Multidrug-resistant bacteria pose serious problems in hospital-acquired infections (HAIs). Most antibiotic resistance genes are acquired via conjugative gene transfer, mediated by type 4 secretion systems (T4SS). Although most multidrug-resistant bacteria responsible for HAIs are of Gram-positive origin, with enterococci being major contributors, mostly Gram-negative T4SSs have been characterized. Here, we describe the structure and organization of PrgL, a core protein of the T4SS channel, encoded by the pCF10 plasmid from Enterococcus faecalis. The structure of PrgL displays similarity to VirB8 proteins of Gram-negative T4SSs. In vitro experiments show that the soluble domain alone is enough to drive both dimerization and dodecamerization, with a dimerization interface that differs from all other known VirB8-like proteins. In vivo experiments verify the importance of PrgL dimerization. Our findings provide insight into the molecular building blocks of Gram-positive T4SS, highlighting similarities but also unique features in PrgL compared to other VirB8-like proteins.

耐多药细菌在医院获得性感染 (HAI) 中造成严重问题。大多数抗生素抗性基因是通过结合基因转移获得的，由 4 型分泌系统 (T4SS) 介导。尽管导致 HAI 的大多数耐多药细菌是革兰氏阳性菌，肠球菌是主要贡献者，但大多数革兰氏阴性 T4SS 已被表征。在这里，我们描述了 PrgL 的结构和组织，它是 T4SS 通道的核心蛋白，由粪肠球菌的 pCF10 质粒编码。PrgL 的结构与革兰氏阴性 T4SS 的 VirB8 蛋白相似。体外实验表明，单独的可溶结构域足以驱动二聚化和十二聚化，二聚化界面不同于所有其他已知的 VirB8 样蛋白。体内实验验证了 PrgL 二聚化的重要性。我们的研究结果提供了对革兰氏阳性 T4SS 分子构建模块的深入了解，突出了 PrgL 与其他 VirB8 样蛋白相比的相似性和独特性。