Gene-Directed FtsZ Ring Assembly Generates Constricted Liposomes with Stable Membrane Necks.

Abstract

Mimicking bacterial cell division in well-defined cell-free systems has the potential to elucidate the minimal set of proteins required for cytoskeletal formation, membrane constriction, and final abscission. Membrane-anchored FtsZ polymers are often regarded as a sufficient system to realize this chain of events. By using purified FtsZ and its membrane-binding protein FtsA or the gain-of-function mutant FtsA* expressed in PURE (Protein synthesis Using Reconstituted Elements) from a DNA template, it is shown in this study that cytoskeletal structures are formed, and yield constricted liposomes exhibiting various morphologies. However, the resulting buds remain attached to the parental liposome by a narrow membrane neck. No division events can be monitored even after long-time tracking by fluorescence microscopy, nor when the osmolarity of the external solution is increased. The results provide evidence that reconstituted FtsA-FtsZ proto-rings coating the membrane necks are too stable to enable abscission. The prospect of combining a DNA-encoded FtsZ system with assisting mechanisms to achieve synthetic cell division is discussed.