Bacterial Cell Biology, Swammerdam Institute for Life Sciences, University of Amsterdam, 1098 XH Amsterdam, The Netherlands.
Molecular Biotechnology, Institute of Biology, Leiden University, 2333 BE, Leiden, The Netherlands.
Proc Natl Acad Sci U S A. 2021 Jan 12;118(2). doi: 10.1073/pnas.2002635118.
Gram-positive bacteria divide by forming a thick cross wall. How the thickness of this septal wall is controlled is unknown. In this type of bacteria, the key cell division protein FtsZ is anchored to the cell membrane by two proteins, FtsA and/or SepF. We have isolated SepF homologs from different bacterial species and found that they all polymerize into large protein rings with diameters varying from 19 to 44 nm. Interestingly, these values correlated well with the thickness of their septa. To test whether ring diameter determines septal thickness, we tried to construct different SepF chimeras with the purpose to manipulate the diameter of the SepF protein ring. This was indeed possible and confirmed that the conserved core domain of SepF regulates ring diameter. Importantly, when SepF chimeras with different diameters were expressed in the bacterial host , the thickness of its septa changed accordingly. These results strongly support a model in which septal thickness is controlled by curved molecular clamps formed by SepF polymers attached to the leading edge of nascent septa. This also implies that the intrinsic shape of a protein polymer can function as a mold to shape the cell wall.
革兰氏阳性菌通过形成一个厚厚的横膈膜来进行分裂。目前尚不清楚这个隔膜的厚度是如何控制的。在这类细菌中，关键的细胞分裂蛋白 FtsZ 通过两种蛋白质 FtsA 和/或 SepF 锚定在细胞膜上。我们从不同的细菌物种中分离出了 SepF 同源物，发现它们都聚合成直径在 19 到 44nm 之间的大型蛋白质环。有趣的是，这些值与它们隔膜的厚度很好地相关。为了测试环的直径是否决定隔膜的厚度，我们试图构建不同的 SepF 嵌合体，目的是操纵 SepF 蛋白环的直径。这确实是可能的，并证实了 SepF 的保守核心结构域调节环的直径。重要的是，当具有不同直径的 SepF 嵌合体在细菌宿主中表达时，其隔膜的厚度相应地发生变化。这些结果强烈支持了这样一种模型，即隔膜的厚度是由附着在新形成的隔膜前缘的 SepF 聚合物形成的弯曲分子夹来控制的。这也意味着蛋白质聚合物的固有形状可以作为一种模具来塑造细胞壁。
