title: Huntingtin N-Terminal Monomeric and Multimeric Structures Destabilized by Covalent Modification of Heteroatomic Residues.
abstract: Early stage oligomer formation of the huntingtin protein may be driven by self-association of the 17-residue amphipathic α-helix at the protein's N-terminus (Nt17). Oligomeric structures have been implicated in neuronal toxicity and may represent important neurotoxic species in Huntington's disease. Therefore, a residue-specific structural characterization of Nt17 is crucial to understanding and potentially inhibiting oligomer formation. Native electrospray ion mobility spectrometry-mass spectrometry (IMS-MS) techniques and molecular dynamics simulations (MDS) have been applied to study coexisting monomer and multimer conformations of Nt17, independent of the remainder of huntingtin exon 1. MDS suggests gas-phase monomer ion structures comprise a helix-turn-coil configuration and a helix-extended-coil region. Elongated dimer species comprise partially helical monomers arranged in an antiparallel geometry. This stacked helical bundle may represent the earliest stages of Nt17-driven oligomer formation. Nt17 monomers and multimers have been further probed using diethylpyrocarbonate (DEPC). An N-terminal site (N-terminus of Threonine-3) and Lysine-6 are modified at higher DEPC concentrations, which led to the formation of an intermediate monomer structure. These modifications resulted in decreased extended monomer ion conformers, as well as a reduction in multimer formation. From the MDS experiments for the dimer ions, Lys6 residues in both monomer constituents interact with Ser16 and Glu12 residues on adjacent peptides; therefore, the decrease in multimer formation could result from disruption of these or similar interactions. This work provides a structurally selective model from which to study Nt17 self-association and provides critical insight toward Nt17 multimerization and, possibly, the early stages of huntingtin exon 1 aggregation.
authors.affiliation: †C. Eugene Bennett Department of Chemistry, ‡WVNano Safe Initiative, and §The Center for Neuroscience, West Virginia University, Morgantown, West Virginia 26506, United States.
authors.forename: James R
authors.initials: JR
authors.lastname: Arndt
authors.affiliation: †C. Eugene Bennett Department of Chemistry, ‡WVNano Safe Initiative, and §The Center for Neuroscience, West Virginia University, Morgantown, West Virginia 26506, United States.
authors.forename: Samaneh Ghassabi
authors.initials: SG
authors.lastname: Kondalaji
authors.affiliation: †C. Eugene Bennett Department of Chemistry, ‡WVNano Safe Initiative, and §The Center for Neuroscience, West Virginia University, Morgantown, West Virginia 26506, United States.
authors.forename: Megan M
authors.initials: MM
authors.lastname: Maurer
authors.affiliation: †C. Eugene Bennett Department of Chemistry, ‡WVNano Safe Initiative, and §The Center for Neuroscience, West Virginia University, Morgantown, West Virginia 26506, United States.
authors.forename: Arlo
authors.initials: A
authors.lastname: Parker
authors.affiliation: †C. Eugene Bennett Department of Chemistry, ‡WVNano Safe Initiative, and §The Center for Neuroscience, West Virginia University, Morgantown, West Virginia 26506, United States.
authors.forename: Justin
authors.initials: J
authors.lastname: Legleiter
authors.affiliation: †C. Eugene Bennett Department of Chemistry, ‡WVNano Safe Initiative, and §The Center for Neuroscience, West Virginia University, Morgantown, West Virginia 26506, United States.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Valentine
mesh_terms: D004047:Diethyl Pyrocarbonate / Q000737:chemistry; D006801:Humans; D000071058:Huntingtin Protein; D008239:Lysine / Q000737:chemistry; D013058:Mass Spectrometry; D056004:Molecular Dynamics Simulation; D009419:Nerve Tissue Proteins / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry; D011487:Protein Conformation; D055503:Protein Multimerization; D055550:Protein Stability; D017433:Protein Structure, Secondary; D013912:Threonine / Q000737:chemistry
chemical_list: C086055:HTT protein, human; D000071058:Huntingtin Protein; D009419:Nerve Tissue Proteins; D010455:Peptides; D013912:Threonine; D008239:Lysine; D004047:Diethyl Pyrocarbonate