Fig. 1.

Schematic summary of membrane deformation by FtsZ. (a) FtsZ-YFP-mts subunits assembled into a curved protofilament, with the C-terminal membrane tether on the outside of the curve. (b) FtsZ-YFP-mts applied to the outside of thin, spherical liposomes, generated concave depressions on the membrane surface. (c) Formation of thin phospholipid tubes. When the concentration of FtsZ-YFP-mts was more than 4 μM, many thin lipid tubes appeared. These tubes were covered by FtsZ filaments which aligned parallel to the long axis of tubes. The curvature of these thin tubes in not easily related to that of the bending protofilaments. (d) Z rings formed on the inside of a tubular liposome by FtsZ-YFP-mts.. When FtsZ-YFP-mts was taken up by multilamellar tubular liposomes, it formed Z rings that generated a constriction force. (e) The membrane tether of mts-FtsZ-YFP is switched to the N-terminal D10, which is on the opposite side of the subunit. This membrane attachment is on the inside of the curved protofilament. (f) On thin spherical liposomes, it generates convex protrusions of the membrane surface. (g) The present study shows that when mts-FtsZ-YFP is applied to the outside of multilamellar tubular liposomes, it assembles inside-out Z rings that wrap around the outside and generate a constriction force by squeezing.