Korem Moshe, Sheoran Abhineet S, Gov Yael, Tzipori Saul, Borovok Ilya, Balaban Naomi
Department of Human Microbiology, Sackler School of Medicine, Tel Aviv University, Israel.
FEMS Microbiol Lett. 2003 Jun 27;223(2):167-75. doi: 10.1016/S0378-1097(03)00326-4.
Staphylococcus aureus are Gram-positive bacteria and cause diverse serious diseases in humans and animals through the production of toxins. The production of toxins is regulated by quorum sensing mechanisms, where proteins such as RNAIII activating protein (RAP) are secreted by the bacteria and induce virulence. Antibodies to RAP have been shown to protect mice from infection, but the molecular structure of RAP was not known and hindered vaccine development. To characterize RAP, recombinant protein was made and tested for its ability to induce genes important for pathogenesis (agr). In addition, monoclonal antibodies were produced to identify its cellular localization. Results shown here indicate that RAP is a 277-aa protein that is an ortholog of the ribosomal protein L2. Like the native molecule, recombinant RAP activates the production of RNAIII (encoded by agr). Using RAP specific monoclonal antibodies we demonstrate that RAP is continuously secreted and while RAP is expressed also in other bacteria (like Staphylococcus epidermidis, Staphylococcus xylosus and Escherichia coli), it is secreted to the culture medium only by S. aureus. Our results show that the ribosomal protein L2 has an extraribosomal function and that when secreted RAP acts as an autoinducer of virulence to regulate S. aureus pathogenesis.
金黄色葡萄球菌是革兰氏阳性菌，通过产生毒素在人类和动物中引发多种严重疾病。毒素的产生受群体感应机制调控，诸如RNAIII激活蛋白（RAP）等蛋白质由细菌分泌并诱导毒力。已证明针对RAP的抗体可保护小鼠免受感染，但RAP的分子结构未知，这阻碍了疫苗的研发。为了表征RAP，制备了重组蛋白并测试其诱导对发病机制重要的基因（agr）的能力。此外，还制备了单克隆抗体以确定其细胞定位。此处所示结果表明，RAP是一种277个氨基酸的蛋白质，是核糖体蛋白L2的直系同源物。与天然分子一样，重组RAP激活RNAIII（由agr编码）的产生。使用RAP特异性单克隆抗体，我们证明RAP持续分泌，虽然RAP也在其他细菌（如表皮葡萄球菌、木糖葡萄球菌和大肠杆菌）中表达，但仅由金黄色葡萄球菌分泌到培养基中。我们的结果表明核糖体蛋白L2具有核糖体以外的功能，并且当分泌时，RAP作为毒力的自诱导物来调节金黄色葡萄球菌的发病机制。
