MOLECULAR BASIS OF BACTERIAL MOTILITY

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 许多类型的细菌使用被称为鞭毛的鞭状结构推动它们自己通过液体培养基（http：//www.ks.uiuc.edu/Research/flagellum/）。 细菌的鞭毛是一个巨大的（几微米长，20纳米宽），多蛋白组装体由三个结构域组成：一个基体，作为马达;一个钩，作为关节;和一根细丝，它构成了鞭毛的大部分长度，并与溶剂相互作用以推动细菌。 根据基体施加的扭矩的方向，细丝呈现不同的螺旋形状。 在逆时针旋转（从细胞外部观察）下，几个鞭毛形成单个螺旋束，其沿沿着直线推动细胞，称为运行模式[1]。在顺时针旋转下，单个鞭毛从束中分离并形成单独的右手螺旋，导致细胞翻滚。通过改变奔跑和翻滚的持续时间，细菌可以通过有偏随机游走沿着引诱剂或驱避剂的梯度向上或向下移动。 关于鞭毛的一个尚未解决的问题是，马达施加的反向扭矩如何导致丝状体螺旋形状之间的切换。 这种转换是细丝中多态性转变的结果，当单个蛋白质单元相互滑动时[2]，但尽管进行了大量的实验工作[3，2，4]和最近的计算研究[5]，但其分子机制仍然知之甚少。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Many types of bacteria propel themselves through liquid media using whip-like structures known as flagella (http://www.ks.uiuc.edu/Research/flagellum/). The bacterial flagellum is a huge (several micrometers long, 20 nm wide), multiprotein assembly built of three domains: a basal body, acting as a motor; a hook, acting as a joint; and a filament, which makes up the bulk of the length of the flagellum and interacts with solvent to propel the bacterium. Depending on the direction of the torque applied by the basal body, the filament assumes different helical shapes. Under counter-clockwise rotation (as viewed from the exterior of the cell), several flagella form a single helical bundle which propels the cell along a straight line, referred to as running mode [1]. Under clockwise rotation, the individual flagella dissociate from the bundle and form separate right-handed helices, causing the cell to tumble. Varying the duration of running and tumbling, bacteria can move up or down a gradient of an attractant or repellent by a biased random walk. One of the unresolved questions about the flagellum is how the reversal of torque applied by the motor results in a switching between the helical shapes of the filament. This switching is a result of polymorphic transitions in the filament, when individual protein units slide against each other [2], but its molecular mechanism remains poorly understood despite extensive experimental work [3, 2, 4] and a recent computational study [5].