Protein nanopore-based, single-molecule exploration of copper binding to an antimicrobial-derived, histidine-containing chimera peptide

Langmuir. 2012 Dec 11;28(49):17079-91. doi: 10.1021/la303782d. Epub 2012 Nov 26.

Abstract

Metal ions binding exert a crucial influence upon the aggregation properties and stability of peptides, and the propensity of folding in various substates. Herein, we demonstrate the use of the α-HL protein as a powerful nanoscopic tool to probe Cu(2+)-triggered physicochemical changes of a 20 aminoacids long, antimicrobial-derived chimera peptide with a His residue as metal-binding site, and simultaneously dissect the kinetics of the free- and Cu(2+)-bound peptide interaction to the α-HL pore. Combining single-molecule electrophysiology on reconstituted lipid membranes and fluorescence spectroscopy, we show that the association rate constant between the α-HL pore and a Cu(2+)-free peptide is higher than that of a Cu(2+)-complexed peptide. We posit that mainly due to conformational changes induced by the bound Cu(2+) on the peptide, the resulting complex encounters a higher energy barrier toward its association with the protein pore, stemming most likely from an extra entropy cost needed to fit the Cu(2+)-complexed peptide within the α-HL lumen region. The lower dissociation rate constant of the Cu(2+)-complexed peptide from α-HL pore, as compared to that of Cu(2+)-free peptide, supports the existence of a deeper free energy well for the protein interaction with a Cu(2+)-complexed peptide, which may be indicative of specific Cu(2+)-mediated contributions to the binding of the Cu(2+)-complexed peptide within the pore lumen.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antimicrobial Cationic Peptides / chemistry
  • Bacterial Toxins / chemistry*
  • Binding Sites
  • Copper / chemistry*
  • Hemolysin Proteins / chemistry*
  • Histidine / chemistry*
  • Kinetics
  • Lipid Bilayers / chemistry*
  • Magainins / chemistry
  • Membrane Potentials
  • Nanopores
  • Peptides / chemical synthesis
  • Peptides / chemistry*
  • Protein Binding
  • Protein Conformation
  • Recombinant Fusion Proteins / chemical synthesis
  • Recombinant Fusion Proteins / chemistry*
  • Spectrometry, Fluorescence
  • Thermodynamics

Substances

  • Antimicrobial Cationic Peptides
  • Bacterial Toxins
  • Hemolysin Proteins
  • Lipid Bilayers
  • Magainins
  • Peptides
  • Recombinant Fusion Proteins
  • staphylococcal alpha-toxin
  • Histidine
  • Copper
  • cecropin A