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Title: Ni K-Edge XAS Suggests that Coordination of Ni II to the Unstructured Amyloidogenice Region of the Human Prion Protein Produces a Ni2 bis-u-hydroxo Dimer

Abstract

Prion diseases are thought to be caused by the misfolding of the ubiquitous neuronal membrane prion protein (PrP) through an unknown mechanism that may involve Cu{sup II} coordination to the PrP. Previous work has utilized Ni{sup II} as a diamagnetic probe for Cu{sup II} coordination [C.E. Jones, M. Klewpatinond, S.R. Abdelraheim, D.R. Brown, J.H. Viles, J. Mol. Biol. 346 (2005) 1393-1407]. Herein we investigate Ni{sup II} coordination to the PrP fragment PrP(93-114) (AcN-GGTHSQWNKPSKPKTNMKHMAG) at pH = 10.0 by Ni K-edge X-ray absorption spectroscopy (XAS). We find that two equivalents of Ni{sup II} will coordinate to PrP(93-114) by UV/Vis titrations and mass spectrometry. Ni K-edge XAS data is consistent with Ni{sup II} ligated by five N/O based ligands (three N/O ligands at 2.01(2) {angstrom} and two at 1.855(2) {angstrom}). We were also able to locate a Ni-Ni vector at 3.1(1) {angstrom}, which suggests the two Ni{sup II} centers are contained in a bis-{mu}-hydroxo dimer. We therefore suggest that Ni{sup II} may not be a suitable diamagnetic mimic for Cu{sup II} coordination within the PrP since differential coordination modes for the two metals exist.

Authors:
;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
930292
Report Number(s):
BNL-80996-2008-JA
Journal ID: ISSN 0162-0134; JIBIDJ; TRN: US200822%%1452
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Inorganic Biochemistry; Journal Volume: 101; Journal Issue: 2
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; ABSORPTION SPECTROSCOPY; COORDINATES; DATA; DIMERS; DISEASES; HUMAN POPULATIONS; LIGANDS; MASS SPECTROSCOPY; MEMBRANES; METALS; PROBES; PROGRAMMING LANGUAGES; PROTEINS; VECTORS; national synchrotron light source

