Cooperative ordering of treadmilling filaments in cytoskeletal networks of FtsZ and its crosslinker ZapA

Abstract

During bacterial cell division, the tubulin-homolog FtsZ forms a ring-like structure at the center of the cell. This Z-ring not only organizes the division machinery, but treadmilling of FtsZ filaments was also found to play a key role in distributing proteins at the division site. What regulates the architecture, dynamics and stability of the Z-ring is currently unknown, but FtsZ-associated proteins are known to play an important role. Here, using an in vitro reconstitution approach, we studied how the well-conserved protein ZapA affects FtsZ treadmilling and filament organization into large-scale patterns. Using high-resolution fluorescence microscopy and quantitative image analysis, we found that ZapA cooperatively increases the spatial order of the filament network, but binds only transiently to FtsZ filaments and has no effect on filament length and treadmilling velocity. Together, our data provides a model for how FtsZ-associated proteins can increase the precision and stability of the bacterial cell division machinery in a switch-like manner.

Essential dynamic interdependence of FtsZ and SepF for Z-ring and septum formation in Corynebacterium glutamicum

“…In this case, FtsZ has been shown to assemble into dynamic vortices in vitro without the need for accessory proteins, but critically relying on concentration thresholds 46 . Concentration dependence is also true for accessory proteins such as the bundling protein ZipA 48 , or ZapA 49 where the effect on FtsZ dynamics heavily relies on the protein concentrations used. In the bacterial cell FtsZ does not contain a membrane-binding domain and the self-assembly is counteracted by several parameters such as molecular crowding 50,51 , as well as spatial and temporary constraints for mid-cell localization.…”

Dynamics of bacterial cell division: Z ring condensation is essential for cytokinesis

“…To resolve this, we next investigated whether ZBPs affected FtsZ dynamics in vivo. ZBPs have been proposed to regulate FtsZ filament dynamics, stability, GTPase activity, and bundling, based both on in vitro biochemistry and in vivo genetic interactions (18)(19)(20)(21)(22)(23)(24)(25)(26)(27). We measured FtsZ's treadmilling velocity and subunit lifetime in strains as we changed the levels of individual ZBPs by deletion or overexpression ( Fig 3A, S2-4, Table S3).…”

“…Next, we investigated whether the ZBPs instead mediated filament bundling. ZBPs have been shown to mediate FtsZ filament bundling in vitro (19,21,(23)(24)(25)(26)(27), and lateral interactions between FtsZ filaments have been proposed to play a functional role in cytokinesis (28,29). We, therefore, investigated how each ZBP knockout, individually and in combination, affected Z ring morphology.…”

Spatial Variation of Microtubule Depolymerization in Large Asters Suggests Regulation by MAP Depletion

“…Our previous analysis of growing and shrinking ends used manual kymograph analysis of difference images and was restricted to the interior of the interphase asters (Ishihara et al 2014). Here, we applied a newly developed automated workflow (Caldas et al 2019;Caldas et al 2020), and systematically compared spatial differences in polymerization dynamics ( Fig. 2A).…”

“…To obtain spatial information regarding polymerization and depolymerization rates, we applied a recently developed workflow used to quantify treadmilling dynamics in bacterial cytoskeletal filaments (Caldas et al 2019;Caldas et al 2020). This method allows to track hundreds of growing and shrinking microtubule ends in an automated fashion, overcoming the limitations of a standard manual kymograph analysis.…”