title: Charge neutralization of the central lysine cluster in prion protein (PrP) promotes PrP(Sc)-like folding of recombinant PrP amyloids.
abstract: The structure of the infectious form of prion protein, PrP(Sc), remains unclear. Most pure recombinant prion protein (PrP) amyloids generated in vitro are not infectious and lack the extent of the protease-resistant core and solvent exclusion of infectious PrP(Sc), especially within residues ∼90-160. Polyanionic cofactors can enhance infectivity and PrP(Sc)-like characteristics of such fibrils, but the mechanism of this enhancement is unknown. In considering structural models of PrP(Sc) multimers, we identified an obstacle to tight packing that might be overcome with polyanionic cofactors, namely, electrostatic repulsion between four closely spaced cationic lysines within a central lysine cluster of residues 101-110. For example, in our parallel in-register intermolecular β-sheet model of PrP(Sc), not only would these lysines be clustered within the 101-110 region of the primary sequence, but they would have intermolecular spacings of only ∼4.8 Å between stacked β-strands. We have now performed molecular dynamics simulations predicting that neutralization of the charges on these lysine residues would allow more stable parallel in-register packing in this region. We also show empirically that substitution of these clustered lysine residues with alanines or asparagines results in recombinant PrP amyloid fibrils with extended proteinase-K resistant β-sheet cores and infrared spectra that are more reminiscent of bona fide PrP(Sc). These findings indicate that charge neutralization at the central lysine cluster is critical for the folding and tight packing of N-proximal residues within PrP amyloid fibrils. This charge neutralization may be a key aspect of the mechanism by which anionic cofactors promote PrP(Sc) formation.
authors.affiliation: From the Laboratory of Persistent Viral Diseases and.
authors.forename: Bradley R
authors.initials: BR
authors.lastname: Groveman
authors.affiliation: From the Laboratory of Persistent Viral Diseases and.
authors.forename: Allison
authors.initials: A
authors.lastname: Kraus
authors.affiliation: From the Laboratory of Persistent Viral Diseases and.
authors.forename: Lynne D
authors.initials: LD
authors.lastname: Raymond
authors.affiliation: the Computational Biology Section, Bioinformatics and Computational Biosciences Branch, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Dolan
authors.affiliation: From the Laboratory of Persistent Viral Diseases and.
authors.forename: Kelsie J
authors.initials: KJ
authors.lastname: Anson
authors.affiliation: the Research Technologies Branch, Microscopy Unit, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana 59840 and.
authors.forename: David W
authors.initials: DW
authors.lastname: Dorward
authors.affiliation: From the Laboratory of Persistent Viral Diseases and bcaughey@nih.gov.
authors.forename: Byron
authors.initials: B
authors.lastname: Caughey
mesh_terms: D000682:Amyloid / Q000737:chemistry* / Q000648:ultrastructure; D000818:Animals; D006801:Humans; D008239:Lysine / Q000737:chemistry*; D008647:Mesocricetus; D056004:Molecular Dynamics Simulation; D016296:Mutagenesis; D000071228:Polyelectrolytes; D011108:Polymers / Q000737:chemistry; D018620:PrPSc Proteins / Q000737:chemistry* / Q000235:genetics / Q000648:ultrastructure; D017096:Prion Diseases / Q000209:etiology / Q000378:metabolism* / Q000473:pathology; D011487:Protein Conformation; D017510:Protein Folding; D055503:Protein Multimerization; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000648:ultrastructure; D055672:Static Electricity
chemical_list: D000682:Amyloid; D008239:Lysine; D000071228:Polyelectrolytes; D011108:Polymers; D018620:PrPSc Proteins; D011994:Recombinant Proteins
keywords: Amyloid; Mutagenesis; Prion; Prion Disease; Protein Folding; Protein Structure