Kokkori Sofia, Apostolidi Maria, Tsakris Athanassios, Pournaras Spyros, Stathopoulos Constantinos, Dinos George
Department of Biochemistry, School of Medicine, University of Patras, Patras, Greece.
Department of Microbiology, Medical School, University of Athens, Athens, Greece.
Antimicrob Agents Chemother. 2014 Aug;58(8):4651-6. doi: 10.1128/AAC.02835-14. Epub 2014 Jun 2.
Linezolid-dependent growth was recently reported in Staphylococcus epidermidis clinical strains carrying mutations associated with linezolid resistance. To investigate this unexpected behavior at the molecular level, we isolated active ribosomes from one of the linezolid-dependent strains and we compared them with ribosomes isolated from a wild-type strain. Both strains were grown in the absence and presence of linezolid. Detailed biochemical and structural analyses revealed essential differences in the function and structure of isolated ribosomes which were assembled in the presence of linezolid. The catalytic activity of peptidyltransferase was found to be significantly higher in the ribosomes derived from the linezolid-dependent strain. Interestingly, the same ribosomes exhibited an abnormal ribosomal subunit dissociation profile on a sucrose gradient in the absence of linezolid, but the profile was restored after treatment of the ribosomes with an excess of the antibiotic. Our study suggests that linezolid most likely modified the ribosomal assembly procedure, leading to a new functional ribosomal population active only in the presence of linezolid. Therefore, the higher growth rate of the partially linezolid-dependent strains could be attributed to the functional and structural adaptations of ribosomes to linezolid.
最近有报道称，携带与利奈唑胺耐药相关突变的表皮葡萄球菌临床菌株出现了利奈唑胺依赖性生长。为了在分子水平上研究这种意外行为，我们从一株利奈唑胺依赖性菌株中分离出活性核糖体，并将其与从野生型菌株中分离出的核糖体进行比较。两种菌株均在有无利奈唑胺的情况下培养。详细的生化和结构分析揭示了在利奈唑胺存在下组装的分离核糖体在功能和结构上的本质差异。发现源自利奈唑胺依赖性菌株的核糖体中肽基转移酶的催化活性明显更高。有趣的是，相同的核糖体在无利奈唑胺的情况下在蔗糖梯度上呈现出异常的核糖体亚基解离图谱，但在用过量抗生素处理核糖体后该图谱得以恢复。我们的研究表明，利奈唑胺很可能改变了核糖体的组装过程，导致形成了仅在利奈唑胺存在时才具有活性的新的功能性核糖体群体。因此，部分利奈唑胺依赖性菌株较高的生长速率可能归因于核糖体对利奈唑胺的功能和结构适应性。
