Structure-guided Disruption of the Pseudopilus Tip Complex Inhibits the Type II Secretion System of Pseudomonas Aeruginosa
Pseudomonas aeruginosa, a Gram-negative bacterium, is known for its opportunistic way of infecting humans as well as other animals. Due to its pathogenicity, P. aeruginosa has been considered to be one of the top bacterial threats by the World Health Organization. It tends to infect targets with reduced immune systems and various tissues and organs, causing pneumonia, necrosis, and intestinal infection etc. P. aeruginosa, like other bacteria, has evolved different types of secretion systems to secrete a wide spectrum of virulence factors, especially various proteins and nucleotides. Bacteria use these molecular ‘weapons’ not only to adapt for surviving environments in the hosts but also to penetrate into hosts tissues to facilitate their colonization and proliferations, which further results in infections. To date, out of seven identified types of bacterial secretion systems, the Type II secretion system (T2SS) is one of the best-characterized secretion systems, known for its capability of translocating large, structured protein molecules from the periplasm though the outer membrane into the extracellular milieu. In P. aeruginosa, the T2SS is established through the synergistic combination of four structural assemblies formed by twelve Xcp proteins. These four subcomplexes, from the perspective of function, can be divided into platform, engine, channel and piston, in which the piston, called pseudopilus, is of pivotal importance in the system as its tip complex, comprised by XcpU, -V, -W and -X, recognizes and binds to various virulence factors. Aiming to better clarify the function-dependent structural features of this pseudopilus tip, we utilized X-ray protein crystallography to fully depict the architecture of the ternary complex of XcpVWX as well as to identify the core complex of XcpVW. The reconstruction of the entire tip complex was done using small-angle X-ray scattering, which exhibits an overall architecture of the pseudopilus tip and the plausible working model during the secretion. Through the elucidation of the detailed interaction interface of XcpV and -W, we developed two inhibitory peptides and four inhibitory compounds. It is confirmed that these structure-based molecules can interfere the interaction between XcpV and -W and compromise the pseudopilus tip complex. Due to the critical role of the XcpVW complex to the Type II secretion, the disruption of the XcpVW complex leads to the inhibition of the entire Type II secretion system. Using Caenorhabditis elegans as an investigation model, our research shows that the virulence of P. aeruginosa towards C. elegans has been reduced in the presence of the structure-based inhibitory molecules and that these molecules are able to alleviate the infection.
URI for this recordhttp://hdl.handle.net/1974/24845
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