A channel connecting the mother cell and forespore during bacterial endospore formation
A channel connecting the mother cell and forespore during bacterial endospore formation
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DOI：
10.1073/pnas.0806301105
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发表时间：
2008-09-30
影响因子：
11.1
通讯作者：
Moran, Charles P., Jr.
中科院分区：
文献类型：
--
作者：
Meisner, Jeffrey;Wang, Xin;Moran, Charles P., Jr.
在枯草芽孢杆菌孢子内发育的早期阶段，细菌不对称分裂产生两个子细胞。较小的细胞（前孢子）分化为内孢子，较大的细胞（母细胞）分化为终末分化细胞，培养发育中的前孢子。在发育过程中，母细胞吞噬前孢子产生原生质体，原生质体被两层双层膜包围，将其与母细胞的细胞质分开。在前孢子被吞噬后，驱动前孢子晚期基因表达的sigma(G)的激活需要在母细胞中表达spoIIIA位点。其中一种由spoiia编码的蛋白SpoIIIAH通过其c端胞外结构域与前孢子膜蛋白SpoIIQ的c端胞外结构域的相互作用，特异性靶向前孢子周围的膜。我们发现了SpoIIIAH的c端结构域与YscJ/FliF蛋白家族之间的同源关系，YscJ/FliF蛋白家族的成员形成多聚环，参与III型分泌系统和鞭毛。如果SpoIIIAH形成类似的环状结构，它也可能在母细胞和前孢子膜之间形成通道。为了验证这一假设，我们开发了一种区隔化生物素化实验，我们用它来证明SpoIIIAH的c端胞外结构域可以通过前孢子细胞质进行酶修饰。这些结果和其他结果使我们认为，SpoIIIAH形成了前孢子和母细胞之间通道的一部分，这是激活sigma(G)所必需的。
At an early stage during Bacillus subtilis endospore development the bacterium divides asymmetrically to produce two daughter cells. The smaller cell (forespore) differentiates into the endospore, while the larger cell (mother cell) becomes a terminally differentiated cell that nurtures the developing forespore. During development the mother cell engulfs the forespore to produce a protoplast, surrounded by two bilayer membranes, which separate it from the cytoplasm of the mother cell. The activation of sigma(G), which drives late gene expression in the forespore, follows forespore engulfment and requires expression of the spoIIIA locus in the mother cell. One of the spoIIIA-encoded proteins SpoIIIAH is targeted specifically to the membrane surrounding the forespore, through an interaction of its C-terminal extracellular domain with the C-terminal extracellular domain of the forespore membrane protein SpoIIQ. We identified a homologous relationship between the C-terminal domain of SpoIIIAH and the YscJ/FliF protein family, members of which form multimeric rings involved in type III secretion systems and flagella. If SpoIIIAH forms a similar ring structure, it may also form a channel between the mother cell and forespore membranes. To test this hypothesis we developed a compartmentalized biotinylation assay, which we used to show that the C-terminal extracellular domain of SpoIIIAH is accessible to enzymatic modification from the forespore cytoplasm. These and other results lead us to suggest that SpoIIIAH forms part of a channel between the forespore and mother cell that is required for the activation of sigma(G) .