FtsZ induces membrane deformations via torsional stress upon GTP hydrolysis

Abstract

FtsZ is a key component in bacterial cell division, being the primary protein of the presumably contractile Z ring. In vivo and in vitro, it shows two distinctive features that could so far, however, not be mechanistically linked: self-organization into directionally treadmilling vortices on solid supported membranes, and shape deformation of flexible liposomes. In cells, circumferential treadmilling of FtsZ was shown to recruit septum-building enzymes, but an active force production remains elusive. To gain mechanistic understanding of FtsZ dependent membrane deformations and constriction, we design an in vitro assay based on soft lipid tubes pulled from FtsZ decorated giant lipid vesicles (GUVs) by optical tweezers. FtsZ filaments actively transform these tubes into spring-like structures, where GTPase activity promotes spring compression. Operating the optical tweezers in lateral vibration mode and assigning spring constants to FtsZ coated tubes, the directional forces that FtsZ-YFP-mts rings exert upon GTP hydrolysis can be estimated to be in the pN range. They are sufficient to induce membrane budding with constricting necks on both, giant vesicles and E.coli cells devoid of their cell walls. We hypothesize that these forces result from torsional stress in a GTPase activity dependent manner.

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

“…Since its first description ( Dai and Lutkenhaus, 1991 ; Pla et al, 1991 ; de Boer et al, 1992 ; RayChaudhuri and Park, 1992 ), much work has focused in understanding how it behaves in vitro and how it interacts with other proteins. We know that membrane association is essential for its function and that, even when attached through an inserted transmembrane region, in the absence of any of the proteins present in vivo , it displays a dynamic rich behavior and deforms membranes ( Osawa et al, 2009 ; Caldas et al, 2019 ; Ramirez-Diaz et al, 2021 ).…”

The Longitudinal Dividing Bacterium Candidatus Thiosymbion Oneisti Has a Natural Temperature-Sensitive FtsZ Protein with Low GTPase Activity

“…These mutants can form functional Z-rings at midcell at the permissive temperature of 30 °C, but fail to localize at the nonpermissive temperature of 42 °C. Assembly characteristics of FtsZ in vitro do not always correspond with features in vivo as has been reported [ 45 , 46 ]. For example, some temperature-sensitive FtsZ mutants have measurable low GTPase activities in vitro.…”

“…Seven temperature-sensitive alleles of FtsZ EC have been described until now: FtsZ84 (G105S), FtsZ26, FtsZ6460 (G109S), FtsZ972 (A129T), FtsZ2066 (V157M), FtsZ9124 (P203L), and FtsZ2863 (A239V) [44]. These mutants can form functional Z-rings at midcell at the permissive temperature of 30 • C, but fail to localize at the nonpermissive temperature of 42 • C. Assembly characteristics of FtsZ in vitro do not always correspond with features in vivo as has been reported [45,46]. For example, some temperature-sensitive FtsZ mutants have measurable low GTPase activities in vitro.…”

Membrane rigidity regulates E. coli proliferation rates

“…Despite the great advances in super-resolution microscopy 72 , the biochemical routes of active cytokinetic force production and reactive membrane rigidity remain however elusive. Nevertheless, FtsZ and membrane lipids continue to be the primary protein and the mechanical object most often targeted in the very prolific research field that keeps still at resolving this intriguing biological problem 73 – 75 . Alongside such vibrating research avenue, we have here contributed robust experimental evidence on the relevant membrane automatisms that regulate prokaryote cell proliferation in E. coli .…”