Brasch M A, Meyer R J
J Bacteriol. 1986 Aug;167(2):703-10. doi: 10.1128/jb.167.2.703-710.1986.
DNA involved in the mobilization of broad-host-range plasmid R1162 was localized to a region of 2.7 kilobases within coordinates 3.4 to 6.1 kilobases on the R1162 map. By examining the transfer properties of plasmids containing cloned fragments of DNA from within this region, we showed that at least four trans-active products and a cis-active site (oriT) were involved in mobilization. A cloned DNA fragment of 155 base pairs was capable of providing full oriT activity. This fragment was located within 600 base pairs of DNA containing the origin of replication of R1162, and its nucleotide sequence and that of neighboring DNA were determined. Activation of oriT required R1162-encoded, trans-acting products. Deletions which resulted in the loss of one or more of these had a variable effect on transfer efficiency and indicated the presence of both essential and nonessential Mob products. Regions encoding these products flanked oriT and in one case appeared to overlap a gene essential for plasmid replication. The implications of these findings with respect to the broad host range of R1162 are discussed.
参与广宿主范围质粒R1162转移的DNA定位于R1162图谱上坐标3.4至6.1千碱基之间的一个2.7千碱基的区域。通过检测含有该区域内DNA克隆片段的质粒的转移特性，我们发现至少有四种反式作用产物和顺式作用位点（oriT）参与了转移过程。一个155个碱基对的克隆DNA片段能够提供完整的oriT活性。该片段位于包含R1162复制起点的600个碱基对的DNA范围内，并测定了其核苷酸序列及相邻DNA的序列。oriT的激活需要R1162编码的反式作用产物。导致这些产物中一种或多种缺失的缺失突变对转移效率有不同影响，表明存在必需和非必需的Mob产物。编码这些产物的区域位于oriT两侧，在一种情况下似乎与质粒复制所必需的一个基因重叠。讨论了这些发现对R1162广宿主范围的意义。
