ZapD Crosslinking Drives FtsZ Filament Assembly

Core Concepts

ZapD crosslinks FtsZ filaments into ring-like structures, revealing the mechanism of FtsZ assembly.

Abstract

The study focuses on how ZapD proteins stabilize the FtsZ ring by crosslinking filaments. ZapD binds to the C-terminal domain of FtsZ, promoting bundling and reducing GTPase activity. Cryo-electron tomography reveals the 3D organization of ring-like structures formed by discontinuous filaments. The toroidal structures are similar in size to bacterial cells and are stabilized by lateral connections between filaments mediated by ZapD dimers. The concentration of ZapD influences the formation of straight bundles or toroids, with an equimolar ratio optimal for toroid assembly. Dimerization of ZapD is crucial for forming toroidal structures and straight bundles. These findings provide insights into the molecular mechanism behind FtsZ filament crosslinking and Z-ring stabilization.

Stats

ZapD binds to two moles of FtsZ per mole of protein.
Increasing concentrations of ZapD promote light scattering in samples containing FtsZ.
GTPase activity decreases to 30% with equimolar concentrations of ZapD.
Toroids have an outer diameter around 502 nm and a thickness of 127 nm.

Quotes

"Toroidal structures are composed of a meshwork of short filaments, crosslinked laterally by ZapD dimers."
"The preferential curvature of FtsZ filaments is preserved within a range of ZapD connections."

Key Insights Distilled From

Crosslinking by ZapD drives the assembly of short, discontinuous FtsZ filaments into ring-like structures in solution

by Meri... at www.biorxiv.org 01-12-2023

https://www.biorxiv.org/content/10.1101/2023.01.12.523557v1

Deeper Inquiries

How do these findings impact our understanding of bacterial cell division mechanisms

The findings presented in the study significantly impact our understanding of bacterial cell division mechanisms, particularly regarding the role of ZapD in stabilizing FtsZ filaments into ring-like structures. By demonstrating how ZapD crosslinks adjacent FtsZ filaments to form toroidal structures reminiscent of the Z-ring observed in vivo, this research sheds light on the molecular mechanism behind filament organization during cytokinesis. Understanding how proteins like ZapD contribute to maintaining the structural integrity of the Z-ring provides valuable insights into the overall process of bacterial cell division.

Could other proteins besides ZapD play a role in stabilizing the FtsZ ring

While ZapD has been identified as a key player in stabilizing FtsZ filaments and promoting their assembly into ring-like structures, it is possible that other proteins besides ZapD could also play a role in this process. Proteins interacting with FtsZ may have varying functions and mechanisms for modulating filament dynamics and organization within the divisome. Further exploration into additional FtsZ-associated proteins (Zaps) or other regulatory factors involved in stabilizing the FtsZ ring could provide a more comprehensive understanding of how these components work together to facilitate bacterial cell division.

How could the formation of straight bundles affect bacterial cell division differently than toroidal structures

The formation of straight bundles as opposed to toroidal structures could potentially affect bacterial cell division differently due to variations in filament alignment and stability. Straight bundles formed at high concentrations of crosslinking proteins like ZapD may exhibit different mechanical properties compared to toroids, impacting force generation and constriction during cytokinesis. The rigidity and orientation of straight bundles might influence how forces are distributed across the dividing cell, potentially altering the efficiency or dynamics of membrane constriction. Understanding these differences between straight bundles and toroidal structures can offer insights into how variations in protein interactions can impact bacterial cell division processes at a structural level.