Shariq Mohd, Kumar Navin, Kumari Rajesh, Kumar Amarjeet, Subbarao Naidu, Mukhopadhyay Gauranga
Special Centre for Molecular Medicine, Jawaharlal Nehru University, New Delhi, India.
School of Life Sciences, Jawaharlal Nehru University, New Delhi, India.
PLoS One. 2015 Nov 13;10(11):e0142606. doi: 10.1371/journal.pone.0142606. eCollection 2015.
Helicobacter pylori are among the most successful human pathogens that harbour a distinct genomic segment called cag Pathogenicity Island (cag-PAI). This genomic segment codes for a type IV secretion system (Cag-T4SS) related to the prototypical VirB/D4 system of Agrobacterium tumefaciens (Ag), a plant pathogen. Some of the components of Cag-T4SS share homology to that of VirB proteins including putative energy providing CagE (HP0544), the largest VirB4 homologue. In Ag, VirB4 is required for the assembly of the system, substrate translocation and pilus formation, however, very little is known about CagE. Here we have characterised the protein biochemically, genetically, and microscopically and report that CagE is an inner membrane associated active NTPase and has multiple interacting partners including the inner membrane proteins CagV and Cagβ. Through CagV it is connected to the outer membrane sub-complex proteins. Stability of CagE is not dependent on several of the cag-PAI proteins tested. However, localisation and stability of the pilus associated CagI, CagL and surface associated CagH are affected in its absence. Stability of the inner membrane associated energetic component Cagβ, a VirD4 homologue seems to be partially affected in its absence. Additionally, CagA failed to cross the membrane barriers in its absence and no IL-8 induction is observed under infection condition. These results thus suggest the importance of CagE in Cag-T4SS functions. In future it may help in deciphering the mechanism of substrate translocation by the system.
幽门螺杆菌是最成功的人类病原体之一，它含有一个名为cag致病岛（cag-PAI）的独特基因组片段。这个基因组片段编码一种与植物病原体根癌农杆菌（Ag）的原型VirB/D4系统相关的IV型分泌系统（Cag-T4SS）。Cag-T4SS的一些成分与VirB蛋白具有同源性，包括假定的能量供应蛋白CagE（HP0544），它是最大的VirB4同源物。在农杆菌中，VirB4是系统组装、底物转运和菌毛形成所必需的，然而，人们对CagE知之甚少。在这里，我们通过生物化学、遗传学和显微镜方法对该蛋白进行了表征，并报告CagE是一种与内膜相关的活性NTP酶，有多个相互作用的伙伴，包括内膜蛋白CagV和Cagβ。通过CagV，它与外膜亚复合体蛋白相连。CagE的稳定性不依赖于所测试的几种cag-PAI蛋白。然而，在没有CagE的情况下，菌毛相关蛋白CagI、CagL和表面相关蛋白CagH的定位和稳定性会受到影响。内膜相关的能量成分Cagβ（一种VirD4同源物）在没有CagE的情况下稳定性似乎会受到部分影响。此外，在没有CagE的情况下，CagA无法穿过膜屏障，在感染条件下也未观察到白细胞介素-8的诱导。因此，这些结果表明CagE在Cag-T4SS功能中的重要性。未来，它可能有助于破译该系统底物转运的机制。
