Septins polymerize into heterooligomeric protein complexes that form filaments, and can associate with cellular membranes, actin filaments and microtubules. GTPase activity is required for filament formation (By similarity). Interacts with SEPT2 and SEPT5. Interaction with SEPT4 not detected. In platelets, associated with a complex containing STX4 (By similarity). Interacts with PARK2. This interaction leads to SEPT5 ubiquitination and degradation.