title: Uncovering principles that control septin-septin interactions.
abstract: Septins comprise a conserved family of GTPases important in cytokinesis. These proteins polymerize into filaments from rod-shaped heteromeric septin complexes. Septins interact with one another at two interfaces (NC and G) that alternate within the complex. Here, we show that small mutations at the N terminus greatly enhance the formation of SEPT2 homopolymers. Taking advantage of this mutation to examine polymer formation using SEPT2 alone, we show that both NC and G interfaces are required for filament formation. However, co-expression of wild type SEPT2 with SEPT2 containing mutations at either NC or G interfaces revealed that only the NC mutant suppressed filament formation. NC mutants are able to interact with one another at putative G interfaces, whereas G mutants fail to interact at NC interfaces. In addition, all promiscuous septin pairwise interactions occur at the G interface. These findings suggest that G interface interactions must occur before NC interactions during polymer formation.
authors: Program in Cell Biology, Department of Biochemistry, Hospital for Sick Children, University of Toronto, Toronto, Ontario M5G 1X8, Canada.
authors: Moshe S
authors: MS
authors: Kim
authors: Carol D
authors: CD
authors: Froese
authors: Hong
authors: H
authors: Xie
authors: William S
authors: WS
authors: Trimble
mesh_terms: D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D055503:Protein Multimerization / Q000502:physiology*; D017434:Protein Structure, Tertiary; D058112:Septins / Q000235:genetics / Q000378:metabolism*
chemical_list: D046912:Multiprotein Complexes; C000602252:SEPTIN2 protein, human; D058112:Septins