白之open reading frame,其功能可能是製造與複製有關之蛋白,實驗證明此open reading frame被破壞後,質體就無法進行複製。repA RNA的5’端位於距離repA基因的起始密碼上游之130bP位置。repA起動子的區域含有2個iterons,所以repA的表現可能會受到RepA的自動調節(autoregulation)。而Pswp5的複製區域和pl5A, ColEl, Co1A之複製區域很相似,相似性分別為p15A(78%), ColEl(70%), ColA(67%),尤其在RNAI和RNAII的起動子區域序列是完全相同的。可見pSWP5的複製方式應該也是由RNAI和RNAII形成hybrid的結構調控複製之進行,因此pSWP5是以inhibitor targeting mechanism進行複製。另外又發現pSWP5能和pSL525(ColEl ori)或pACYC184(p15A ori)相容,這可能是因為它們的RNAI,RNAII序列有差異所造成。 Erwinia stewaitii is a gram-nagative bacterium, belonging to the family of Enterobacteriaceae. E. stewaitii strains usually contain 8-13 compatible plasmids, ranging from 4 kb to 320 kb. The total length of these plasmids may comprise 25% of the bacterial genome. These plasmids can replicate autonomously in E. stewartii and in Escherichia coli. The origins of replication of the two plasmids of E. stewartii SW2, pSW100 and pSW140, were cloned by ligating the restriction fragments of the plasmids of E. stewartii and a kanamycin-resistant gene isolated from pUC4-KISS. Results showed that pSWE3 (3.7 kb) and pSWP5 (3.2 kb) contained origins of replication of pSW140 and pSW100, respectively. DNA sequencing analysis revealed that the region essential for the replication of pSW140 contains seven 16-bp perfect repeats (iterons). These repeats are essential for the incompatibility and for the regulation of the replication of the plasmid. An open reading frame, encoding a 36kDa protein, was also present in the region. Deletion in this open reading frame abolishes the replication function. The replication is restored, if this open reading frame is complemented in trans, suggesting that this open reading frame may encode a protein (RepA) required for plasmid replication. The 5’ terminus of the repA transcript is located 130bp upstream from the initiation codon of repA gene, as determined by primer extension. The”-10” and the “-35” regions of the repA promoter contain two iterons, suggesting that the expression of repA may be autoregulated by RepA. The region required for the replication of pSW100 contains a sequence highly homologous to the origins of replication of ColE1-like plasmids, suggesting that pSW100 uses the inhibitor targeting mechanism for replication. This region is 78%, 70%, and 67% homologous to origins of replication of plasmids p15A, ColE1, and ColA, respectively. Due to sequence differences in the RNAI region, pSW100 is compatible with p15A and ColE1 in E. coli. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/76096 |
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顯示於系所單位: | 植物科學研究所 |
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