title: Proteolysis-Dependent Remodeling of the Tubulin Homolog FtsZ at the Division Septum in Escherichia coli.
abstract: During bacterial cell division a dynamic protein structure called the Z-ring assembles at the septum. The major protein in the Z-ring in Escherichia coli is FtsZ, a tubulin homolog that polymerizes with GTP. FtsZ is degraded by the two-component ATP-dependent protease ClpXP. Two regions of FtsZ, located outside of the polymerization domain in the unstructured linker and at the C-terminus, are important for specific recognition and degradation by ClpXP. We engineered a synthetic substrate containing green fluorescent protein (Gfp) fused to an extended FtsZ C-terminal tail (residues 317-383), including the unstructured linker and the C-terminal conserved region, but not the polymerization domain, and showed that it is sufficient to target a non-native substrate for degradation in vitro. To determine if FtsZ degradation regulates Z-ring assembly during division, we expressed a full length Gfp-FtsZ fusion protein in wild type and clp deficient strains and monitored fluorescent Z-rings. In cells deleted for clpX or clpP, or cells expressing protease-defective mutant protein ClpP(S97A), Z-rings appear normal; however, after photobleaching a region of the Z-ring, fluorescence recovers ~70% more slowly in cells without functional ClpXP than in wild type cells. Gfp-FtsZ(R379E), which is defective for degradation by ClpXP, also assembles into Z-rings that recover fluorescence ~2-fold more slowly than Z-rings containing Gfp-FtsZ. In vitro, ClpXP cooperatively degrades and disassembles FtsZ polymers. These results demonstrate that ClpXP is a regulator of Z-ring dynamics and that the regulation is proteolysis-dependent. Our results further show that FtsZ-interacting proteins in E. coli fine-tune Z-ring dynamics.
authors.affiliation: Department of Cell and Molecular Biology, The University of Rhode Island, Kingston, Rhode Island, United States of America.
authors.forename: Marissa G
authors.initials: MG
authors.lastname: Viola
authors.affiliation: Department of Cell and Molecular Biology, The University of Rhode Island, Kingston, Rhode Island, United States of America.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: LaBreck
authors.affiliation: Department of Cell and Molecular Biology, The University of Rhode Island, Kingston, Rhode Island, United States of America.
authors.forename: Joseph
authors.initials: J
authors.lastname: Conti
authors.affiliation: Department of Cell and Molecular Biology, The University of Rhode Island, Kingston, Rhode Island, United States of America.
authors.forename: Jodi L
authors.initials: JL
authors.lastname: Camberg
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D001704:Biopolymers / Q000378:metabolism; D002455:Cell Division; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism*; D005456:Fluorescent Dyes / Q000378:metabolism; D059748:Proteolysis
chemical_list: D001426:Bacterial Proteins; D001704:Biopolymers; D003598:Cytoskeletal Proteins; D005456:Fluorescent Dyes; C071525:FtsZ protein, Bacteria