Hexa-Histidine, a Peptide with Versatile Applications in the Study of Amyloid-β(1–42) Molecular Mechanisms of Action

Amyloid β (Aβ) oligomers are the most neurotoxic forms of Aβ, and Aβ(1–42) is the prevalent Aβ peptide found in the amyloid plaques of Alzheimer’s disease patients. Aβ(25–35) is the shortest peptide that retains the toxicity of Aβ(1–42). Aβ oligomers bind to calmodulin (CaM) and calbindin-D28k with dissociation constants in the nanomolar Aβ(1–42) concentration range. Aβ and histidine-rich proteins have a high affinity for transition metal ions Cu(2+), Fe(3+) and Zn(2+). In this work, we show that the fluorescence of Aβ(1–42) HiLyte(TM)-Fluor555 can be used to monitor hexa-histidine peptide (His(6)) interaction with Aβ(1–42). The formation of His(6)/Aβ(1–42) complexes is also supported by docking results yielded by the MDockPeP Server. Also, we found that micromolar concentrations of His(6) block the increase in the fluorescence of Aβ(1–42) HiLyte(TM)-Fluor555 produced by its interaction with the proteins CaM and calbindin-D28k. In addition, we found that the His(6)-tag provides a high-affinity site for the binding of Aβ(1–42) and Aβ(25–35) peptides to the human recombinant cytochrome b(5) reductase, and sensitizes this enzyme to inhibition by these peptides. In conclusion, our results suggest that a His(6)-tag could provide a valuable new tool to experimentally direct the action of neurotoxic Aβ peptides toward selected cellular targets.