Thermodynamic determinations for Cu2+ binding by amyloid-β peptides through mutation studies

CHED 1045

Tessa M. Carducci,, William D. Bush,, Lanying Q. Hatcher, Lian Hong, and John D. Simon, Department of Chemistry, Duke University, 124 Science Dr, Durham, NC 27708
Formation of senile plaques, the hallmark pathology of Alzheimer's disease, is shown in vitro to be triggered by Cu2+ chelation by the amyloid-β (Aβ) peptide. Through isothermal titration calorimetry, potential amino acid binding partners to Cu2+ were investigated. The following Aβ(1-16) mutants were also studied: acylated N-terminus, Y10F, H6A, H13A, H14A, H6AH13A, H6AH14A, and H13AH14A. A non-classical competitive binding model is used in which copper chelated to glycine [Cu(Gly)2] is titrated into buffered Aβ peptide solution. At pH 7.4 and 37C in HEPES buffer, we report reaction constants for Cu2+ binding by Aβ (1-16) and Aβ (1-16) mutant ligands, with conserved stoichiometry. Upon Cu2+ binding, a net transfer of protons from Aβ (1-16) and some Aβ (1-16) mutants to the buffer was found to occur. Future studies will aim to further quantify and determine the source(s) of buffer ionization using different buffers shown to be noncomplexing with Cu2+.