Dynamic localization cycle of the cell division regulator MinE in Escherichia coli

The MinC protein directs placement of the division septum to the middle of Escherichia coli cells by blocking assembly of the division apparatus at ot her sites. MinD and MinE regulate MinC activity by modulating its cellular location in a unique fashion. MinD recruits MinC to the membrane, and MinE induces MinC/MinD to oscillate rapidly between the membrane of opposite cel l halves. Using fixed cells, we previously found that a MinE-green fluoresc ent protein fusion accumulated in an annular structure at or near the midce ll, as well as along the membrane on only one side of the ring. Here we sho w that in living cells, MinE undergoes a rapid localization cycle that appe ars coupled to MinD oscillation. The results show that MinE is not a fixed marker for septal ring assembly. Rather, they support a model in which MinE stimulates the removal of MinD from the membrane in a wave-like fashion. T hese waves run from a midcell position towards the poles in an alternating sequence such that the time-averaged concentration of division inhibitor is lowest at midcell.