Investigation of Cu2+ Binding to Human and Rat Amyloid Fragments Aβ (1–16) with a Protein Nanopore

Abstract

Recent evidence shows that metal coordination by amyloid beta peptides (Aβ) determines structural alterations of peptides, and His-13 from Aβ is crucial for Cu(2+) binding. This study used the truncated, more soluble Aβ1-16 isoforms derived from human and rat amyloid peptides to explore their interaction with Cu(2+) by employing the membrane-immobilized α-hemolysin (α-HL) protein as a nanoscopic probe in conjunction with single-molecule electrophysiology techniques. Unexpectedly, the experimental data suggest that unlike the case of the human Aβ1-16 peptide, Cu(2+) complexation by its rat counterpart leads to an augmented association and dissociation kinetics of the peptide reversible interaction with the protein pore, as compared to the Cu(2+)-free peptide. Single-molecule electrophysiology data reveal that both human and rat Cu(2+)-complexed Aβ peptides induce a higher degree of current flow obstruction through the α-HL pore, as compared to the Cu(2+)-free peptides. It is suggested that morphology changes brought by Cu(2+) binding to such amyloidic fragments depend crucially upon the presence of the His-13 residue on the primary sequence of such peptide fragments, and the α-HL protein-based approach provides unique opportunities and challenges to probing metal-induced folding of peptides.