The N-Terminal Amphipathic Helix of the Topological Specificity Factor MinE Is Associated with Shaping Membrane Curvature

Pole-to-pole oscillations of the Min proteins in Escherichia coli are required for the proper placement of the division septum. Direct interaction of MinE with the cell membrane is critical for the dynamic behavior of the Min system. In vitro, this MinE-membrane interaction led to membrane deformation; however, the underlying mechanism remained unclear. Here we report that MinE-induced membrane deformation involves the formation of an amphipathic helix of MinE2–9, which, together with the adjacent basic residues, function as membrane anchors. Biochemical evidence suggested that the membrane association induces formation of the helix, with the helical face, consisting of A2, L3, and F6, inserted into the membrane. Insertion of this helix into the cell membrane can influence local membrane curvature and lead to drastic changes in membrane topology. Accordingly, MinE showed characteristic features of protein-induced membrane tubulation and lipid clustering in in vitro reconstituted systems. In conclusion, MinE shares common protein signatures with a group of membrane trafficking proteins in eukaryotic cells. These MinE signatures appear to affect membrane curvature.大肠杆菌（Escherichia coli）内的Min蛋白极间振荡，是细胞分裂隔膜正确定位所必需的。MinE与细胞膜的直接相互作用，对于Min系统的动态行为至关重要。体外实验中，这类MinE-膜相互作用可引发膜形变，但其背后的分子机制仍未明确。本研究发现，MinE诱导的膜形变涉及MinE2-9片段两亲性螺旋的形成，该螺旋与相邻的碱性残基共同作为膜锚定区域。生化证据表明，膜结合作用会诱导该螺旋的形成，其中由A2、L3和F6组成的螺旋面插入膜内。该螺旋插入细胞膜可影响局部膜曲率，并引发膜拓扑结构的剧烈改变。据此，MinE在体外重构系统中表现出蛋白质诱导的膜管形成与脂质聚集的典型特征。综上，MinE与真核细胞内一类膜转运蛋白共享共同的蛋白质特征序列，这些MinE特征序列似乎可调控膜曲率。