| In Escherichia coli the pole-to-pole oscillation of the MinC division inhibitor is required for proper placement of the division machinery. The membrane association/dissociation cycle of MinC is driven by the MinD ATPase and the MinE topological specificity factor, which themselves undergo a coupled oscillatory localization cycle. During this cycle, MinD and a portion of MinE assemble on the membrane along one cell half in a pattern resembling a test tube (the MinD/E tube), while another portion of MinE assembles at the rim of this tube forming a ring-like structure (E-ring).; To understand the biochemical mechanisms behind Min protein dynamics, we investigated the interactions of purified Min proteins with ATP and phospholipid vesicles. We found that the ATP-bound form of MinD binds phospholipid vesicles in a cooperative fashion and recruits both MinC and MinE to the vesicles. In addition, we found that MinE stimulates the dissociation of MinC, MinD, and itself from the vesicles. Thus, ATP and MinE play critical roles in regulating the association and dissociation, respectively, of the Min proteins and the membrane.; MinE has two known functional domains: the N-terminal anti-MinCD domain (DMinE) and the C-terminal topological specificity and dimerization domain (TSMinE). We investigated the contributions of each domain of MinE in the regulation of Min protein-membrane dissociation. We found that DMinE is necessary and sufficient to stimulate dissociation of the Min proteins from the membrane. However, TSMinE is required to establish Min protein oscillation in a majority of cells. In addition, TSMinE is also required for E-ring formation. These results suggest that TSMinE and perhaps E-ring formation play a critical role in Min protein oscillation by helping to initiate and/or sustain Min protein dynamics.; Characterization of the MinD mutant MinDK16R revealed an additional role for MinE. While MinE does not induce MinDK16R oscillation, MinE does promote the accumulation of MinDK16R into static membrane-associated spiral-like structures. We propose that these structures may represent a stage in the dynamic Min protein oscillation cycle, therefore, suggesting that MinE has at least two roles in Min protein dynamics, regulating Min protein-membrane dissociation and regulating Min protein spiral formation. |
