Identification of a specific chaperone for SptP, a substrate of the centisome 63 type III secretion system of Salmonella typhimurium
Identification of a specific chaperone for SptP, a substrate of the centisome 63 type III secretion system of Salmonella typhimurium
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DOI：
10.1128/jb.180.13.3393-3399.1998
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发表时间：
1998-07-01
影响因子：
3.2
通讯作者：
Galán, JE
中科院分区：
文献类型：
--
作者：
Fu, YX;Galán, JE
鼠伤寒沙门氏菌使用在其染色体的第63个centisome编码的III型蛋白分泌系统将效应分子递送到宿主细胞中。这些蛋白质刺激宿主细胞反应，如肌动蛋白细胞骨架的重组和转录因子的激活。这些效应蛋白之一是SptP，一种酪氨酸磷酸酶，导致宿主细胞肌动蛋白细胞骨架的破坏。III型分泌系统的许多底物的特征性特征是它们与特异性细胞质伴侣的结合，这似乎是这些蛋白质分泌和/或易位到宿主细胞中所需的。我们在这里报告的识别SicP，13 kDa的酸性多肽编码的SPTP的上游。sicP功能缺失突变导致SptP水平急剧下降，但不影响SptP表达？表明SicP在转录后发挥作用。脉冲追踪实验表明，SicP的缺失导致SptP的降解增加。此外，我们还发现SicP与SptP直接结合，且结合位点位于酪氨酸磷酸酶残基15和100之间。
Salmonella typhimurium uses of a type III protein secretion system encoded at centisome 63 of its chromosome to deliver effector molecules into the host cell. These proteins stimulate host cell responses such as reorganization of the actin cytoskeleton and activation of transcription factors. One of these effector proteins is SptP, a tyrosine phosphatase that causes disruption of the host cell actin cytoskeleton. A characteristic feature of many substrates of type III secretion systems is their association with specific cytoplasmic chaperones which appears to be required for secretion and/or translocation of these proteins into the host cell. We report here the identification of SicP, a 13-kDa acidic polypeptide that is encoded immediately upstream of sptP. A loss-of function mutation in sicP resulted in drastically reduced levels of SptP hut did not affect sptP expression? indicating that SicP exerts its effect posttranscriptionally. Pulse-chase experiments demonstrated that the loss of SicP leads to increased degradation of SptP, In addition, we show that SicP binds to SptP directly and that the binding site is located between residues 15 and 100 of the tyrosine phosphatase, Taken together, these results indicate that SicP acts as a specific chaperone for SptP.