title: Roles for both FtsA and the FtsBLQ subcomplex in FtsN-stimulated cell constriction in Escherichia coli.
abstract: Escherichia coli FtsN is a bitopic membrane protein that is essential for triggering active cell constriction. A small periplasmic subdomain ((E) FtsN) is required and sufficient for function, but its mechanism of action is unclear. We isolated extragenic (E) FtsN*-suppressing mutations that restore division in cells producing otherwise non-functional variants of FtsN. These mapped to the IC domain of FtsA in the cytoplasm and to small subdomains of the FtsB and FtsL proteins in the periplasm. All FtsB and FtsL variants allowed survival without (E) FtsN, but many then imposed a new requirement for interaction between the cytoplasmic domain of FtsN ((N) FtsN) and FtsA. Alternatively, variants of FtsA, FtsB or FtsL acted synergistically to allow cell division in the complete absence of FtsN. Strikingly, moreover, substitution of a single residue in FtsB (E56) proved sufficient to rescue ΔftsN cells as well. In FtsN(+) cells, (E) FtsN*-suppressing mutations promoted cell fission at an abnormally small cell size, and caused cell shape and integrity defects under certain conditions. This and additional evidence support a model in which FtsN acts on either side of the membrane to induce a conformational switch in both FtsA and the FtsBLQ subcomplex to de-repress septal peptidoglycan synthesis and membrane invagination.
authors.affiliation: Department of Molecular Biology & Microbiology, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106-4960, USA.
authors.forename: Bing
authors.initials: B
authors.lastname: Liu
authors.forename: Logan
authors.initials: L
authors.lastname: Persons
authors.forename: Lynda
authors.initials: L
authors.lastname: Lee
authors.forename: Piet A J
authors.initials: PA
authors.lastname: de Boer
mesh_terms: D019943:Amino Acid Substitution; D018797:Cell Cycle Proteins / Q000378:metabolism; D002455:Cell Division; D002473:Cell Wall / Q000502:physiology; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development / Q000502:physiology* / Q000648:ultrastructure; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D050296:Microbial Viability; D008954:Models, Biological; D009154:Mutation; D010802:Phylogeny; D013489:Suppression, Genetic
chemical_list: D018797:Cell Cycle Proteins; D029968:Escherichia coli Proteins; C489310:FtsA protein, E coli; C456028:FtsB protein, E coli; C098711:FtsN protein, E coli; C068023:FtsQ protein, E coli; D008565:Membrane Proteins; C078387:ftsL protein, E coli