Selinger L B, McGregor N F, Khachatourians G G, Hynes M F
Research Station, Agriculture Canada, Lethbridge, Alberta.
J Bacteriol. 1990 Jun;172(6):3290-7. doi: 10.1128/jb.172.6.3290-3297.1990.
Genetic analysis of the closely related nonconjugative plasmids pUB110 and pBC16 has demonstrated that the open reading frame beta (ORF-beta) region in pUB110 and the corresponding homologous region in pBC16 are essential for mobilization of these plasmids by pLS20 or its derivatives. Deletions in this region or insertions that interrupted ORF-beta severely impaired or eliminated the mobilization of pUB110::pUC18 and pBC16::pUC18 hybrids. In contrast, a hybrid in which pUC18 was inserted into pBC16 at a point outside ORF-beta transferred at a frequency comparable to that of intact pUB110 or pBC16 (10(-4) transcipients per donor cell). The defect of most transfer-deficient (Mob-) hybrid plasmids could be complemented by an intact sister plasmid (i.e., pBC16 for pUB110::pUC18 Mob- hybrids). The inability to complement certain constructs suggested that the origin of transfer might be located in an area 5' to ORF-beta. Furthermore, cloning the region 5' to ORF-beta onto a nonmobilizable pC194::pUC18 construct resulted in a hybrid plasmid, pUCCoriTBC16, that could be mobilized with complementation. These results indicate that mobilization of pUB110 and pBC16 by conjugative helper plasmids requires ORF-beta in trans and at least one other region, including the RSA sequence, which presumably functions as an origin of transfer, in cis.
对密切相关的非接合性质粒pUB110和pBC16的遗传分析表明，pUB110中的开放阅读框β（ORF-β）区域以及pBC16中的相应同源区域对于这些质粒被pLS20或其衍生物进行动员至关重要。该区域的缺失或中断ORF-β的插入严重损害或消除了pUB110::pUC18和pBC16::pUC18杂种的动员能力。相比之下，将pUC18插入到ORF-β以外的pBC16中的杂种以与完整的pUB110或pBC16相当的频率转移（每个供体细胞有10^(-4)个转导子）。大多数转移缺陷（Mob-）杂种质粒的缺陷可以由完整的姐妹质粒互补（即，对于pUB110::pUC18 Mob-杂种为pBC16）。无法互补某些构建体表明转移起点可能位于ORF-β 5'端的一个区域。此外，将ORF-β 5'端的区域克隆到不可动员的pC194::pUC18构建体上产生了一个杂种质粒pUCCoriTBC16，其可以在互补的情况下被动员。这些结果表明，通过接合辅助质粒对pUB110和pBC16的动员在反式中需要ORF-β，并且在顺式中至少需要一个其他区域，包括可能作为转移起点的RSA序列。
