Abstract
The placement of cell division site in model bacteria E.coli is tightly regulated by Min system. In E. Coli, Min system blocks the polar position for cell division, MinC, D and E are three members in Min system. Among the Min system, MinE can form a ring-like structure (the MinE-ring) in E. coli and oscillates with MinCD. MinE includes 88 amino acids and contains three domains: the N-terminal membrane targeting domain (MinE2-12), the anti-MinCD domain (MinE13-31) and the C-terminal dimerization domain (MinE32-88). In this study, we study the self-assembly behavior of MinE and MinE1-31 on mica and on supported lipid bilayer prepared from E-coli phospholipids extraction. To investigate the self-assembly behavior of MinE and MinE1-31, we utilize highly sensitive Frequency Modulation Atomic Force Microscopy (FM-AFM). FM-AFM applies a small force over the surface, thereby causes little deformation on soft and fragile biological samples. The results indicated that the features of both MinE and MinE1-31 filaments on supported lipid bilayer were very different from those assembling on mica. On mica, N-terminal MinE1-31 fragments self-assembled into filamentous bundles that contained 4~6 prorofilaments. However, the number of protofilament within filamentous bundles varied when appiled MinE1-31 on support lipid bilayer. For full length MinE, although the self-assembled structure shown on mica is amorphous, MinE was able to arrange into short protein filaments that decorated around edges of the membrane patches. We can conclude that MinEexhibits spatial preference to membrane edge but MinE1-31 does not. The results also hint that C-terminal MinE plays the main role in MinE membrane edge binding activity. Thesefindings may be cruicial to the MinE-ring formation in the midcell.