Department of Microbiology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, 100191, China.
National Center for Health Professions Education Development, Beijing, 100191, China.
Sci Rep. 2019 Jul 1;9(1):9438. doi: 10.1038/s41598-019-45875-9.
Type VI secretion system (T6SS) is described as a macromolecular secretion machine that is utilized for bacterial competition. The gene clusters encoding T6SS are composed of core tss genes and tag genes. However, the clusters differ greatly in different pathogens due to the great changes accumulated during the long-term evolution. In this work, we identified a novel hypothetical periplasmic protein designated as AsaA which is encoded by the first gene of the T6SS cluster in the genus Acinetobacter. By constructing asaA mutant, we delineated its relative contributions to bacterial competition and secretion of T6SS effector Hcp. Subsequently, we studied the localization of AsaA and potential proteins that may have interactions with AsaA. Our results showed that AsaA in Acinetobacter baumannii (A. baumannii) localized in the bacterial periplasmic space. Results based on bacterial two-hybrid system and protein pull-down assays indicated that it was most likely to affect the assembly or stability of T6SS by interacting with the T6SS core protein TssM. Collectively, our findings of AsaA is most likely a key step in understanding of the T6SS functions in A. baumannii.
VI 型分泌系统（T6SS）被描述为一种用于细菌竞争的大分子分泌机器。编码 T6SS 的基因簇由核心 tss 基因和标签基因组成。然而，由于在长期进化过程中积累了巨大的变化，不同病原体之间的簇差异很大。在这项工作中，我们鉴定了一个新型的假定周质蛋白，命名为 AsaA，它由不动杆菌属 T6SS 簇的第一个基因编码。通过构建 asaA 突变体，我们描绘了它对细菌竞争和 T6SS 效应蛋白 Hcp 分泌的相对贡献。随后，我们研究了 AsaA 的定位以及可能与 AsaA 相互作用的潜在蛋白质。我们的结果表明，鲍曼不动杆菌（A.baumannii）中的 AsaA 定位于细菌周质空间。基于细菌双杂交系统和蛋白质下拉测定的结果表明，它最有可能通过与 T6SS 核心蛋白 TssM 相互作用来影响 T6SS 的组装或稳定性。总之，我们对 AsaA 的发现很可能是理解 A.baumannii 中 T6SS 功能的关键步骤。
