Roles of MinC and MinD in the site-specific septation block mediated by the MinCDE system of Escherichia coli

Abstract

The proper placement of the cell division site in Escherichia coli requires the site-specific inactivation of potential division sites at the ceil poles in a process that requires the coordinate action of the MinC, MinD, and MinE proteins. In the absence of MinE, the coordinate expression of MinC and MinD leads to a general inhibition of cell division. MinE gives topological specificity to the division inhibition process, so that the septation block is restricted to the cell poles. At normal levels of expression, both MinC and MinD are required for the division block. We show here that, when expressed at high levels, MinC acts as a division inhibitor even in the absence of MinD. The division inhibition that results from MinC overexpression in the absence of MinD is insensitive to the MinE topological specificity factor. The results suggest that MinC is the proximate cause of the septation block and that MinD plays two roles in the MinCDE system-it activates the MinC-dependent division inhibition mechanism and is also required for the sensitivity of the division inhibition system to the MinE topological specificity factor.In Escherichia coli, correct placement of the division septum involves selection of the proper site at midcell. This requires the site-specific inhibition of septation at potential septation sites that are present at the cell poles (9, 11). This process is controlled by the products of the minB operon, MinC, MinD, and MinE (12,13). We have previously shown that coexpression of minC and minD in the absence of MinE leads to the inhibition of septation at both polar and cellinternal potential division sites. Under normal conditions, the MinC/MinD division block is counteracted in a topologically specific fashion by MinE, so that septation is allowed at midcell but is still prevented at the cell poles. The absence of functional MinC or MinD protein or overexpression of minE leads to loss of this site-specific division inhibition process. This results in the frequent misplacement of division septa at cell poles, leading to the formation of small chromosomeless minicells (13).Further insight into the roles of the Min proteins came from the finding (14, 21) that MinC also plays an essential role in the division inhibition that results from expression of the dicB gene, a division inhibitor gene that is normally not expressed (1, 2). MinC/DicB division inhibition differs from MinC/MinD-mediated inhibition in that it is resistant to MinE (14). Because MinC is the common component of both the MinD-and DicB-dependent division inhibition systems, it was suggested that MinC is the component that is responsible for the division block in both systems, with MinD and DicB functioning as activators of the MinC-dependent division inhibitor (14).A candidate for the target of the division inhibitor is the ftsZ gene product. The ftsZ gene is an essential cell division gene which is part of a large cluster of genes at 2 min on the E. coli chromosome that are involved in murein metabolism and septum formation (11,16,22 ...

RNaseE and the other constituents of the RNA degradosome are components of the bacterial cytoskeleton

“…4F). The division block was not mediated by the endogenous division inhibitor MinC or the SOS division inhibitor SulA (27)(28)(29) as shown by the observation that filamentation was unaffected by the absence of either MinC or SulA (Fig. 4 E and G).…”

Evidence That Bacteriophage λ Kil Peptide Inhibits Bacterial Cell Division by Disrupting FtsZ Protofilaments and Sequestering Protein Subunits

“…SlmA by itself does not block FtsZ assembly. However, MinC and SlmA are each strongly activated by cofactors, which include the membrane protein MinD and specific SlmA-binding sites on DNA, respectively (24,54,55). These cofactors greatly enhance MinC and SlmA activity on FtsZ.…”

Two Mechanosensitive Channel Homologs Influence Division Ring Placement in Arabidopsis Chloroplasts

“…Minicell C (MinC) and MinD form a complex that negatively regulates FtsZ polymerization, while MinE acts as a topological specificity factor by inhibiting MinCD function (de Boer et al, 1989(de Boer et al, , 1991(de Boer et al, , 1992bHuang et al, 1996). All three proteins oscillate from pole to pole such that MinCD activity is restricted to the ends of the cell and FtsZ polymerization is allowed to progress only at mid-cell (Hu and Lutkenhaus, 1999;de Boer, 1999a, 1999b;Rowland et al, 2000;Fu et al, 2001;Hale et al, 2001).…”