del Solar G H, Puyet A, Espinosa M
Nucleic Acids Res. 1987 Jul 24;15(14):5561-80. doi: 10.1093/nar/15.14.5561.
We have characterized a region in the streptococcal plasmid pLS1 located between nucleotides 4103 and 4218 which is a signal involved in the conversion of single stranded intermediates of replication to double stranded plasmid forms. This region has a large axis of dyad symmetry resulting in the formation of a secondary structure as revealed by the location of endonuclease S1-cleavage sites in supercoiled covalently closed circular pLS1 DNA. Deletions affecting this region caused a fivefold reduction in plasmid copy number, plasmid instability and the accumulation of single-stranded DNA intermediates. The conversion signal of pLS1 has homologues in other staphylococcal plasmids, sharing a consensus sequence located in the loop of the signal. Computer assisted analysis showed that the signal detected in pLS1 has a high degree of homology with the complementary strand origin of the Escherichia coli single stranded bacteriophages phi X174 and M13.
我们已经对链球菌质粒pLS1中位于核苷酸4103和4218之间的一个区域进行了特性分析，该区域是参与将复制的单链中间体转化为双链质粒形式的信号。该区域具有较大的二元对称轴，如超螺旋共价闭合环状pLS1 DNA中的核酸酶S1切割位点所示，会形成二级结构。影响该区域的缺失导致质粒拷贝数减少五倍、质粒不稳定以及单链DNA中间体的积累。pLS1的转化信号在其他葡萄球菌质粒中有同源物，在信号环中共享一个共有序列。计算机辅助分析表明，在pLS1中检测到的信号与大肠杆菌单链噬菌体phi X174和M13的互补链起源具有高度同源性。
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