Identification of a homology-independent linchpin domain controlling mouse and bank vole prion protein conversion

Prions are unorthodox pathogens that cause fatal neurodegenerative diseases in humans and other mammals. Prion propagation occurs through the self-templating of the pathogenic conformer PrP(Sc), onto the cell-expressed conformer, PrP(C). Here we study the conversion of PrP(C) to PrP(Sc) using a recombinant mouse PrP(Sc) conformer (mouse protein-only recPrP(Sc)) as a unique tool that can convert bank vole but not mouse PrP(C) substrates in vitro. Thus, its templating ability is not dependent on sequence homology with the substrate. In the present study, we used chimeric bank vole/mouse PrP(C) substrates to systematically determine the domain that allows for conversion by Mo protein-only recPrP(Sc). Our results show that that either the presence of the bank vole amino acid residues E227 and S230 or the absence of the second N-linked glycan are sufficient to allow PrP(C) substrates to be converted by Mo protein-only recPrP(Sc) and several native infectious prion strains. We propose that residues 227 and 230 and the second glycan are part of a C-terminal domain that acts as a linchpin for bank vole and mouse prion conversion.