Structure and dynamics of the Huntingtin Exon-1 N-Terminus

A solution NMR perspective

Maria Baias, Pieter E.S. Smith, Koning Shen, Lukasz A. Joachimiak, Szymon Zerko, Wiktor Koźmiński, Judith Frydman, Lucio Frydman

    Research output: Contribution to journalArticle

    Abstract

    Many neurodegenerative diseases are characterized by misfolding and aggregation of an expanded polyglutamine tract (polyQ). Huntington's Disease, caused by expansion of the polyQ. tract in exon 1 of the Huntingtin protein (Htt), is associated with aggregation and neuronal toxicity. Despite recent structural progress in understanding the structures of amyloid fibrils, little is known about the solution states of Htt in general, and about molecular details of their transition from soluble to aggregation-prone conformations in particular. This is an important question, given the increasing realization that toxicity may reside in soluble conformers. This study presents an approach that combines NMR with computational methods to elucidate the structural conformations of Htt Exon 1 in solution. Of particular focus was Htt's N17 domain sited N-terminal to the polyQ. tract, which is key to enhancing aggregation and modulate Htt toxicity. Such in-depth structural study of Htt presents a number of unique challenges: the long homopolymeric polyQ. tract contains nearly identical residues, exon 1 displays a high degree of conformational flexibility leading to a scaling of the NMR chemical shift dispersion, and a large portion of the backbone amide groups are solvent-exposed leading to fast hydrogen exchange and causing extensive line broadening. To deal with these problems, NMR assignment was achieved on a minimal Htt exon 1, comprising the N17 domain, a polyQ tract of 17 glutamines, and a short hexameric polyProline region that does not contribute to the spectrum. A pH titration method enhanced this polypeptide's solubility and, with the aid of ≤5D NMR, permitted the full assignment of N17 and the entire polyQ. tract. Structural predictions were then derived using the experimental chemical shifts of the Htt peptide at low and neutral pH, together with various different computational approaches. All these methods concurred in indicating that low-pH protonation stabilizes a soluble conformation where a helical region of N17 propagates into the polyQ region, while at neutral pH both N17 and the polyQ become largely unstructured-thereby suggesting a mechanism for how N17 regulates Htt aggregation.

    Original languageEnglish (US)
    Pages (from-to)1168-1176
    Number of pages9
    JournalJournal of the American Chemical Society
    Volume139
    Issue number3
    DOIs
    StatePublished - Jan 25 2017

    Fingerprint

    Exons
    Nuclear magnetic resonance
    Proteins
    Agglomeration
    Toxicity
    Conformations
    Chemical shift
    Neurodegenerative diseases
    polyglutamine
    Protonation
    Polypeptides
    Peptides
    Huntingtin Protein
    Computational methods
    Titration
    Huntington Disease
    Amides
    Glutamine
    Amyloid
    Neurodegenerative Diseases

    ASJC Scopus subject areas

    • Catalysis
    • Chemistry(all)
    • Biochemistry
    • Colloid and Surface Chemistry

    Cite this

    Baias, M., Smith, P. E. S., Shen, K., Joachimiak, L. A., Zerko, S., Koźmiński, W., ... Frydman, L. (2017). Structure and dynamics of the Huntingtin Exon-1 N-Terminus: A solution NMR perspective. Journal of the American Chemical Society, 139(3), 1168-1176. https://doi.org/10.1021/jacs.6b10893

    Structure and dynamics of the Huntingtin Exon-1 N-Terminus : A solution NMR perspective. / Baias, Maria; Smith, Pieter E.S.; Shen, Koning; Joachimiak, Lukasz A.; Zerko, Szymon; Koźmiński, Wiktor; Frydman, Judith; Frydman, Lucio.

    In: Journal of the American Chemical Society, Vol. 139, No. 3, 25.01.2017, p. 1168-1176.

    Research output: Contribution to journalArticle

    Baias, M, Smith, PES, Shen, K, Joachimiak, LA, Zerko, S, Koźmiński, W, Frydman, J & Frydman, L 2017, 'Structure and dynamics of the Huntingtin Exon-1 N-Terminus: A solution NMR perspective', Journal of the American Chemical Society, vol. 139, no. 3, pp. 1168-1176. https://doi.org/10.1021/jacs.6b10893
    Baias, Maria ; Smith, Pieter E.S. ; Shen, Koning ; Joachimiak, Lukasz A. ; Zerko, Szymon ; Koźmiński, Wiktor ; Frydman, Judith ; Frydman, Lucio. / Structure and dynamics of the Huntingtin Exon-1 N-Terminus : A solution NMR perspective. In: Journal of the American Chemical Society. 2017 ; Vol. 139, No. 3. pp. 1168-1176.
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