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 [1,2]. 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 [3,4]. A single mutation in Torsin A causes early onset primary dystonia, a painful and severely disabling neuromuscular disease [3,4]. This entry represents the C-terminal AAA+ activator domain of LAP1.

1: Molecular cloning of one isotype of human lamina-associated polypeptide 1s and a topological analysis using its deletion mutants. Kondo Y, Kondoh J, Hayashi D, Ban T, Takagi M, Kamei Y, Tsuji L, Kim J, Yoneda Y; Biochem Biophys Res Commun 2002;294:770-778. PMID:12061773

2: cDNA cloning and characterization of lamina-associated polypeptide 1C (LAP1C), an integral protein of the inner nuclear membrane. Martin L, Crimaudo C, Gerace L; J Biol Chem 1995;270:8822-8828. PMID:7721789

3: How lamina-associated polypeptide 1 (LAP1) activates Torsin. Sosa BA, Demircioglu FE, Chen JZ, Ingram J, Ploegh HL, Schwartz TU; Elife. 2014;3:e03239. PMID:25149450

4: Structures of TorsinA and its disease-mutant complexed with an activator reveal the molecular basis for primary dystonia. Demircioglu FE, Sosa BA, Ingram J, Ploegh HL, Schwartz TU; Elife. 2016; [Epub ahead of print] PMID:27490483