4ys9
From Proteopedia
Ataxin-3 Carboxy-Terminal Region - Crystal C1 (tetragonal)
Structural highlights
DiseaseATX3_HUMAN Defects in ATXN3 are the cause of spinocerebellar ataxia type 3 (SCA3) [MIM:109150; also known as Machado-Joseph disease (MJD). Spinocerebellar ataxia is a clinically and genetically heterogeneous group of cerebellar disorders. Patients show progressive incoordination of gait and often poor coordination of hands, speech and eye movements, due to degeneration of the cerebellum with variable involvement of the brainstem and spinal cord. SCA3 belongs to the autosomal dominant cerebellar ataxias type I (ADCA I) which are characterized by cerebellar ataxia in combination with additional clinical features like optic atrophy, ophthalmoplegia, bulbar and extrapyramidal signs, peripheral neuropathy and dementia. The molecular defect in SCA3 is the a CAG repeat expansion in ATXN3 coding region. Longer expansions result in earlier onset and more severe clinical manifestations of the disease.[1] FunctionATX3_HUMAN Deubiquitinating enzyme involved in protein homeostasis maintenance, transcription, cytoskeleton regulation, myogenesis and degradation of misfolded chaperone substrates. Binds long polyubiquitin chains and trims them, while it has weak or no activity against chains of 4 or less ubiquitins. Involved in degradation of misfolded chaperone substrates via its interaction with STUB1/CHIP: recruited to monoubiquitinated STUB1/CHIP, and restricts the length of ubiquitin chain attached to STUB1/CHIP substrates and preventing further chain extension. In response to misfolded substrate ubiquitination, mediates deubiquitination of monoubiquitinated STUB1/CHIP. Interacts with key regulators of transcription and represses transcription: acts as a histone-binding protein that regulates transcription.[2] [3] [4] MALE_ECO57 Involved in the high-affinity maltose membrane transport system MalEFGK. Initial receptor for the active transport of and chemotaxis toward maltooligosaccharides (By similarity). Publication Abstract from PubMedAn expansion of polyglutamine (polyQ) sequence in ataxin-3 protein causes spinocerebellar ataxia type 3, an inherited neurodegenerative disorder. The crystal structure of the polyQ-containing carboxy-terminal fragment of human ataxin-3 was solved at 2.2-A resolution. The Atxn3 carboxy-terminal fragment including 14 glutamine residues adopts both random coil and alpha-helical conformations in the crystal structure. The polyQ sequence in alpha-helical structure is stabilized by intrahelical hydrogen bonds mediated by glutamine side chains. The intrahelical hydrogen-bond interactions between glutamine side chains along the axis of the polyQ alpha-helix stabilize the secondary structure. Analysis of this structure furthers our understanding of the polyQ-structural characteristics that likely underlie the pathogenesis of polyQ-expansion disorders. The 2.2-Angstrom resolution crystal structure of the carboxy-terminal region of ataxin-3.,Zhemkov VA, Kulminskaya AA, Bezprozvanny IB, Kim M FEBS Open Bio. 2016 Feb 18;6(3):168-78. doi: 10.1002/2211-5463.12029. eCollection, 2016 Mar. PMID:27047745[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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