fig2: Toward cell division in vitro. Shown is a model of reconstitution of protein self-organization and gradient formation in artificial cell-shaped containers by minimal functional elements of the E. coli cell division machinery. Reaction/diffusion–induced oscillations of MinCDE proteins position FtsZ protofilaments to the center of the compartment, mimicking the first step in Z ring assembly. Adapted from Zieske and Schwille (2014).

Mentions: Most remarkably, this Min protein system can be demonstrated to represent the smallest possible set of biochemical agents for initiating self-organization and pattern formation (Loose et al., 2008), requiring two proteins, ATP as an energy source, and a membrane as a template to yield wave-like dynamic protein gradients on flat extended membranes. Introduced into cell-shaped compartments, the cellular oscillations could be reconstituted (Zieske and Schwille, 2013). Moreover, the bottom-up experiments clearly demonstrated how time-averaged gradients act as spatial cues to direct downstream processes (Zieske and Schwille, 2014). Specifically, proto-ring filaments of FtsZ, the primary constituent of the contractile Z ring, could be exclusively positioned in the middle of the synthetic compartment (Fig. 2). Although this is only the first, and by no means the crucial step toward reconstituting division of a membrane compartment based on protein self-assembly and self-organization, this shows the advantage of the approach of dissecting a phenomenon into simple functional modules, which can in principle be derived from any organism or even designed from scratch.