Copper and zinc promote interactions between membrane-anchored peptides of the metal binding domain of the prion protein.
The prion protein (PrP) has been identified as a metalloprotein capable of binding multiple copper ions and possibly zinc. Recent studies now indicate that prion self-recognition may be an important factor in both the normal function and misfunction of this protein. We have developed fluorescently labeled models of the prion protein that allow prion-prion interactions and metal binding to be investigated on the molecular level. Peptides encompassing the full metal binding region were anchored to the surface of small unilamellar vesicles, and PrP-PrP interactions were monitored by fluorescence spectroscopy as a function of added metal. Both Cu2+ and Zn2+ were found to cause an increase in the level of PrP-PrP interactions, by 117 and 300%, respectively, whereas other metals such as Ni2+, Co2+, and Ca2+ had no effect. The binding of either of these cofactors appears to act as a switch that induces PrP-PrP interactions in a reversible manner. Both glutamine and tryptophan residues, which occur frequently in the metal binding region of PrP, were found to be important in mediating PrP-PrP interactions. Experiments demonstrate that tryptophan residues are also responsible for the low level of PrP-PrP interactions observed in the absence of Cu2+ and Zn2+, and this is further supported by molecular modeling. Overall, our results indicate that PrP may be a bifunctional molecule capable of responding to fluctuations in both neuronal Cu2+ and Zn2+ levels.
Kenward
Angela G
AG
Department of Chemistry, East Carolina University, Greenville, North Carolina 27858, USA.
Bartolotti
Libero J
LJ
Burns
Colin S
CS
D000595:Amino Acid Sequence; D001665:Binding Sites; D003198:Computer Simulation; D003300:Copper / Q000737:chemistry* / Q000378:metabolism; D018360:Crystallography, X-Ray; D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry; D018698:Glutamic Acid / Q000737:chemistry / Q000378:metabolism; D008081:Liposomes; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism*; D011328:Prions / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D011721:Pyrenes / Q000737:chemistry; D012997:Solvents / Q000737:chemistry; D013050:Spectrometry, Fluorescence; D055672:Static Electricity; D014364:Tryptophan / Q000737:chemistry / Q000378:metabolism; D014867:Water / Q000737:chemistry; D015032:Zinc / Q000737:chemistry* / Q000378:metabolism
D008081:Liposomes; D010446:Peptide Fragments; D011328:Prions; D011721:Pyrenes; D012997:Solvents; D014867:Water; C002218:1-pyrenebutyrate; D018698:Glutamic Acid; D003300:Copper; D014364:Tryptophan; D015032:Zinc; D004134:Dimyristoylphosphatidylcholine