The solution structure of rat Aβ-(1–28) and its interaction with zinc ion: insights into the scarcity of amyloid deposition in aged rat brain

Abstract

The amyloid β-peptide (Aβ) is a major component of insoluble amyloid deposits in Alzheimer’s disease, and the ability of the β-peptide to exist in different conformations is dependent on residues 1–28 [β-(1–28)]. However, different from humans, no Aβ amyloid deposition has been found in aged rats’ brains. Studying the three-dimensional solution structure of rat Aβ-(1–28) and the binding circumstance of Zn²⁺ is beneficial to a clear understanding of the potential role of Zn²⁺ in Alzheimer-associated neuropathogenesis and to suggest why there is no amyloid deposition in aged rats’ brains. Here we used nuclear magnetic resonance (NMR) spectroscopy to determine the solution structure of rat Aβ-(1–28) and the binding constant of Zn²⁺ to rat Aβ-(1–28). Our results suggest that (1) the three-dimensional solution structure of rat Aβ-(1–28) is more stable than that of human Aβ-(1–28) in DMSO-d ₆ and that a helical region from Glu16 to Val24 exists in the rat Aβ-(1–28); (2) the affinity of Zn²⁺ for rat Aβ-(1–28) is lower than that for human Aβ-(1–28) and the NMR data suggest that Arg13, His6, and His14 residues provide the primary binding sites for Zn²⁺; and (3) the proper binding of Zn²⁺ to rat Aβ-(1–28) can induce the peptide to change to a more stable conformation.