Prion disease susceptibility is affected by beta-structure folding propensity and local side-chain interactions in PrP.
Prion diseases occur when the normally α-helical prion protein (PrP) converts to a pathological β-structured state with prion infectivity (PrP(Sc)). Exposure to PrP(Sc) from other mammals can catalyze this conversion. Evidence from experimental and accidental transmission of prions suggests that mammals vary in their prion disease susceptibility: Hamsters and mice show relatively high susceptibility, whereas rabbits, horses, and dogs show low susceptibility. Using a novel approach to quantify conformational states of PrP by circular dichroism (CD), we find that prion susceptibility tracks with the intrinsic propensity of mammalian PrP to convert from the native, α-helical state to a cytotoxic β-structured state, which exists in a monomer-octamer equilibrium. It has been controversial whether β-structured monomers exist at acidic pH; sedimentation equilibrium and dual-wavelength CD evidence is presented for an equilibrium between a β-structured monomer and octamer in some acidic pH conditions. Our X-ray crystallographic structure of rabbit PrP has identified a key helix-capping motif implicated in the low prion disease susceptibility of rabbits. Removal of this capping motif increases the β-structure folding propensity of rabbit PrP to match that of PrP from mouse, a species more susceptible to prion disease.
Campbell Family Institute for Cancer Research, Department of Biochemistry, University of Toronto, Toronto Medical Discovery Tower 4-307, 101 College Street, Toronto, ON, Canada M5G 1L7.
M Qasim
MQ
Khan
Braden
B
Sweeting
Vikram Khipple
VK
Mulligan
Pharhad Eli
PE
Arslan
Neil R
NR
Cashman
Emil F
EF
Pai
Avijit
A
Chakrabartty
D020816:Amino Acid Motifs; D000596:Amino Acids / Q000378:metabolism*; D000818:Animals; D016923:Cell Death / Q000187:drug effects; D002942:Circular Dichroism; D018360:Crystallography, X-Ray; D004198:Disease Susceptibility; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D017096:Prion Diseases / Q000378:metabolism*; D011328:Prions / Q000737:chemistry* / Q000378:metabolism* / Q000633:toxicity; D011485:Protein Binding / Q000187:drug effects; D011489:Protein Denaturation / Q000187:drug effects; D017510:Protein Folding / Q000187:drug effects; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D014508:Urea / Q000494:pharmacology
D000596:Amino Acids; D011328:Prions; D014508:Urea