Bactofilin-mediated organization of the ParABS chromosome segregation system in Myxococcus xanthus

Abstract

In bacteria, homologs of actin, tubulin, and intermediate filament proteins often act in concert with bacteria-specific scaffolding proteins to ensure the proper arrangement of cellular components. Among the bacteria-specific factors are the bactofilins, a widespread family of polymer-forming proteins whose biology is poorly investigated. Here, we study the three bactofilins BacNOP in the rod-shaped bacterium Myxococcus xanthus. We show that BacNOP co-assemble into elongated scaffolds that restrain the ParABS chromosome segregation machinery to the subpolar regions of the cell. The centromere (parS)-binding protein ParB associates with the pole-distal ends of these structures, whereas the DNA partitioning ATPase ParA binds along their entire length, using the newly identified protein PadC (MXAN_4634) as an adapter. The integrity of these complexes is critical for proper nucleoid morphology and chromosome segregation. BacNOP thus mediate a previously unknown mechanism of subcellular organization that recruits proteins to defined sites within the cytoplasm, far off the cell poles.

Competition between DivIVA and the nucleoid for ParA binding promotes segrosome separation and modulates mycobacterial cell elongation

“…In S. coelicolor, ParA, due to its interaction with a polar complex, anchors the oriC of the apical chromosome at the hyphal tip and maintains its constant distance to the tip (Kois-Ostrowska et al, 2016). Considering the distance between the nucleoid and DivIVA complex at the pole, it is likely that other, additional protein(s) takes part in the ParB-oriC positioning at a specific distance from the old pole in M. smegmatis, similarly as in M. xantus (Lin et al, 2017).…”

“…Similarly, in hyphal S. coelicolor, the interaction between ParA and a component of the polarisome complex, the Scy protein, is required for apical attachment of oriC (Ditkowski et al, 2013;Kois-Ostrowska et al, 2016). Interestingly, in M. xanthus ParA interaction with bactofilin scaffolds constrains the chromosome segregation machinery to the subpolar regions of the cell (Lin et al, 2017). ParA and ParB proteins may also interact with a DNA replication protein DnaA in B. subtilis (Murray and Errington, 2008) and with a cell division protein MipZ in C. crescentus (Kiekebusch et al, 2012), which suggests that they coordinate chromosome segregation with chromosome replication and cell division, respectively.…”

The Helicobacter pylori cell shape promoting protein Csd5 interacts with the cell wall, MurF, and the bacterial cytoskeleton

“…Two non-enzymatic proteins, CcmA and Csd5, were also identified in these screens. H. pylori CcmA has homology to bactofilins, bacterial cytoskeletal elements capable of self-assembly without a cofactor that are widely distributed in bacteria (Kühn et al, 2010) and often present as multiple (1-5) non-redundant paralogs indicating divergent cellular roles (Bulyha et al, 2013;Lin et al, 2017). In Caulobacter crescentus, the bactofilins BacA and BacB form membrane associated cytoplasmic filaments that associate with the inner membrane to direct stalk PG synthesis (Kühn et al, 2010).…”

BacStalk: a comprehensive and interactive image analysis software tool for bacterial cell biology

“…xanthus (37). Here, the 2D representation provides important information about the spatial arrangement of the filaments in the cell that cannot be appreciated in the standard 1D demo-graphs ( Fig.…”