Torsin-1A-interacting proteins 1 and 2 (TOIP 1/2), also known as LAP1 proteins (Lamina-associated polypeptide 1) are type 2 integral membrane proteins with a single membrane-spanning region of the inner nuclear membrane. These proteins interact with and activate Torsin A, an AAA+ ATPase localised to the endoplasmic reticulum (ER) through a perinuclear domain and forms a heterohexameric (LAP1-Torsin)3 ring that targets Torsin to the nuclear envelope. LAP1 has an atypical AAA+ fold and provides an arginine finger to the Torsin A active site to promote its ATPase activity. A single mutation in Torsin A causes early onset primary dystonia, a painful and severely disabling neuromuscular disease. This entry represents the C-terminal AAA+ activator domain of LAP1.
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