Functional characterization of type III secretion apparatus STM1410 encoded by Salmonella pathogenicity island 2

许多革兰氏阴性病原体的毒力与III型分泌系统（T3 SS）相关，其将毒力效应蛋白递送到宿主细胞的细胞质中。沙门氏菌T3 SS的组分在沙门氏菌致病岛I和II（SPI-1和SPI-2）内编码。虽然沙门氏菌中的大多数SPI-2 T3 SS蛋白质都有指定的名称和功能，但其中一些蛋白质的特征仍然很差。在这里，我们研究了SPI-2编码的蛋白质，STM 1410，它与其他T3 SS/鞭毛蛋白没有同源性，只存在于致病性沙门氏菌中。我们的研究结果表明，它是必不可少的III型分泌，它是本地化的内膜。有趣的是，我们发现STM 1410对于SPI-2效应蛋白Pip B的稳定性至关重要。总之，我们的研究结果表明，STM 1410是一种结构蛋白，有助于T3 S复合物的功能，因此我们建议将其重命名为Ssa W。

The virulence of many Gram-negative pathogens is associated with type III secretion systems(T3SSs), which deliver virulence effector proteins into the cytoplasm of host cells. Components of Salmonella T3SS are encoded within Salmonella pathogenicity island I and II(SPI-1 and SPI-2). While most SPI-2 T3SS proteins in Salmonella have assigned names and functions, a few of them remain poorly characterized. Here, we studied a SPI-2-encoded protein, STM1410, that shows no homology to other T3SS/flagellar proteins and is only present in pathogenic Salmonella. Our findings demonstrated that it is essential for type III secretion and that it is localized to the inner membrane. Interestingly, we found STM1410 is critical for the stability for the SPI-2 effector protein Pip B. Overall, our findings suggest that STM1410 is a structural protein that contributes to the function of the T3S complex, and therefore we propose to rename it Ssa W.