Cytoskeletal "jellyfish" structure of Mycoplasma mobile
Cytoskeletal "jellyfish" structure of Mycoplasma mobile
复制标题
DOI：
10.1073/pnas.0704280104
复制
发表时间：
2007-12-04
影响因子：
11.1
通讯作者：
Miyata, Makoto
中科院分区：
文献类型：
--
作者：
Nakane, Daisuke;Miyata, Makoto
移动支原体是一种缺乏肽聚糖层的寄生细菌，它通过一种独特的机制在固体表面上沿着细胞极膜突起的方向滑动。最近，我们提出了一种工作模型，在该模型中，细胞由聚集在突起底部的腿蛋白推动。腿在固体表面反复捕捉和释放唾液酸，这一运动是由ATP水解产生的力驱动的。在这里，为了阐明支持滑翔力和细胞形状的亚细胞结构，我们用Triton X-100剥离了细胞膜，并鉴定了一种独特的结构，将其命名为“水母”结构。在这种结构中，一个宽约235 nm，长约155 nm的椭圆形固体“钟形”填充了一个12 nm的六方晶格，并与该结构相连的是数十个柔性的“触角”，这些触角以大约30 nm的间隔覆盖着直径为20 nm的颗粒。这些粒子似乎有180个旋转对称性，中心有一个酒窝。这种结构与滑动机制的关系是通过它的细胞定位和对缺乏滑动所必需蛋白质的突变体的分析而提出的。我们通过质谱学鉴定了10个蛋白质组分，发现这些蛋白质与细菌细胞骨架的其他蛋白质或先前鉴定的滑动蛋白质没有序列相似性。免疫荧光和免疫电子显微镜显示，两种成分定位于钟状，另一种结构类似于F-1-ATPaseβ亚基的成分定位于触须。
Mycoplasma mobile, a parasitic bacterium lacking a peptidoglycan layer, glides on solid surfaces in the direction of a membrane protrusion at a cell pole by a unique mechanism. Recently, we proposed a working model in which cells are propelled by leg proteins clustering at the protrusion's base. The legs repeatedly catch and release sialic acids on the solid surface, a motion that is driven by the force generated by ATP hydrolysis. Here, to clarify the subcellular structure supporting the gliding force and the cell shape, we stripped the membrane by Triton X-100 and identified a unique structure, designated the "jellyfish" structure. In this structure, an oval solid "bell" approximate to 235 wide and 155 nm long is filled with a 12-nm hexagonal lattice and connected to this structure are dozens of flexible "tentacles" that are covered with particles of 20-nm diameter at intervals of approximate to 30 nm. The particles appear to have 180 rotational symmetry and a dimple at the center. The relation of this structure to the gliding mechanism was suggested by its cellular localization and by analyses of mutants lacking proteins essential for gliding. We identified 10 proteins as the components by mass spectrometry and found that these do not show sequence similarities with other proteins of bacterial cytoskeletons or the gliding proteins previously identified. Immunofluorescence and immunoelectron microscopy revealed that two components are localized at the bell and another that has the structure similar to the F-1-ATPase beta subunit is localized at the tentacles.