THE DISORDERED C-TERMINAL LINKER OF FTSZ REGULATES Z-RING ASSEMBLY AND CELL WALL METABOLISM DURING CELL DIVISION IN CAULOBACTER CRESCENTUS
Embargo until
2020-12-01
Date
2018-05-03
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Johns Hopkins University
Abstract
Cell division is an essential process in all life forms that requires regulated changes in cell shape. In bacteria, the physical changes in cell shape during cell division are tightly regulated by the multi-protein machinery known as the divisome. The divisome assembles at the incipient division site and covalently remodels the cell wall locally to cause constriction. Antibiotics such as penicillin target the cell wall to disrupt bacterial growth. Aside from quenching a basic science curiosity, understanding the essential functions of the divisome will thus provide molecular targets for antibiotic development and tools for manipulating bacterial growth. The cytoskeletal protein FtsZ that polymerizes into a dynamic ring-like scaffold called the ‘Z-ring’ for the recruitment of the divisome. The Z-ring directly or indirectly localizes all the members of the divisome, including cell wall remodeling enzymes and proteins that regulate their activities. The contributions and regulation of the structure and dynamics of the Z-ring to cell division are largely unknown. Investigating the role of the disordered C-terminal linker (CTL) region of FtsZ in the model bacterium Caulobacter crescentus, we discovered that the CTL affects Z-ring assembly. FtsZ lacking its CTL (∆CTL) forms misshapen Z-rings that appear wider and brighter compared to wildtype FtsZ by fluorescence microscopy. Surprisingly, despite recruiting the divisome and directing local cell wall synthesis, ∆CTL Z-rings cause cell wall defects that lead to envelope bulges and rapid lysis. Through in vitro characterization, we discovered that the CTL is important for maintaining fast turnover of monomers and limiting lateral interactions between FtsZ filaments. Furthermore, we developed a novel technique to image FtsZ assembly on its physiologically relevant platform - the cytoplasmic membrane. We observe that ∆CTL assembles as large, stable bundles on supported lipid bilayer membranes whereas wildtype FtsZ forms dynamic resolution-limited clusters. Taking our results together, we conclude that the CTL is essential for maintaining optimum organization and dynamics of FtsZ polymers for the assembly of a functional Z-ring that properly regulates cell wall metabolism.
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Keywords
FtsZ, Cell division, Bacteria