Fig. 1.

Proto-ring in cells and in reconstructed membrane systems. a. Diagram illustrating the position of essential divisome elements in Escherichia coli. Proto-ring elements are colored, while other divisome proteins are shown in dark gray. Light-gray circles represent the macromolecules contributing to the crowding of the cytoplasm. b. Reconstruction of proto-ring in membrane systems. Vesicles show the two alternative orientations of the reconstructed proto-ring relative to the vesicle lumen. c. Visualization of guanosine triphosphate (GTP)-induced FtsZ polymers reconstituted in different membrane systems. From left to right Transmission electron microscopy micrograph of ZipA-containing nanodiscs, scanning electron microscopy (SEM) micrograph of microbeads coated with native inner membrane, SEM micrograph showing FtsZ polymers growing in a three-dimensional network on a ZipA-containing lipid bilayer, confocal microscopy images of giant unilamellar vesicles with FtsZ assembled outside or inside the vesicles. Adapted from Hernández-Rocamora et al. (2012a), Jiménez et al. (2011), and Martos et al. (2012a), with permission