A Mets motif peptide found in copper transport proteins selectively binds Cu(I) with methionine-only coordination.
Mets motifs, which refer to methionine-rich sequences found in the high-affinity copper transporter Ctr1, also appear in other proteins involved in copper trafficking and homeostasis, including other Ctrs as well as Pco and Cop proteins isolated from copper-resistant bacteria. To understand the coordination chemistry utilized by these proteins, we studied the copper binding properties of a peptide labeled Mets7-PcoC with the sequence Met-Thr-Gly-Met-Lys-Gly-Met-Ser. By comparing this sequence to a series of mutants containing noncoordinating norleucine in place of methionine, we confirm that all three methionine residues are involved in a thioether-only binding site that is selective for Cu(I). Two independent methods, one based on mass spectrometry and one based on rate differences for the copper-catalyzed oxidation of ascorbic acid, provide an effective K(D) of approximately 2.5 microM at pH 4.5 for the 1:1 complex of Mets7-PcoC with Cu(I). These results establish that a relatively simple peptide containing an MX(2)MX(2)M motif is sufficient to bind Cu(I) with an affinity that corresponds well with its proposed biological function of extracellular copper acquisition.
Jiang
Jianfeng
J
Department of Chemistry, Duke University, P.O. Box 90346, Durham, North Carolina 27708, USA.
Nadas
Istvan A
IA
Kim
M Alison
MA
Franz
Katherine J
KJ
D000595:Amino Acid Sequence; D001205:Ascorbic Acid / Q000494:pharmacology; D001692:Biological Transport; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism*; D003300:Copper / Q000378:metabolism*; D008715:Methionine / Q000737:chemistry* / Q000378:metabolism*; D009842:Oligopeptides / Q000737:chemistry* / Q000378:metabolism*; D010084:Oxidation-Reduction; D010455:Peptides / Q000737:chemistry* / Q000378:metabolism*; D021241:Spectrometry, Mass, Electrospray Ionization
D002352:Carrier Proteins; C000610395:Mets7 peptide; D009842:Oligopeptides; D010455:Peptides; D003300:Copper; D008715:Methionine; D001205:Ascorbic Acid