Condensation of FtsZ filaments can drive bacterial cell division

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 106; no. 1; pp. 121 - 126
• Main Authors: Lan, Ganhui, Daniels, Brian R, Dobrowsky, Terrence M, Wirtz, Denis, Sun, Sean X
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 06.01.2009; National Acad Sciences
• Subjects: Bacteria; Bacterial Proteins - metabolism; Bacterial Proteins - physiology; Bacterial Proteins - ultrastructure; Biological Sciences; Biomechanical Phenomena; Cell Division; Cell growth; Cell walls; Computer applications; Computer Simulation; Condensation; Contractility; Cytoskeletal Proteins - metabolism; Cytoskeletal Proteins - physiology; Cytoskeletal Proteins - ultrastructure; Escherichia coli - cytology; Filaments; Fluorescence; Free energy; GTP; Guanosine Triphosphate - metabolism; Hydrolysis; Modeling; Models, Molecular; Monomers; Motility; Organelles; Polymers
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0807963106

Forces are important in biological systems for accomplishing key cell functions, such as motility, organelle transport, and cell division. Currently, known force generation mechanisms typically involve motor proteins. In bacterial cells, no known motor proteins are involved in cell division. Instead, a division ring (Z-ring) consists of mostly FtsZ, FtsA, and ZipA is used to exerting a contractile force. The mechanism of force generation in bacterial cell division is unknown. Using computational modeling, we show that Z-ring formation results from the colocalization of FtsZ and FtsA mediated by the favorable alignment of FtsZ polymers. The model predicts that the Z-ring undergoes a condensation transition from a low-density state to a high-density state and generates a sufficient contractile force to achieve division. FtsZ GTP hydrolysis facilitates monomer turnover during the condensation transition, but does not directly generate forces. In vivo fluorescence measurements show that FtsZ density increases during division, in accord with model results. The mechanism is akin to van der Waals picture of gas-liquid condensation, and shows that organisms can exploit microphase transitions to generate mechanical forces.