Boyd A C, Sherratt D J
Mol Gen Genet. 1986 Jun;203(3):496-504. doi: 10.1007/BF00422076.
Mobilization of the plasmid ColE1 from cells containing a conjugative plasmid (such as F) requires the synthesis of ColE1 mob proteins, and the presence, in cis, of bom (basis of mobility), a region of ColE1 containing the origin of transfer (oriT). The process of ColE1 transfer is thought to resemble that of the conjugative plasmid F, although the plasmids share little sequence homology. In F, conjugation is preceded by a strand-specific nicking event at oriT. The nicked strand is then conducted to the recipient with the 5' end leading. This is believed also to occur with ColE1, but direct biochemical confirmation has been precluded by its small size (6.65 kb). To test this hypothesis genetically, a novel method, using a lambda dv-based vector, has been devised to site-specifically integrate bom (or any other cloned sequence) into the chromosome of Escherichia coli. When provided with suitable mobilizing plasmids, such strains were found to transfer the chromosome in a polar way. From these data, the orientation of transfer of ColE1 was deduced and shown to be analogous to F.
从含有接合质粒（如F）的细胞中动员质粒ColE1需要合成ColE1迁移蛋白，以及顺式存在的bom（迁移基础），即ColE1中包含转移起点（oriT）的区域。尽管ColE1与接合质粒F的序列同源性很低，但ColE1的转移过程被认为与F相似。在F质粒中，接合之前在oriT处发生链特异性切口事件。然后带切口的链以5'端在前的方式被转移到受体细胞。人们认为ColE1的情况也是如此，但由于其尺寸较小（6.65 kb），一直无法进行直接的生化证实。为了从遗传学角度验证这一假设，人们设计了一种新方法，利用基于λdv的载体将bom（或任何其他克隆序列）位点特异性整合到大肠杆菌染色体中。当这些菌株携带合适的动员质粒时，发现它们以极性方式转移染色体。根据这些数据，推断出ColE1的转移方向，并表明其与F质粒类似。
