Single molecules of the bacterial actin MreB undergo directed treadmilling motion in Caulobacter crescentus
Single molecules of the bacterial actin MreB undergo directed treadmilling motion in Caulobacter crescentus
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DOI：
10.1073/pnas.0604503103
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发表时间：
2006-07-18
影响因子：
11.1
通讯作者：
Moerner, W. E.
中科院分区：
文献类型：
--
作者：
Kim, So Yeon;Gitai, Zemer;Moerner, W. E.
肌动蛋白细胞骨架代表了真核生物和原核生物中多种基本细胞功能的关键调节因子。在真核生物中，这些功能依赖于肌动蛋白丝组装和拆卸的协调动力学。然而，细菌肌动蛋白同源物MreB的动力学尚未在体内进行研究。在这项研究中，我们观察了运动的单荧光MreB-黄色荧光蛋白融合在活的柄杆菌细胞中的背景下的未标记的MreB。通过延时成像，可以区分聚合的MreB [丝状MreB（fMreB）]和未聚合的MreB [球状MreB（gMreB）]单体：gMreB显示快速运动，这是布朗扩散的特征，而fMreB中的标记分子显示缓慢的定向运动。标记的MreB在生长的聚合物中的这种定向运动提供了一个指示，即像肌动蛋白一样，MreB单体通过在一个细丝末端的优先聚合和在另一个细丝末端的解聚而跑步通过MreB细丝。从这些数据中，我们提取了单个MreB细丝的几个特征，包括它们平均比细胞长度短得多，并且它们的极化组装的方向似乎与整体细胞极性无关。因此，像肌动蛋白一样，MreB在体内表现出螺旋铣削行为，并且在多种细菌物种中观察到的长MreB结构似乎代表缺乏统一全局极性的短细丝束。
The actin cytoskeleton represents a key regulator of multiple essential cellular functions in both eukaryotes and prokaryotes. In eukaryotes, these functions depend on the orchestrated dynamics of actin filament assembly and disassembly. However, the dynamics of the bacterial actin homolog MreB have yet to be examined in vivo. In this study, we observed the motion of single fluorescent MreB-yellow fluorescent protein fusions in living Caulobacter cells in a background of unlabeled MreB. With time-lapse imaging, polymerized MreB [filamentous MreB (fMreB)] and unpolymerized MreB [globular MreB (gMreB)] monomers could be distinguished: gMreB showed fast motion that was characteristic of Brownian diffusion, whereas the labeled molecules in fMreB displayed slow, directed motion. This directional movement of labeled MreB in the growing polymer provides an indication that, like actin, MreB monomers treadmill through MreB filaments by preferential polymerization at one filament end and depolymerization at the other filament end. From these data, we extract several characteristics of single MreB filaments, including that they are, on average, much shorter than the cell length and that the direction of their polarized assembly seems to be independent of the overall cellular polarity. Thus, MreB, like actin, exhibits treadmilling behavior in vivo, and the long MreB structures that have been visualized in multiple bacterial species seem to represent bundles of short filaments that lack a uniform global polarity.