Polar localization of the MinD protein of Bacillus subtilis and its role in selection of the mid-cell division site

Abstract

Cell division in rod-shaped bacteria is initiated by formation of a ring of the tubulin-like protein FtsZ at mid-cell. Division site selection is controlled by a conserved division inhibitor MinCD, which prevents aberrant division at the cell poles. The Bacillus subtilis DivIVA protein controls the topological specificity of MinCD action. Here we show that DivIVA is targeted to division sites late in their assembly, after some MinCD-sensitive step requiring FtsZ and other division proteins has been passed. DivIVA then recruits MinD to the division sites preventing another division from taking place near the newly formed cell poles. Sequestration of MinD to the poles also releases the next mid-cell sites for division. Remarkably, this mechanism of DivIVA action is completely different from that of the equivalent protein MinE of Escherichia coli, even though both systems operate via the same division inhibitor MinCD.

FtsZ and the division of prokaryotic cells and organelles

“…And others, such as Bacillus subtilis, contain only MinCD. Consistent with the role of MinE in stimulating the oscillation of MinD, the MinC and MinD proteins of B. subtilis do not move but are tethered to the cell poles by another protein, DivIVA, which itself binds strongly to the cell poles 46 . Therefore, although it has a completely different structure and function, DivIVA is analogous to MinE in that it restricts the action of MinC to the cell poles and away from the future division site.…”

A Mechanism for Polar Protein Localization in Bacteria

“…9 However, MinCD can also (MinC more strongly than MinD) target past/present division locations independently of DivIVA. 7,8 Similarly, in a minD mutant, DivIVA simply localizes to division sites regardless of location, again demonstrating an affinity for some component of the cell division apparatus. 7 Thus in wild-type cells, MinCD/ DivIVA localize to the poles (old division sites), blocking cell division there.…”

“…7,8 Similarly, in a minD mutant, DivIVA simply localizes to division sites regardless of location, again demonstrating an affinity for some component of the cell division apparatus. 7 Thus in wild-type cells, MinCD/ DivIVA localize to the poles (old division sites), blocking cell division there. However, before septal constriction occurs and the cell divides, MinCD/DivIVA assemble approximately simultaneously at midcell, 7 and are retained there after division.…”

“…8 Polar localization is facilitated by the action of the protein DivIVA, which acts to anchor MinCD to the poles. 7,8 Targeting of MinCD to the poles, is dependent on DivIVA, as in filamentous cells lacking DivIVA, MinCD was partly distributed diffusively along the cell. 7,8 Furthermore, the localization and activity of MinD is believed to require ATP binding and possibly hydrolysis.…”

“…7,8 Targeting of MinCD to the poles, is dependent on DivIVA, as in filamentous cells lacking DivIVA, MinCD was partly distributed diffusively along the cell. 7,8 Furthermore, the localization and activity of MinD is believed to require ATP binding and possibly hydrolysis. 9 However, MinCD can also (MinC more strongly than MinD) target past/present division locations independently of DivIVA.…”