Fig. 2. Inwards FtsZ-induced conical deformations are geometrically equivalent to spring-like deformations on a tubular surface.

a To characterize the protein structures forming the cone-like deformations, we stretched the deformed vesicle membrane into a tubular geometry. Large and soft lipid tubes were pulled from weakly surface-attached GUVs by moving the GUVs relative to an optically trapped bead. b A representative time acquisition shows that FtsZ-YFP-mts entered the tube promoting coiling as a function of time (N = 12). Clustering of protein toward the tip correlates with a spring-like shape. Green and magenta corresponds to fluorescence signal of FtsZ-YFP-mts and lipid, respectively. c To rule out that artificial attachment of the FtsZ-YFP-mts is responsible of the helical transformation, we reconstituted wild-type FtsZ anchored to the membrane via ZipA. When wild-type FtsZ was added to ZipA-decorated vesicles, rings were self-assembled causing inwards cone-like deformations (N = 74) such as in the case of FtsZ-YFP-mts. d After pulling lipid tubes, similar helical deformations and supercoiled regions were observed confirming that torsion is related to the FtsZ core of the polymer (N = 3 out of 18 pulled tubes). Fluorescence signal of wt-FtsZ-Alexa 488 is shown in green while siZipA remains unlabeled and lipids are shown in magenta. (Scale bar = 2 µm).