title: Septin filament formation is essential in budding yeast.
abstract: Septins are GTP-binding proteins that form ordered, rod-like multimeric complexes and polymerize into filaments, but how such supramolecular structure is related to septin function was unclear. In Saccharomyces cerevisiae, four septins form an apolar hetero-octamer (Cdc11-Cdc12-Cdc3-Cdc10-Cdc10-Cdc3-Cdc12-Cdc11) that associates end-to-end to form filaments. We show that septin filament assembly displays previously unanticipated plasticity. Cells lacking Cdc10 or Cdc11 are able to divide because the now-exposed subunits (Cdc3 or Cdc12, respectively) retain an ability to homodimerize via their so-called G interface, thereby allowing for filament assembly. In such cdc10Δ and cdc11Δ cells, the remaining septins, like wild-type complexes, localize to the cortex at the bud neck and compartmentalize nonseptin factors, consistent with a diffusion barrier composed of continuous filaments in intimate contact with the plasma membrane. Conversely, Cdc10 or Cdc11 mutants that cannot self-associate, but "cap" Cdc3 or Cdc12, respectively, prevent filament formation, block cortical localization, and kill cells.
authors.affiliation: Division of Biochemistry and Molecular Biology, Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA.
authors.forename: Michael A
authors.initials: MA
authors.lastname: McMurray
authors.forename: Aurelie
authors.initials: A
authors.lastname: Bertin
authors.forename: Galo
authors.initials: G
authors.lastname: Garcia
authors.forename: Lisa
authors.initials: L
authors.lastname: Lam
authors.forename: Eva
authors.initials: E
authors.lastname: Nogales
authors.forename: Jeremy
authors.initials: J
authors.lastname: Thorner
mesh_terms: D020043:Genes, Essential; D011994:Recombinant Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D058112:Septins / Q000378:metabolism*
chemical_list: D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; D058112:Septins