Species- and C-terminal linker-dependent variations in the dynamic behavior of FtsZ on membranes in vitro

Bacterial cell division requires the assembly of FtsZ protofilaments into a dynamic structure called the 'Z-ring'. The Z-ring recruits the division machinery and directs local cell wall remodeling for constriction. The organization and dynamics of protofilaments within the Z-ring coordinate local cell wall synthesis during cell constriction, but their regulation is largely unknown. The disordered C-terminal linker (CTL) region of Caulobacter crescentus FtsZ (CcFtsZ) regulates polymer structure and turnover in solution in vitro, and regulates Z-ring structure and activity of cell wall enzymes in vivo. To investigate the contributions of the CTL to the polymerization properties of FtsZ on its physiological platform, the cell membrane, we reconstituted CcFtsZ polymerization on supported lipid bilayers (SLB) and visualized polymer dynamics and structure using total internal reflection fluorescence microscopy. Unlike Escherichia coli FtsZ protofilaments that organized into large, bundled patterns, CcFtsZ protofilaments assembled into small, dynamic clusters on SLBs. Moreover, CcFtsZ lacking its CTL formed large networks of straight filament bundles that underwent slower turnover than the dynamic clusters of wildtype FtsZ. Our in vitro characterization provides novel insights into species- and CTL-dependent differences between FtsZ assembly properties that are relevant to Z-ring assembly and function on membranes in vivo.