CAJ | 학술논문

通常细菌间环型质粒在接合转移过程中,单链质粒DNA在质粒内部"oriT"接合转移起始位点发生缺刻.随后,打开的单链质粒DNA通过细胞膜的Ⅳ型分泌系统转移到受体菌中.但是,链霉菌中的接合型线型质粒带有游离3'端,5'端与末端蛋白结合,因而不能以细胞-细胞间方式转移单链缺刻DNA.报道了变铅青链霉菌线型质粒SLP2衍生的环型质粒,与SLP2一样可以高频高效接合转移,并鉴定了接合转移功能区.质粒有效的接合转移功能区包含6个共转录的基因,分别编码一个Tra样的DNA转移酶、胞壁水解酶、2个膜蛋白(可以与ATP结合蛋白相互作用)和一个功能未知的蛋白质.从SalⅠR-/M-向SalⅠR/M宿主转移的质粒频率下降表明,线型和环型的质粒都是以双链的形式转移的.上述研究结果表明SLP2衍生的线型质粒和环型质粒以相似的与细胞膜/胞壁功能相关的机理进行接合转移.
통상세균간배형질립재접합전이과정중,단련질립DNA재질립내부"oriT"접합전이기시위점발생결각.수후,타개적단련질립DNA통과세포막적Ⅳ형분비계통전이도수체균중.단시,련매균중적접합형선형질립대유유리3'단,5'단여말단단백결합,인이불능이세포-세포간방식전이단련결각DNA.보도료변연청련매균선형질립SLP2연생적배형질립,여SLP2일양가이고빈고효접합전이,병감정료접합전이공능구.질립유효적접합전이공능구포함6개공전록적기인,분별편마일개Tra양적DNA전이매、포벽수해매、2개막단백(가이여ATP결합단백상호작용)화일개공능미지적단백질.종SalⅠR-/M-향SalⅠR/M숙주전이적질립빈솔하강표명,선형화배형적질립도시이쌍련적형식전이적.상술연구결과표명SLP2연생적선형질립화배형질립이상사적여세포막/포벽공능상관적궤리진행접합전이.
Commonly, the interbacterial transfer of circular plasmids is initiated by nicking at an internal sequence, oriT, followed by transferring one strand as single-stranded DNA through a type Ⅳ secretion channel on cell membrane. In contrast, Streptomyces conjugative linear plasmids, containing a free 3'-end but a protein-capped 5'-end, can potentially undergo cell-to-cell transfer by transfer of non-nicked DNA. It was reported that circular derivatives of the Streptomyces lividans linear plasmid SLP2, as well as the parental linear plasmid itself can transfer efficiently. And the genetic requirements for such transfer was described. Efficient transfer of plasmid requires six co-transcribed SLP2 genes, encoding a Tra-like DNA translocase, cell wall hydrolase, two cell membrane proteins that interact with an ATP binding protein, and a protein of unknown function. Reduced transfer efficiency of plasmid from SalⅠ R-/M-to Sal Ⅰ R/M hosts argues that transfer of both the circular and linear forms of the plasmid involves double-stranded DNA. These results suggest that conjugal transfer occurs by a similar mechanism for SLP2-derived linear and circular plasmids, and cellular membrane/wall functions in the transfer process.