Citation Formats

Shearer,J., and Soh, P. Ni K-Edge XAS Suggests that Coordination of Ni II to the Unstructured Amyloidogenice Region of the Human Prion Protein Produces a Ni2 bis-u-hydroxo Dimer. United States: N. p., 2007. Web. doi:10.1016/j.jinorgbio.2006.09.032.
Shearer,J., & Soh, P. Ni K-Edge XAS Suggests that Coordination of Ni II to the Unstructured Amyloidogenice Region of the Human Prion Protein Produces a Ni2 bis-u-hydroxo Dimer. United States. doi:10.1016/j.jinorgbio.2006.09.032.
Shearer,J., and Soh, P. Mon . "Ni K-Edge XAS Suggests that Coordination of Ni II to the Unstructured Amyloidogenice Region of the Human Prion Protein Produces a Ni2 bis-u-hydroxo Dimer". United States. doi:10.1016/j.jinorgbio.2006.09.032.
@article{osti_930292,
title = {Ni K-Edge XAS Suggests that Coordination of Ni II to the Unstructured Amyloidogenice Region of the Human Prion Protein Produces a Ni2 bis-u-hydroxo Dimer},
author = {Shearer,J. and Soh, P.},
abstractNote = {Prion diseases are thought to be caused by the misfolding of the ubiquitous neuronal membrane prion protein (PrP) through an unknown mechanism that may involve Cu{sup II} coordination to the PrP. Previous work has utilized Ni{sup II} as a diamagnetic probe for Cu{sup II} coordination [C.E. Jones, M. Klewpatinond, S.R. Abdelraheim, D.R. Brown, J.H. Viles, J. Mol. Biol. 346 (2005) 1393-1407]. Herein we investigate Ni{sup II} coordination to the PrP fragment PrP(93-114) (AcN-GGTHSQWNKPSKPKTNMKHMAG) at pH = 10.0 by Ni K-edge X-ray absorption spectroscopy (XAS). We find that two equivalents of Ni{sup II} will coordinate to PrP(93-114) by UV/Vis titrations and mass spectrometry. Ni K-edge XAS data is consistent with Ni{sup II} ligated by five N/O based ligands (three N/O ligands at 2.01(2) {angstrom} and two at 1.855(2) {angstrom}). We were also able to locate a Ni-Ni vector at 3.1(1) {angstrom}, which suggests the two Ni{sup II} centers are contained in a bis-{mu}-hydroxo dimer. We therefore suggest that Ni{sup II} may not be a suitable diamagnetic mimic for Cu{sup II} coordination within the PrP since differential coordination modes for the two metals exist.},
doi = {10.1016/j.jinorgbio.2006.09.032},
journal = {Journal of Inorganic Biochemistry},
number = 2,
volume = 101,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • Prion diseases are caused by the misfolding and aggregation of the prion protein (PrP). Herein we provide evidence that the Cu{sup II} adduct of the unstructured amyloidogenic fragment of the human PrP (PrP(91-126)) is redox active under physiological conditions. We have identified that the relevant high-affinity Cu{sup II} binding region of PrP(91-126) is contained between residues 106 and 114. Both [Cu{sup II}(PrP(91-126))] and [Cu{sup II}(PrP(106-114))] have Cu{sup II} K{sub d} values of {approx}90 {mu}M. Furthermore, the smaller PrP fragment PrP(106-114) coordinates Cu{sup II} producing an electronic absorption spectrum nearly identical with [Cu{sup II}(PrP(91-126))] ({lambda}{sub max} {approx}610 nm ({var_epsilon} {approx}125 M{supmore » -1} cm{sup -1})) suggesting a similar coordination environment for Cu{sup II}. Cu K-edge X-ray absorption spectroscopy (XAS) reveals a nearly identical CuN(N/O){sub 2}S coordination environment for these two metallopeptides (2N/O at {approx}1.97 {angstrom}; 1S at {approx}2.30 {angstrom}; 1 imidazole N at {approx}1.95 {angstrom}). Both display quasireversible Cu{sup II}/Cu{sup I} redox couples at {approx}-350 mV vs Ag/AgCl. ESI-MS indicates that both peptides will coordinate Cu{sup I}. However, XAS indicates differential coordination environments between [Cu{sup I}(PrP(91-126))] and [Cu{sup I}(PrP(106-114))]. These data indicate that [Cu{sup I}(PrP(91-126))] contains Cu in a four coordinate (N/O){sub 2}S{sub 2} environment with similar (N/O)-Cu bond distances (Cu-(N/O) r = 2.048(4) {angstrom}), while [Cu{sup I}(PrP(106-114))] contains Cu in a four coordinate (N/O){sub 2}S{sub 2} environment with differential (N/O)-Cu bond distances (Cu-(N/O) r{sub 1} = 2.057(6) {angstrom}; r{sub 2} = 2.159(3) {angstrom}). Despite the differential coordination environments both Cu-metallopeptides will catalytically reduce O{sub 2} to O{sub 2}{sup {sm_bullet}-} at comparable rates.« less
  • The prion protein is a ubiquitous neuronal membrane protein. Misfolding of the prion protein has been implicated in transmissible spongiform encephalopathies (prion diseases). It has been demonstrated that the human prion protein (PrP) is capable of coordinating at least five Cu{sup II} ions under physiological conditions; four copper binding sites can be found in the octarepeat domain between residues 61 and 91, while another copper binding site can be found in the unstructured 'amyloidogenic' domain between residues 91 and 126 PrP(91-126). Herein we expand upon a previous study (J. Shearer, P. Soh, Inorg. Chem. 46 (2007) 710-719) where we demonstratedmore » that the physiologically relevant high affinity Cu{sup II} coordination site within PrP(91-126) is found between residues 106 and 114. It was shown that Cu{sup II} is contained within a square planar (N/O){sub 3}S coordination environment with one His imidazole ligand (H(111)) and one Met thioether ligand (either M(109) or M(112)). The identity of the Met thioether ligand was not identified in that study. In this study we perform a detailed investigation of the Cu{sup II} coordination environment within the PrP fragment containing residues 106-114 (PrP(106-114)) involving optical, X-ray absorption, EPR, and fluorescence spectroscopies in conjunction with electronic structure calculations. By using derivatives of PrP(106-114) with systematic Met {yields} Ile 'mutations' we show that the Cu{sup II} coordination environment within PrP(106-114) is actually comprised of a mixture of two major species; one CuII(N/O){sub 3}S center with the M(109) thioether coordinated to Cu{sup II} and another Cu{sup II}(N/O){sub 3}S center with the M(112) thioether coordinated to Cu{sup II}. Furthermore, deletion of one or more Met residues from the primary sequence of PrP(106-114) both reduces the Cu{sup II} affinity of the peptide by two to seven fold, and renders the resulting Cu{sup II} metallopeptides redox inactive. The biological implications of these findings are discussed.« less
  • The influence of a single octarepeat expansion on the Cu{sup II} and Zn{sup II} coordination environments within the octarepeat domain of the human prion protein is examined. Using X-ray absorption spectroscopy and diethyl pyrocarbonate labeling studies, we find that at low copper concentrations the 'normal' octarepeat domain (four PHGGGWGQ repeats) coordinates Zn{sup II} in an (N/O){sub 6} coordination environment with two histidine residues and Cu{sup II} in a redox-inactive (N/O){sub 4} coordination environment using one imidazole residue. Expansion of the octarepeat region by one repeat (five PHGGGWGQ repeats) yields a three-histidine (N/O){sub 6} coordination environment for Zn{sup II} and amore » two-histidine (N/O){sub 4} coordination environment for Cu{sup II} at low copper concentrations. This Cu{sup II}[(N/O){sub 2}-histidine{sub 2}] coordination motif is redox-active and capable of generating H{sub 2}O{sub 2} under reducing aerobic conditions.« less
  • To explore Cu(II) ion coordination by His{sup 186} in the C-terminal domain of full-length prion protein (moPrP), we utilized the magnetic dipolar interaction between a paramagnetic metal, Cu(II) ion, and a spin probe introduced in the neighborhood of the postulated binding site by the spin labeling technique (SDSL technique). Six moPrP mutants, moPrP(D143C), moPrP(Y148C), moPrP(E151C), moPrP(Y156C), moPrP(T189C), and moPrP(Y156C,H186A), were reacted with a methane thiosulfonate spin probe and a nitroxide residue (R1) was created in the binding site of each one. Line broadening of the ESR spectra was induced in the presence of Cu(II) ions in moPrP(Y148R1), moPrP(Y151R1), moPrP(Y156R1), andmore » moPrP(T189R1) but not moPrP(D143R1). This line broadening indicated the presence of electron-electron dipolar interaction between Cu(II) and the nitroxide spin probe, suggesting that each interspin distance was within 20 A. The interspin distance ranges between Cu(II) and the spin probes of moPrP(Y148R1), moPrP(Y151R1), moPrP(Y156R1), and moPrP(T189R1) were estimated to be 12.1 A, 18.1 A, 10.7 A, and 8.4 A, respectively. In moPrP(Y156R1,H186A), line broadening between Cu(II) and the spin probe was not observed. These results suggest that a novel Cu(II) binding site is involved in His186 in the Helix2 region of the C-terminal domain of moPrP{sup C}.« less