Reversing cells and oscillating motility proteins
Reversing cells and oscillating motility proteins
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DOI：
10.1039/b806640j
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发表时间：
2008-10-01
影响因子：
--
通讯作者：
Sogaard-Andersen, Lotte
中科院分区：
文献类型：
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作者：
Leonardy, Simone;Bulyha, Iryna;Sogaard-Andersen, Lotte
细菌黄色粘球菌的细胞根据其营养状态组织成两种类型的模式，即在营养物存在下细胞形成扩展菌落，并且在营养物不存在下细胞形成子实体。这两种模式的形成都取决于定向细胞运动，而定向细胞运动又取决于运动性的调节。M. xanthus细胞具有两个运动机器，IV型皮利和A-引擎，它们协同作用以产生相同方向的动力。周期性地，单个细胞逆转其运动方向。在反转期间，两个动力机器切换极性以产生相反方向的力。最近的证据表明，在分子水平上，反转涉及运动蛋白的极到极振荡。在反转之间，这些蛋白质定位于细胞两极以刺激运动性，并且与反转平行，它们在两极之间重新定位。对于分别是IV型皮利和A-引擎的一部分的两种蛋白质FrzS和RomR，直接证明了它们彼此独立但同步地振荡，因此，提供了两种运动机器独立但同步地切换极性的证据。蛋白质振荡由Frz化学感受信号转导系统调节和同步。运动系统的正确极性可能由MgIA蛋白建立，MgIA蛋白是小GTP酶的Ras/Rac/Rho超家族的成员。在这种情况下，MgIA建立了两个运动机器的正确极性，并且Frz诱导的同步极性切换保持了两个运动机器的正确极性。
Cells of the bacterium Myxococcus xanthus organize into two types of patterns depending on their nutritional status, i.e. in the presence of nutrients cells form spreading colonies and in the absence of nutrients cells form fruiting bodies. Formation of both patterns depends on directed cell movements, which, in turn, depend on regulation of motility. M. xanthus cells harbor two motility machines, type IV pili and the A-engine, which act synergistically to generate motive force in the same direction. Periodically, the individual cells reverse their direction of movement. During a reversal the two motility machines switch polarity to generate force in the opposite direction. Recent evidence shows that at the molecular level, reversals involve pole-to-pole oscillations of motility proteins. Between reversals, these proteins localize to the cell poles to stimulate motility and in parallel with a reversal they relocalize between the poles. For two proteins, FrzS and RomR, which are part of the type IV pili and A-engine, respectively, it was directly demonstrated that they oscillate independently of each other but in synchrony, thus, providing evidence that the two motility machines switch polarity independently but synchronously. Protein oscillations are regulated and synchronized by the Frz chemosensory signal transduction system. The correct polarity of the motility systems is likely established by the MgIA protein, which is a member of the Ras/Rac/Rho superfamily of small GTPases. In this scenario, MgIA establishes the correct polarity of the two motility machines and the Frz-induced synchronized polarity switching maintains the correct polarity of the two motility machines.