To further investigate the HTT protein structure in its entirety and the influence of polyglutamine expansion within exon 1, we repeated the DSF and proteolysis studies using HTT-HAP40 samples containing either a pathological HD HTT with 54 glutamines (Q54) or an HTT with a partially deleted exon 1 (Δexon 1; comprising residues 80–3144, missing N17, polyglutamine and proline-rich domain). Here, HTT is linked to Huntington disease.