Chaouni L B, Etienne J, Greenland T, Vandenesch F
Département de Recherche en Bactériologie Médicale (UPRES 1655), Faculté de Médecine R. Laennec, Lyon, France.
Plasmid. 1996 Jul;36(1):1-8. doi: 10.1006/plas.1996.0025.
Tolerance of Staphylococcus lugdunensis to relatively high levels of cadmium is mediated by a 3117-bp plasmid, pLUG10. Sequencing reveals three major open reading frames (ORFs) in a single orientation. One ORF encompasses the origin of replication and its predicted product (RepL: 350 amino acids (aa)) shows 70% homology in its deduced aa sequence with Rep proteins of the pT181 family. A lagging strand conversion signal (palA) very similar to that of class 1 plasmids is present outside the rep-ori locus. The other two ORFs of 209 and 116 aa show 92.5% homology between their deduced aa sequences and the CadB and CadX peptides from the pOX6 plasmid of Staphylococcus aureus. The CadX-like peptide is 40% homologous to the S. aureus CadC product. Deletion of the C-terminal cadX gene by restriction enzyme digestion or frame-shift inactivation of the cadB gene reduced, but did not completely abolish, cadmium resistance. The two gene products may act cooperatively to confer cadmium resistance in S. lugdunensis.
路邓葡萄球菌对较高水平镉的耐受性由一个3117碱基对的质粒pLUG10介导。测序显示单个方向上有三个主要开放阅读框（ORF）。一个ORF包含复制起点，其预测产物（RepL：350个氨基酸（aa））在推导的氨基酸序列中与pT181家族的Rep蛋白有70%的同源性。一个与1类质粒非常相似的滞后链转换信号（palA）存在于rep - ori位点之外。另外两个分别为209和116个氨基酸的ORF，其推导的氨基酸序列与金黄色葡萄球菌pOX6质粒的CadB和CadX肽之间有92.5%的同源性。类CadX肽与金黄色葡萄球菌CadC产物有40%的同源性。通过限制酶消化缺失C端cadX基因或cadB基因的移码失活可降低但并未完全消除镉抗性。这两种基因产物可能协同作用赋予路邓葡萄球菌镉抗性。
