Lacks S A, Lopez P, Greenberg B, Espinosa M
J Mol Biol. 1986 Dec 20;192(4):753-65. doi: 10.1016/0022-2836(86)90026-4.
The streptococcal plasmid pMV158 and its derivative pLS1 are able to replicate and confer tetracycline resistance in both Gram-positive and Gram-negative bacteria. Copy numbers of pLS1 were 24, 4 and 4 molecules per genome in Streptococcus pneumoniae, Bacillus subtilis and Escherichia coli, respectively. Replication of the streptococcal plasmids in E. coli required functional polA and recA genes. A copy-number mutation corresponding to a 332 base-pair deletion of pLS1 doubled the plasmid copy number in all three species. Determination of the complete DNA sequence of pLS1 revealed transcriptional and translational signals and four open reading frames. A putative inhibitory RNA was encoded in the region deleted by the copy-control mutation. Two putative mRNA transcripts encoded proteins for replication functions and tetracycline resistance, respectively. The repB gene encoded a trans-acting, 23,000 Mr protein necessary for replication, and the tet gene encoded a very hydrophobic, 50,000 Mr protein required for tetracycline resistance. The polypeptides corresponding to these proteins were identified by specific labeling of plasmid-encoded products. The tet gene of pLS1 was highly homologous to tet genes in two other plasmids of Gram-positive origin but different in both sequence and mode of regulation from tet genes of Gram-negative origin.
链球菌质粒pMV158及其衍生物pLS1能够在革兰氏阳性菌和革兰氏阴性菌中复制并赋予四环素抗性。在肺炎链球菌、枯草芽孢杆菌和大肠杆菌中，pLS1的拷贝数分别为每个基因组24、4和4个分子。链球菌质粒在大肠杆菌中的复制需要功能性的polA和recA基因。对应于pLS1 332个碱基对缺失的拷贝数突变使该质粒在所有这三个物种中的拷贝数增加了一倍。pLS1完整DNA序列的测定揭示了转录和翻译信号以及四个开放阅读框。在拷贝控制突变所缺失的区域编码了一种假定的抑制性RNA。两个假定的mRNA转录本分别编码复制功能蛋白和四环素抗性蛋白。repB基因编码一种复制所必需的反式作用23000道尔顿蛋白，tet基因编码一种四环素抗性所必需的高度疏水的50000道尔顿蛋白。通过对质粒编码产物的特异性标记鉴定了与这些蛋白相对应的多肽。pLS1的tet基因与另外两个革兰氏阳性来源质粒中的tet基因高度同源，但在序列和调控方式上与革兰氏阴性来源的tet基因均不同。
