Huntingtin N-Terminal Monomeric and Multimeric Structures Destabilized by Covalent Modification of Heteroatomic Residues

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...