Pseudomonas aeruginosa is an opportunistic bacterium of which the main virulence factor is the Type III Secretion System. The ATPase of this machinery, PscN (SctN), is thought to be localized at the base of the secretion apparatus and to participate in the recognition, chaperone dissociation and unfolding of exported T3SS proteins. In this work, a protein-protein interaction ELISA revealed the interaction of PscN with a wide range of exported T3SS proteins including the needle, translocator, gate-keeper and effector. These interactions were further confirmed by Microscale Thermophoresis that also indicated a preferential interaction of PscN with secreted proteins or protein-chaperone complex rather than with chaperones alone, in line with the release of the chaperones in the bacterial cytoplasm after the dissociation from their exported proteins. Moreover, we suggest a new role of the gate-keeper complex and the ATPase in the regulation of early substrates recognition by the T3SS. This finding sheds a new light on the mechanism of secretion switching from early to middle substrates in P. aeruginosa.

中文翻译：

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PopN Gate-keeper复合物作用于ATPase PscN，以调节铜绿假单胞菌从早期到中间底物的T3SS分泌转换

铜绿假单胞菌是一种机会细菌，其主要毒力因子是III型分泌系统。该机制的ATPase PscN（SctN）被认为位于分泌设备的底部，并参与识别，伴侣解离和展开输出的T3SS蛋白。在这项工作中，蛋白质-蛋白质相互作用ELISA显示了PscN与多种输出的T3SS蛋白质的相互作用，包括针，转运蛋白，门卫和效应子。这些相互作用进一步被微尺度热电泳证实了，这也表明PscN与分泌的蛋白或蛋白-伴侣复合物而不是单独与伴侣具有优先相互作用，这与伴侣从其输出蛋白解离后在细菌细胞质中的释放有关。此外，我们建议门卫复合物和ATPase在调节T3SS早期底物识别的新作用。这一发现为分泌物从早期底物转变为中间底物提供了新的思路。铜绿假单胞菌。