Mutations on FtsZ lateral helix H3 that disrupt cell viability hamper reorganization of polymers on lipid surfaces

摘要

Abstract FtsZ filaments localize at the middle of the bacterial cell and participate in the formation of a contractile ring responsible for cell division. Previous studies demonstrated that the highly conserved negative charge of glutamate 83 and the positive charge of arginine 85 located in the lateral helix H3 bend of Escherichia coli FtsZ are required for in vivo cell division. In order to understand how these lateral mutations impair the formation of a contractile ring,we extend previous in vitro characterization of these mutants in solution to study their behavior on lipid modified surfaces. We study their interaction with ZipAand look at their reorganization on the surface. We found that the dynamic bundling capacity of the mutant proteins is deficient, and this impairment increases the more the composition and spatial arrangement of the reconstituted system resembles the situation inside the cell: mutant proteins completely fail to reorganize to form higher order aggregates when bound to an E.coli lipid surface through oriented ZipA.We conclude that these surface lateral point mutations affect the dynamic reorganization of FtsZ filaments into bundles on the cell membrane, suggesting that this event is relevant for generating force and completing bacterial division. Graphical abstract FtsZ is a bacterial cytoskeletal protein that forms a contractile ring at the midcell. In vivo studies had previously indicated that two mutants, E83Q and R85Q, with mutations in the lateral H3 helix, were unable to support bacterial division. In this paper we report in vitro studies of these mutants on lipid surfaces that show that they cannot form filament aggregates on E.coli lipids, indicating that lateral interactions between filaments are probably required for their condensation into functional constricting rings in vivo . Display Omitted Highlights ? Two mutations on helix H3 on FtsZ perturb its binding to ZipA on lipid membranes. ? Mutant's capacity to reorganize on the surface in the presence of GTP is hampered. ? Impaired surface reorganization detected could explain malfunction in vivo . ]]>