Severs microtubules, probably in an ATP-dependent fashion. n ATP + n H2O + a microtubule = n ADP + n phosphate + (n+1) alpha/beta tubulin heterodimers. Homohexamer. The homohexamer is stabilized by ATP-binding. The homohexamer may adopt a ring conformation through which microtubules pass prior to being severed. Interacts with microtubules (By similarity). Localized to the perinuclear region of the cytoplasm in early embryos. Present in the cytoskeletal fraction. Belongs to the AAA ATPase family. Spastin subfamily. Lacks the conserved MIT domain, which is one of the features of the spastin family.