PT  - JOURNAL ARTICLE
AU  - Diego A. Ramirez-Diaz
AU  - Adrian Merino-Salomon
AU  - Fabian Meyer
AU  - Michael Heymann
AU  - German Rivas
AU  - Marc Bramkamp
AU  - Petra Schwille
TI  - Bidirectional FtsZ filament treadmilling transforms lipid membranes via torsional stress
AID  - 10.1101/587790
DP  - 2020 Jan 01
TA  - bioRxiv
PG  - 587790
4099  - http://biorxiv.org/content/early/2020/06/12/587790.short
4100  - http://biorxiv.org/content/early/2020/06/12/587790.full
AB  - 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 designed an in vitro assay based on soft lipid tubes pulled from FtsZ decorated giant lipid vesicles (GUVs) by optical tweezers. FtsZ actively transformed these tubes into spring-like structures, where GTPase activity promoted spring compression. Operating the optical tweezers in lateral vibration mode and assigning spring constants to FtsZ coated tubes, we found that FtsZ rings indeed exerts 0.14 – 1.09 pN forces upon GTP hydrolysis, through torsional stress induced by bidirectional treadmilling. These directional forces could further be demonstrated to induce membrane budding with constricting necks on both, giant vesicles and E.coli cells devoid of their cell walls.Competing Interest StatementThe authors have declared no competing interest.