Wiktor Koźmiński's NMR group

Biological and Chemical Research Centre, University of Warsaw

  • Increase font size
  • Default font size
  • Decrease font size

New Article in Journal of the American Chemical Society

Print

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 Żerko, Wiktor Koźmiński, Judith Frydman, Lucio Frydman


htt

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.

 






Banner
Banner
Banner

Conferences organized

by us:


 

euromar 2017 logo

 


 

mmcebanner3

 


 

AUM4

 


We use cookies to improve our website and your experience when using it. Cookies used for the essential operation of the site have already been set.

I accept cookies from this site.