How Does the Spatial Confinement of FtsZ to a Membrane Surface Affect Its Polymerization Properties and Function?

Abstract

FtsZ is the cytoskeletal protein that organizes the formation of the septal ring and orchestrates bacterial cell division. Its association to the membrane is essential for its function. In this mini-review I will address the question of how this association can interfere with the structure and dynamic properties of the filaments and argue that its dynamics could also remodel the underlying lipid membrane through its activity. Thus, lipid rearrangement might need to be considered when trying to understand FtsZ’s function. This new element could help understand how FtsZ assembly coordinates positioning and recruitment of the proteins forming the septal ring inside the cell with the activity of the machinery involved in peptidoglycan synthesis located in the periplasmic space.

Crosslinking by ZapD drives the assembly of short FtsZ filaments into toroidal structures in solution

“…Our work demonstrates that ZapD can promote the assembly of FtsZ into higher-order toroidal structures in solution, formed by a meshwork of short, crosslinked filaments resembling those that form the division ring in bacterial cells 7,33,49,50,55,56 . These results are consistent with precurved FtsZ protofilaments, as suggested by the circular assemblies of FtsZ filaments flexibly attached to model membranes observed in several vitro reconstituted systems [57][58][59] . Besides, FtsZ can form ring-shaped structures with a 100-200 nm diameter on surfaces, as revealed by negative stain EM and AFM, which become even more prominent after FtsZ adsorption to lipid, carbon, or mica surfaces 12,13,60 or in the presence of molecular crowders such as methylcellulose or polyvinyl alcohol 17 .…”

“…The presence of ZapD can help, shape and provide stability to the network, spacing the filaments and crosslinking them into a discontinuous toroid. These features can be further modulated by surface effects at the cell membrane, acting as a scaffold for protein self-organization, a process analyzed experimentally 67,[89][90][91][92][93] . In addition, FtsZ can also polymerize into ~1µm diameter ring-like vortices when bound to artificial membranes, either through ZipA 94 , FtsA 95 , or using a membrane-targeting variant of FtsZ 96 .…”