Mikrobiologie, Fachbereich für Biologie, University of Freiburg, Schänzlestraße 1, Freiburg 79104, Germany.
BMC Microbiol. 2012 Dec 19;12:298. doi: 10.1186/1471-2180-12-298.
In eukaryotic cells, dynamin and flotillin are involved in processes such as endocytosis and lipid raft formation, respectively. Dynamin is a GTPase that exerts motor-like activity during the pinching off of vesicles, while flotillins are coiled coil rich membrane proteins with no known enzymatic activity. Bacteria also possess orthologs of both classes of proteins, but their function has been unclear.
We show that deletion of the single dynA or floT genes lead to no phenotype or a mild defect in septum formation in the case of the dynA gene, while dynA floT double mutant cells were highly elongated and irregularly shaped, although the MreB cytoskeleton appeared to be normal. DynA colocalizes with FtsZ, and the dynA deletion strain shows aberrant FtsZ rings in a subpopulation of cells. The mild division defect of the dynA deletion is exacerbated by an additional deletion in ezrA, which affects FtsZ ring formation, and also by the deletion of a late division gene (divIB), indicating that DynA affects several steps in cell division. DynA and mreB deletions generated a synthetic defect in cell shape maintenance, showing that MreB and DynA play non-epistatic functions in cell shape maintenance. TIRF microscopy revealed that FloT forms many dynamic membrane assemblies that frequently colocalize with the division septum. The deletion of dynA did not change the pattern of localization of FloT, and vice versa, showing that the two proteins play non redundant roles in a variety of cellular processes. Expression of dynamin or flotillin T in eukaryotic S2 cells revealed that both proteins assemble at the cell membrane. While FloT formed patch structures, DynA built up tubulated structures extending away from the cells.
Bacillus subtilis dynamin ortholog DynA plays a role during cell division and in cell shape maintenance. It shows a genetic link with flotillin T, with both proteins playing non-redundant functions at the cell membrane, where they assemble even in the absence of any bacterial cofactor.
在真核细胞中，dynamin 和 flotillin 分别参与胞吞作用和脂筏形成等过程。dynamin 是一种 GTPase，在囊泡缢缩过程中发挥马达样活性，而 flotillin 是富含卷曲螺旋的膜蛋白，没有已知的酶活性。细菌也具有这两类蛋白的同源物，但它们的功能尚不清楚。
我们发现，dynA 或 floT 单个基因的缺失不会导致表型或 septum 形成的轻微缺陷，但 dynA floT 双突变体细胞高度伸长且形状不规则，尽管 MreB 细胞骨架似乎正常。DynA 与 FtsZ 共定位，dynA 缺失株的部分细胞中出现异常的 FtsZ 环。dynA 缺失的轻微分裂缺陷因 ezrA 的额外缺失而加剧，ezrA 影响 FtsZ 环的形成，也因晚期分裂基因（divIB）的缺失而加剧，表明 DynA 影响细胞分裂的多个步骤。DynA 和 mreB 的缺失导致细胞形状维持的合成缺陷，表明 MreB 和 DynA 在细胞形状维持中发挥非上位性功能。TIRF 显微镜显示，FloT 形成许多动态膜组装体，这些膜组装体经常与分裂隔膜共定位。dynA 的缺失并没有改变 FloT 的定位模式，反之亦然，表明这两种蛋白质在多种细胞过程中发挥非冗余作用。真核 S2 细胞中 dynamin 或 flotillin T 的表达显示，这两种蛋白质都在细胞膜上组装。虽然 FloT 形成斑状结构，但 DynA 构建了从细胞延伸的管状结构。
枯草芽孢杆菌 dynamin 同源物 DynA 在细胞分裂和细胞形状维持中发挥作用。它与 flotillin T 存在遗传联系，这两种蛋白质在细胞膜上发挥非冗余功能，即使没有任何细菌辅因子，它们也能在细胞膜上组装。
