Periplasmic transit and disulfide bond formation of the autotransported Shigella protein IcsA
Periplasmic transit and disulfide bond formation of the autotransported Shigella protein IcsA
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DOI：
10.1128/jb.183.3.951-958.2001
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发表时间：
2001-02-01
影响因子：
3.2
通讯作者：
Goldberg, MB
中科院分区：
文献类型：
--
作者：
Brandon, LD;Goldberg, MB
志贺氏菌外膜蛋白 IcsA 属于 V 型分泌（自转运）毒力因子家族。该家族的成员介导其自身跨细菌外膜的易位：羧基端 β 结构域在外膜中形成 β 桶通道，氨基端 OL 结构域通过该通道。 IcsA 位于细菌的一极，介导志贺氏菌的肌动蛋白组装，这对于细菌的细胞内运动和细胞间传播至关重要。在这里，我们描述了 IcsA 在分泌过程中穿过周质的转运。我们发现，dsbB 基因中的插入（其基因产物介导许多周质中间体的二硫键形成）不会影响 IcsA 的表面表达或单极靶向。然而，IcsA 以 DsbA/DsbB 依赖性方式在周质中形成一个二硫键。此外，细胞分级分离研究表明 IcsA 具有瞬时可溶性周质中间体。我们的数据还表明，IcsA 在周质中以蛋白酶 K 抗性状态折叠。根据这些数据，我们提出了一种新的 IcsA 分泌模型，该模型可能适用于其他自转运蛋白。
The Shigella outer membrane protein IcsA belongs to the family of type V secreted (autotransported) virulence factors. Members of this family mediate their own translocation across the bacterial outer membrane: the carboxy-terminal beta domain forms a beta barrel channel in the outer membrane through which the amino-terminal OL domain passes. IcsA, which is localized at one pole of the bacterium, mediates actin assembly by Shigella, which is essential for bacterial intracellular movement and intercellular dissemination. Here, we characterize the transit of IcsA across the periplasm during its secretion. We show that an insertion in the dsbB gene, whose gene product mediates disulfide bond formation of many periplasmic intermediates, does not affect the surface expression or unipolar targeting of IcsA. However, IcsA forms one disulfide bond in the periplasm in a DsbA/DsbB-dependent fashion. Furthermore, cellular fractionation studies reveal that IcsA has a transient soluble periplasmic intermediate. Our data also suggest that IcsA is folded in a proteinase K-resistant state in the periplasm, From these data, we propose a novel model for the secretion of IcsA that may be applicable to other autotransported proteins.