Hueck C J, Hantman M J, Bajaj V, Johnston C, Lee C A, Miller S I
Department of Infectious Diseases and Microbiology, University of Washington, Seattle 98195, USA.
Mol Microbiol. 1995 Nov;18(3):479-90. doi: 10.1111/j.1365-2958.1995.mmi_18030479.x.
Salmonella typhimurium secreted proteins (Ssp) were previously implicated in epithelial cell invasion. Here we describe four genes (SspB, sspC, sspD, and sspA), located between spaT and prgH, which encode proteins of 63, 42, 36, and 87 kDa, respectively. These Ssp are homologous to Shigella flexneri secreted proteins IpaB, IpaC, IpaD and IpaA. A non-invasive mutant with a transposon insertion in sspC lacks Ssp of 87, 42 and 36 kDa. Complementation and analyses show that sspC and sspD encode the 42 and the 36 kDa Ssp, while the 87 kDa Ssp is encoded by sspA. sspC and sspD, but not sspA, are required for invasion. Amino-terminal sequencing shows that SspC and SspA are secreted without amino-terminal processing. We further demonstrate that Ssp secretion requires proteins encoded by prgHIJK, homologous to the Shigella Ipa secretion system, since SspA is abundantly secreted by wild-type bacteria but is completely retained within the cellular fraction of a prgHIJK mutant. A precipitate containing abundant SspC and three other major Ssp of 63, 59 and 22 kDa was isolated from culture supernatants of wild-type bacteria. These data indicate that major secreted invasion determinants of S. typhimurium are structurally and functionally homolgous to S. flexneri Ipa proteins.
鼠伤寒沙门氏菌分泌蛋白（Ssp）先前被认为与上皮细胞侵袭有关。在此我们描述了位于spaT和prgH之间的四个基因（SspB、sspC、sspD和sspA），它们分别编码63 kDa、42 kDa、36 kDa和87 kDa的蛋白质。这些Ssp与弗氏志贺氏菌分泌蛋白IpaB、IpaC、IpaD和IpaA同源。在sspC中插入转座子的非侵袭性突变体缺乏87 kDa、42 kDa和36 kDa的Ssp。互补和分析表明，sspC和sspD编码42 kDa和36 kDa的Ssp，而87 kDa的Ssp由sspA编码。侵袭需要sspC和sspD，但不需要sspA。氨基末端测序表明，SspC和SspA在没有氨基末端加工的情况下被分泌。我们进一步证明，Ssp分泌需要由prgHIJK编码的蛋白质，它们与志贺氏菌Ipa分泌系统同源，因为SspA由野生型细菌大量分泌，但完全保留在prgHIJK突变体的细胞部分内。从野生型细菌的培养上清液中分离出一种含有丰富SspC和其他三种主要Ssp（63 kDa、59 kDa和22 kDa）的沉淀物。这些数据表明，鼠伤寒沙门氏菌主要的分泌性侵袭决定因素在结构和功能上与弗氏志贺氏菌Ipa蛋白同源。
