Evidence that the SpoIIIE DNA translocase participates in membrane fusion during cytokinesis and engulfment
Evidence that the SpoIIIE DNA translocase participates in membrane fusion during cytokinesis and engulfment
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DOI：
10.1111/j.1365-2958.2005.05004.x
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发表时间：
2006-02-01
影响因子：
3.6
通讯作者：
Pogliano, K
中科院分区：
文献类型：
--
作者：
Liu, NJL;Dutton, RJ;Pogliano, K
在枯草芽孢杆菌孢子形成过程中，SpoIIIE是被困前孢子染色体穿过孢子形成隔膜的易位、细胞特异性基因表达的区室化以及吞噬后的膜融合所必需的。我们分离了SpoIIIE膜结构域中阻断定位和功能的突变。一种突变蛋白最初正常定位并完成DNA易位，但在吞噬后显示减少的膜融合。光漂白实验后的荧光恢复表明，在这个突变体的孢子形成隔膜保持开放，允许胞质内容物扩散之间的子细胞，这表明它阻止胞质分裂后，以及吞噬后的膜融合。我们建议，SpoIIIE催化这些拓扑结构相反的融合事件组装或拆卸蛋白质融合孔。SpoIIIE装配缺陷的突变体也证明SpoIIIE提供扩散屏障的能力与其在DNA易位期间在隔膜中点处装配焦点的能力成正比。因此，SpoIIIE通过两种不同的机制介导区室化：SpoIIIE焦点首先在DNA易位期间提供暂时的扩散屏障，然后介导分裂后膜融合的完成以提供永久的扩散屏障。因此，SpoIIIE样蛋白可能有助于将胞质分裂的最后一步（隔膜融合）与染色体分离的完成结合起来。
During Bacillus subtilis sporulation, SpoIIIE is required for translocation of the trapped forespore chromosome across the sporulation septum, for compartmentalization of cell-specific gene expression, and for membrane fusion after engulfment. We isolated mutations within the SpoIIIE membrane domain that block localization and function. One mutant protein initially localizes normally and completes DNA translocation, but shows reduced membrane fusion after engulfment. Fluorescence recovery after photobleaching experiments demonstrate that in this mutant the sporulation septum remains open, allowing cytoplasmic contents to diffuse between daughter cells, suggesting that it blocks membrane fusion after cytokinesis as well as after engulfment. We propose that SpoIIIE catalyses these topologically opposite fusion events by assembling or disassembling a proteinaceous fusion pore. Mutants defective in SpoIIIE assembly also demonstrate that the ability of SpoIIIE to provide a diffusion barrier is directly proportional to its ability to assemble a focus at the septal midpoint during DNA translocation. Thus, SpoIIIE mediates compartmentalization by two distinct mechanisms: the SpoIIIE focus first provides a temporary diffusion barrier during DNA translocation, and then mediates the completion of membrane fusion after division to provide a permanent diffusion barrier. SpoIIIE-like proteins might therefore serve to couple the final step in cytokinesis, septal membrane fusion, to the completion of chromosome segregation.