Isolation and characterization of a polymerized prion protein.

A polymerized form of recombinant mouse prion protein (mPrP) domain 23-231 [mPrP-(23-231)], designated mPrP-z, was generated at acidic pH (pH 2-5) in the presence of selected concentrations of denaturant (2 M guanidinium chloride or 5 M urea). This isoform of mPrP is stable in acidic solution after removal of denaturant. It can be isolated and purified using reversed-phase HPLC or size-exclusion HPLC. mPrP-z bears structural properties that partially resemble those of scrapie prion. Unlike the native mPrP-(23-231) (mPrP-N), mPrP-z exhibits a high content of beta-sheet structure, as shown by CD spectroscopy, and exists as an oligomer with an approximate molecular mass of 340000 Da, as measured by light scattering. However, similarly to mPrP-N, mPrP-z contains the intact disulphide bond and is sensitive to digestion by proteinase K.