Fedorov O V, Kostyukova A S
FEBS Lett. 1984 Jun 4;171(1):145-8. doi: 10.1016/0014-5793(84)80476-7.
The chemotaxis of bacteria such as Salmonella and Escherichia coli involves smooth swimming punctuated by periods of tumbling. In smooth swimming the flagellar filaments are left-handed, in tumbling they are right-handed with a different wavelength. The filaments are constructed from a globular protein, flagellin, by a process of self-assembly. The existing models assume that the flagellin molecule is bistable and longitudinal rows of subunits take one of the two possible conformations. Such a model explains the observed different morphology of the flagellum. We have studied Salmonella and E. coli flagellins in polymeric and monomeric forms by scanning microcalorimetry and circular dichroism. We have inferred that a flagellin molecule consists of several domains, two of which are structured at physiological temperatures and are in the monomeric form, while the others acquire a regular form only in the process of polymerization. This phenomenon may be the basis of a process during which the flagellin molecule, fitting into the flagellum, acquires a conformation analogous to that of the neighbouring molecule in the longitudinal row.
沙门氏菌和大肠杆菌等细菌的趋化作用涉及平稳游动，并伴有翻滚期。在平稳游动时，鞭毛丝呈左旋，在翻滚时则呈右旋且波长不同。鞭毛丝由一种球状蛋白质鞭毛蛋白通过自组装过程构建而成。现有的模型假定鞭毛蛋白分子是双稳态的，纵向排列的亚基采取两种可能构象中的一种。这样的模型解释了所观察到的鞭毛不同形态。我们通过扫描量热法和圆二色性研究了聚合态和单体态的沙门氏菌和大肠杆菌鞭毛蛋白。我们推断，一个鞭毛蛋白分子由几个结构域组成，其中两个在生理温度下具有结构且呈单体形式，而其他结构域仅在聚合过程中才形成规则形式。这种现象可能是鞭毛蛋白分子装配到鞭毛中时获得与纵向排列中相邻分子类似构象这一过程的基础。
