Brunton J, Bennett P, Grinsted J
J Bacteriol. 1981 Dec;148(3):788-95. doi: 10.1128/jb.148.3.788-795.1981.
We characterized pJB1, the plasmid previously reported to mediate beta-lactamase production in Haemophilus ducreyi. We studied its relationship to pMR0360 and RSF0885, the plasmids responsible for beta-lactamase production in Neisseria gonorrhoeae and Haemophilus parainfluenzae, respectively. Although pJB1 was maintained as a multicopy pool in Escherichia coli, it was not stably maintained in the absence of antibiotic selection. Electron microscope heteroduplex studies showed that it carried 100% of the transposable ampicillin resistance sequence TnA. This sequence was transposed to plasmid pUB307 at a low rate. Heteroduplexes between pMR0360 and pJB1 showed that they contained 3.3 megadaltons of homologous sequences. Two sets of nonhomologous sequences, one a TnA sequence and the other a non-TnA sequence, took the form of insertion loops. For plasmids pMR0360 and RSF0885, previously shown to be highly related, the nonhomologous sequences took the form of a substitution loop. We concluded that all three plasmids shared major portions of their sequences but differed in discrete segments. pJB1 was the first such plasmid to have a physically and functionally intact TnA sequence.
我们对pJB1进行了特征分析，该质粒先前报道可介导杜克雷嗜血杆菌产生β-内酰胺酶。我们研究了它与pMR0360和RSF0885的关系，这两种质粒分别是淋病奈瑟菌和副流感嗜血杆菌中负责产生β-内酰胺酶的质粒。虽然pJB1在大肠杆菌中以多拷贝形式存在，但在没有抗生素选择的情况下不能稳定维持。电子显微镜异源双链研究表明，它携带100%的转座型氨苄青霉素抗性序列TnA。该序列以低频率转座到质粒pUB307上。pMR0360和pJB1之间的异源双链表明它们含有3.3兆道尔顿的同源序列。两组非同源序列，一组是TnA序列，另一组是非TnA序列，呈插入环形式。对于先前已证明高度相关的质粒pMR0360和RSF0885，非同源序列呈替代环形式。我们得出结论，所有三种质粒共享其序列的主要部分，但在离散片段上有所不同。pJB1是第一个具有物理和功能完整TnA序列的此类质粒。
