Septin complexes in Drosophila melanogaster

Septins are GTP-binding proteins that assemble into hetero-oligomeric complexes, which polymerize into filaments and rings at the cell cortex. These structures act as scaffolds and diffusion barriers and are prominent at the cleavage furrow and the cellularization front. The best-characterized Drosophila septin complex contains Septin1, Septin2 and Peanut (Pnut), was purified from embryos and forms filaments in vitro; Pnut is needed for cytokinesis in proliferating tissues. Septin4 and Septin5, paralogs of Septin1 and Septin2, form a second complex with Pnut.

Pnut is shared by both complexes and appears in each variant. The cytokinesis process is attached only to the Septin1-Septin2-Pnut complex, for which the genetic and biochemical evidence is strongest; the roles of the Septin4-Septin5 complex are less well characterized. Septin-associated proteins such as anillin (scra) are context, not parts. GTPase activity (GO:0003924) is given only to Septin1, Septin4 (SEPT2 class) and Pnut (SEPT7 class). Septin2 and Septin5 are SEPT6-class septins: recombinant Sep2 shows no GTPase activity (NOT annotation, PMID:25355953), and the Septin2 and Septin5 gene reviews treat their GTPase annotations as removed or over-annotated, so these two subunits carry actin filament binding (GO:0051015) instead, the core activity in their reviews (PMID:38728140). FlyBase groups realized by this module: SEPT-C (FBgg0002070). Subgroups folded into it: SEPT-C12P, SEPT-C45P. Participants were generated from the FlyBase gene-group membership and mapped to UniProtKB by projects/FLYBASE_GENE_GROUPS/generate_modules.py from module_specs/dmel_septin_complexes.yaml. Member genes with a gene review in this repository: pnut, Septin1, Septin2, Septin4, Septin5.