InterPro domain: IPR010448

Torsins are membrane-associated ATPases. They belong to the AAA+ (ATPase associated with a variety of cellular activities) superfamily of ATPases, but they lack conserved catalytic residues typically found in related ATPases. Accordingly, Torsins do not display ATPase activity unless they are engaged by their regulatory cofactors lamina-associated polypeptide 1 (LAP1) or luminal domain-like LAP1 (LULL1) [ 1 ], which are type II transmembrane proteins located in the nuclear envelope and endoplasmic reticulum (ER) [ 2 ]. LAP1 and LULL1 integrate into the Torsin ring to produce the biologically active ATPase machine [ 3 ].

Torsion dystonia is an autosomal dominant movement disorder characterised by involuntary, repetitive muscle contractions and twisted postures. The most severe early-onset form of dystonia has been linked to mutations in the human DYT1 (TOR1A) gene encoding a protein termed torsinA. While causative genetic alterations have been identified, the function of torsin proteins and the molecular mechanism underlying dystonia remain unknown. It has been suggested that torsins play a role in effectively managing protein folding and that possible breakdown in a neuroprotective mechanism that is, in part, mediated by torsins may be responsible for the neuronal dysfunction associated with dystonia [ 4 ].

1. Regulation of Torsin ATPases by LAP1 and LULL1. Proc. Natl. Acad. Sci. U.S.A. 110, E1545-54
2. The AAA+ protein torsinA interacts with a conserved domain present in LAP1 and a novel ER protein. J. Cell Biol. 168, 855-62
3. The mechanism of Torsin ATPase activation. Proc. Natl. Acad. Sci. U.S.A. 111, E4822-31
4. Suppression of polyglutamine-induced protein aggregation in Caenorhabditis elegans by torsin proteins. Hum. Mol. Genet. 12, 307-19