Filament-forming cytoskeletal GTPase. May play a role in cytokinesis (Potential). May play a role in the cytoarchitecture of neurons, including dendritic arborization and dendritic spines, and in GABAergic synaptic connectivity (By similarity). During Listeria monocytogenes infection, not required for the bacterial entry process, but restricts its efficacy. Septins polymerize into heterooligomeric protein complexes that form filaments, and can associate with cellular membranes, actin filaments and microtubules. Forms homooligomers. GTPase activity is required for filament formation. Interacts with SEPTIN7, SEPTIN9 and SEPTIN12. Partly colocalizes with stress fibers and microtubules. During bacterial infection, displays a collar shape structure next to actin at the pole of invading bacteria. Widely expressed, except in leukocytes. A chromosomal aberration involving SEPTIN11 may be a cause of chronic neutrophilic leukemia. Translocation t(4;11)(q21;q23) with KMT2A/MLL1. Belongs to the TRAFAC class TrmE-Era-EngA-EngB-Septin-like GTPase superfamily. Septin GTPase family. Contaminating sequence. Potential poly-A sequence.