Department of Cell Biology, Duke University Medical Center, Durham, NC 27710-3709, USA.
Proc Natl Acad Sci U S A. 2013 Jul 2;110(27):11000-4. doi: 10.1073/pnas.1222254110. Epub 2013 Jun 17.
We previously reconstituted Z rings in tubular multilamellar liposomes with FtsZ-YFP-mts, where mts is a membrane-targeting amphiphilic helix. These reconstituted Z rings generated a constriction force but did not divide the thick-walled liposomes. Here we developed a unique system to observe Z rings in unilamellar liposomes. FtsZ-YFP-mts incorporated inside large, unilamellar liposomes formed patches that produced concave distortions when viewed at the equator of the liposome. When viewed en face at the top of the liposome, many of the patches were seen to be small Z rings, which still maintained the concave depressions. We also succeeded in reconstituting the more natural, two-protein system, with FtsA and FtsZ-YFP (having the FtsA-binding peptide instead of the mts). Unilamellar liposomes incorporating FtsA and FtsZ-YFP showed a variety of distributions, including foci and linear arrays. A small fraction of liposomes had obvious Z rings. These Z rings could constrict the liposomes and in some cases appeared to complete the division, leaving a clear septum between the two daughter liposomes. Because complete liposome divisions were not seen with FtsZ-mts, FtsA may be critical for the final membrane scission event. We demonstrate that reconstituted cell division machinery apparently divides the liposome in vitro.
我们之前曾在含有 FtsZ-YFP-mts 的管状多层脂质体中重建 Z 环,其中 mts 是一种靶向膜的两亲性螺旋。这些重建的 Z 环产生了收缩力,但没有将厚壁脂质体分开。在这里,我们开发了一种独特的系统来观察单层脂质体中的 Z 环。FtsZ-YFP-mts 被包裹在大的单层脂质体内部,形成斑块,当从脂质体的赤道处观察时,这些斑块会产生凹面变形。当从脂质体顶部正面观察时,许多斑块被视为小的 Z 环,这些 Z 环仍然保持着凹面凹陷。我们还成功地重建了更自然的双蛋白系统,其中含有 FtsA 和 FtsZ-YFP(具有 FtsA 结合肽而不是 mts)。包含 FtsA 和 FtsZ-YFP 的单层脂质体显示出多种分布,包括焦点和线性阵列。一小部分脂质体有明显的 Z 环。这些 Z 环可以收缩脂质体,在某些情况下似乎完成了分裂,在两个子脂质体之间留下一个清晰的隔膜。由于没有观察到 FtsZ-mts 的完整脂质体分裂,FtsA 可能对最终的膜分裂事件至关重要。我们证明,体外重建的细胞分裂机制显然可以将脂质体分开。