title: Modulation of polyglutamine conformations and dimer formation by the N-terminus of huntingtin.
abstract: Polyglutamine expansions within different proteins are associated with nine different neurodegenerative diseases. There is growing interest in understanding the roles of flanking sequences from disease-relevant proteins in the intrinsic conformational and aggregation properties of polyglutamine. We report results from atomistic simulations and circular dichroism experiments that quantify the effect of the N-terminal 17-residue (Nt17) segment of the huntingtin protein on polyglutamine conformations and intermolecular interactions. We show that the Nt17 segment and polyglutamine domains become increasingly disordered as polyglutamine length (N) increases in Nt17-Q(N) constructs. Hydrophobic groups within Nt17 become sequestered in intramolecular interdomain interfaces. We also show that the Nt17 segment suppresses the intrinsic propensity of polyglutamine aggregation. This inhibition arises from the incipient micellar structures adopted by monomeric forms of the peptides with Nt17 segments. The degree of intermolecular association increases with increasing polyglutamine length and is governed mainly by associations between polyglutamine domains. Comparative analysis of intermolecular associations for different polyglutamine-containing constructs leads to clearer interpretations of recently published experimental data. Our results suggest a framework for fibril formation and identify roles for flanking sequences in the modulation of polyglutamine aggregation.
authors.affiliation: Department of Biomedical Engineering, Washington University in St Louis, One Brookings Drive, Campus Box 1097, St Louis, MO 63130, USA.
authors.forename: Tim E
authors.initials: TE
authors.lastname: Williamson
authors.forename: Andreas
authors.initials: A
authors.lastname: Vitalis
authors.forename: Scott L
authors.initials: SL
authors.lastname: Crick
authors.forename: Rohit V
authors.initials: RV
authors.lastname: Pappu
mesh_terms: D000595:Amino Acid Sequence; D002942:Circular Dichroism; D003198:Computer Simulation; D006801:Humans; D000071058:Huntingtin Protein; D057927:Hydrophobic and Hydrophilic Interactions; D066298:In Vitro Techniques; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000737:chemistry* / Q000235:genetics; D009687:Nuclear Proteins / Q000737:chemistry* / Q000235:genetics; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics; D010455:Peptides / Q000737:chemistry* / Q000235:genetics; D011487:Protein Conformation; D054730:Protein Interaction Domains and Motifs; D055503:Protein Multimerization; D017433:Protein Structure, Secondary; D013816:Thermodynamics
chemical_list: C086055:HTT protein, human; D000071058:Huntingtin Protein; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D010446:Peptide Fragments; D010455:Peptides; C097188:polyglutamine