Centre for Host-Microbiome Interactions, Faculty of Dental, Oral & Craniofacial Sciences, King's College London, London, UK; School of Biological and Chemical Sciences, Queen Mary University of London, London, UK.
Centre for Host-Microbiome Interactions, Faculty of Dental, Oral & Craniofacial Sciences, King's College London, London, UK.
J Mol Biol. 2022 Dec 15;434(23):167871. doi: 10.1016/j.jmb.2022.167871. Epub 2022 Oct 28.
Porphyromonas gingivalis is a gram-negative oral anaerobic pathogen and is one of the key causative agents of periodontitis. P. gingivalis utilises a range of virulence factors, including the cysteine protease RgpB, to drive pathogenesis and these are exported and attached to the cell surface via the type IX secretion system (T9SS). All cargo proteins possess a conserved C-terminal signal domain (CTD) which is recognised by the T9SS, and the outer membrane β-barrel protein PorV (PG0027/LptO) can interact with cargo proteins as they are exported to the bacterial surface. Using a combination of solution nuclear magnetic resonance (NMR) spectroscopy, biochemical analyses, machine-learning-based modelling and molecular dynamics (MD) simulations, we present a structural model of a PorV:RgpB-CTD complex from P. gingivalis. This is the first structural insight into CTD recognition by the T9SS and shows how the conserved motifs in the CTD are the primary sites that mediate binding. In PorV, interactions with extracellular surface loops are important for binding the CTD, and together these appear to cradle and lock RgpB-CTD in place. This work provides insight into cargo recognition by PorV but may also have important implications for understanding other aspects of type-IX dependent secretion.
牙龈卟啉单胞菌是一种革兰氏阴性口腔厌氧菌，是牙周炎的主要致病因子之一。牙龈卟啉单胞菌利用多种毒力因子，包括半胱氨酸蛋白酶 RgpB，来驱动发病机制，这些因子通过 IX 型分泌系统（T9SS）被输出并附着在细胞表面。所有货物蛋白都具有保守的 C 端信号域（CTD），该信号域被 T9SS 识别，而外膜β桶蛋白 PorV（PG0027/LptO）可以与货物蛋白相互作用，因为它们被输出到细菌表面。我们使用溶液核磁共振（NMR）光谱学、生化分析、基于机器学习的建模和分子动力学（MD）模拟相结合的方法，从牙龈卟啉单胞菌中展示了一个 PorV:RgpB-CTD 复合物的结构模型。这是 T9SS 识别 CTD 的第一个结构见解，并展示了 CTD 中的保守基序如何成为介导结合的主要位点。在 PorV 中，与细胞外表面环的相互作用对于结合 CTD 很重要，这些相互作用似乎共同将 RgpB-CTD 抱在适当位置并锁定。这项工作提供了对 PorV 货物识别的深入了解，但也可能对理解其他依赖于 IX 型的分泌方面具有重要意义。
