Institut für Theoretische Physik, Technische Universität Berlin, Hardenbergstr. 36, D-10623 Berlin, Germany.
Phys Biol. 2011 Aug;8(4):046009. doi: 10.1088/1478-3975/8/4/046009. Epub 2011 Jul 20.
Bacteria such as Escherichia coli propel themselves by rotating a bundle of helical filaments, each driven by a rotary motor embedded in the cell membrane. Each filament is an assembly of thousands of copies of the protein flagellin which assumes two different states. We model the filament by an elastic network of rigid bodies that form bonds with one another according to a scheme suggested by Namba and Vondervistz (1997 Q. Rev. Biophys. 30 1-65) and add additional binding sites at the inner part of the rigid body. Our model reproduces the helical parameters of the 12 possible polymorphic configurations very well. We demonstrate that its energetical ground state corresponds to the normal helical form, usually observed in nature, only when inner and outer binding sites of the rigid body have a large axial displacement. This finding correlates directly to the elongated shape of the flagellin molecule. An Ising Hamiltonian in our model directly addresses the two states of the flagellin protein. It contains an external field that represents external parameters which allow us to alter the ground state of the filament.
细菌（如大肠杆菌）通过旋转一束螺旋丝来推动自身，每个螺旋丝都由嵌入细胞膜中的旋转电机驱动。每个细丝由数千个鞭毛蛋白组成，这些蛋白有两种不同的状态。我们通过一个刚性体的弹性网络来模拟细丝，这些刚性体根据 Namba 和 Vondervistz（1997 年 Q. Rev. Biophys. 30 1-65）提出的方案相互形成键，并在刚性体的内部添加额外的结合位点。我们的模型很好地再现了 12 种可能的多晶型构象的螺旋参数。我们证明，只有当刚性体的内外结合位点有较大的轴向位移时，其能量基态才对应于通常在自然界中观察到的正常螺旋形式。这一发现与鞭毛蛋白分子的伸长形状直接相关。我们模型中的伊辛哈密顿量直接处理鞭毛蛋白的两种状态。它包含一个外部场，代表允许我们改变细丝基态的外部参数。
