title: Mass spectrometric determination of the coordination geometry of potential copper(II) surrogates for the mammalian prion protein octarepeat region.
abstract: The N-terminal domain of mammalian prion proteins contains several tandem repeats of the octapeptide PHGGGWGQ, each one capable of selectively binding up to 1 equiv of Cu2+. Under saturating conditions Cu2+ is known to coordinate the HGG portion of the repeat sequence via the histidine imidazole side chain, two deprotonated amide N-atoms, and a backbone carbonyl O-atom. Using appropriate selection criteria, we have generated a short list of candidate metal ions (Co3+, Ni2+, Pd2+, Pt2+) that can serve as potential surrogates for Cu2+. The selected metal ions were screened for binding interactions with the OR-derived peptide fragment AcHGGGWNH2 (Ac = acetyl, amino acid residues in italics) using electrospray ionization mass spectrometry. The coordination geometries of these metal ions with the synthetic OR peptide were subsequently determined from fragment analysis using collision-induced dissociation tandem mass spectrometry. Our results indicate that, although Co3+, Pd2+, and Pt2+ all bind to the OR fragment via the peptide backbone to varying extents, each of these metal ions appears to associate with the peptide in a unique manner, which is distinct from the way in which Cu2+ is coordinated. This work illustrates the extremely strong selectivity for Cu2+ of this highly conserved region of the mammalian prion protein.
authors.affiliation: Structural Biology Research Group, Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta, T2N 1N4, Canada.
authors.forename: M Jake
authors.initials: MJ
authors.lastname: Pushie
authors.forename: Andrew R S
authors.initials: AR
authors.lastname: Ross
authors.forename: Hans J
authors.initials: HJ
authors.lastname: Vogel
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002413:Cations, Divalent; D003035:Cobalt / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D003300:Copper / Q000737:chemistry / Q000378:metabolism*; D006639:Histidine / Q000737:chemistry; D007093:Imidazoles / Q000737:chemistry; D008969:Molecular Sequence Data; D009532:Nickel / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D010165:Palladium / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D010984:Platinum / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D011328:Prions / Q000032:analysis / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*
chemical_list: D002413:Cations, Divalent; D007093:Imidazoles; D011328:Prions; D003035:Cobalt; D010984:Platinum; D006639:Histidine; D010165:Palladium; D003300:Copper; D009532:Nickel