His₆-Ataxin-3 (MJD protein 1),

Defects in the ATXN3 gene are the cause of Machado-Joseph disease (MJD), also known as spinorerebellar ataxia 3. MJD is an autosomal dominant neurodegenerative disorder caused by an expansion of a (CAG)n repeat in the ATXN3 gene resulting in polymorphic protein forms in the C-terminal poly-glutamine region. Ataxin-3 protein belongs to a novel group of cysteine proteases similar to USP-type ubiquitin proteases and has deubiquitinating activity in vitro. The full-length protein contains an N-terminal Josephin domain, two ubiquitin interacting motifs (UIMs), and a variable C-terminus consisting of a polyglutamine stretch and tail. Ataxin-3 activity may have a role in MJD pathogenesis by influencing ubiquitin-dependent pathways that control protein folding and stability. This recombinant protein is N-terminally tagged. (Accession # NP_004984).