A comparison of methionine, histidine and cysteine in copper(I)-binding peptides reveals differences relevant to copper uptake by organisms in diverse environments.

Published

Journal Article

The N-terminal, extracellular regions of eukaryotic high affinity copper transport (Ctr) proteins vary in composition of the Cu(i) binding amino acids: methionine, histidine, and cysteine. To examine why certain amino acids are exploited over others in Ctrs from different organisms, the relative Cu(i) binding affinity and the dependence of binding on pH were examined for 3 peptides of the sequence MG(2)XG(2)MK, where X is either Met, His, or Cys. Cu(i) affinity was examined using an ascorbic acid oxidation assay, an electrospray ionization mass spectrometry technique, and spectrophotometric titration with a competitive Cu(i) chelator. The relative affinities of the peptides with Cu(i) reveal a trend whereby Cys > His > Met at pH 7.4 and Cys > Met > His at pH 4.5. Ligand geometry and metric parameters were determined with X-ray absorption spectroscopy. Susceptibility of the peptides to oxidation by hydrogen peroxide and copper-catalyzed oxidative conditions was evaluated by mass spectrometry. These results support hypotheses as to why certain Cu(i) binding amino acids are preferred over others in proteins expressed at different pH and exposed to oxidative environments. The results also have implications for interpreting site-directed mutagenesis studies aimed at identifying copper binding amino acids in copper trafficking proteins.

Full Text

Duke Authors

Cited Authors

  • Rubino, JT; Chenkin, MP; Keller, M; Riggs-Gelasco, P; Franz, KJ

Published Date

  • January 2011

Published In

Volume / Issue

  • 3 / 1

Start / End Page

  • 61 - 73

PubMed ID

  • 21305075

Pubmed Central ID

  • 21305075

Electronic International Standard Serial Number (EISSN)

  • 1756-591X

International Standard Serial Number (ISSN)

  • 1756-5901

Digital Object Identifier (DOI)

  • 10.1039/c0mt00044b

Language

  • eng