Schematic representation of PK-resistant fragments in rPrP^Sc corresponding to Type 1 (MM1) and Type 2 (MM2) sCJD prions and molecular characteristics of purified human rPrPSc used in structural studies.

(a) Outline of classification of Type 1 and Type 2 human prions based on proteolytic fragmentation of PrP^Sc [5,52]. Major cleavage sites by PK are indicated by arrows; GLP—glycolipid; CHO- complex N-glycosylation chains. The codes above light blue brackets represent monoclonal antibodies used in differentiation of various domains of human prions, and the numbers below these brackets indicate linear epitopes recognized by these antibodies. (b) Distinct glycosylation patterns and electrophoretic mobilities of purified human Type 1 (MM1) and Type 2 (MM2) sCJD rPrP^Sc (homozygous for methionine (M) in codon 129) used in structural studies. To differentiate Type 1, Type 2 prions, and their C-terminal fragments, Western blots of purified rPrP^Sc (fraction 8; F8) from the brain homogenate (BH) of type MM1 and MM2 sCJD were developed with mAb 12B2 (epitope residues 89–93) [53], mAb 3F4 (epitope residues 107–112) [54], and rabbit polyclonal antibody 2301 (epitope residues 220–231) [55]. The lower panels correspond to prolonged exposure of the same WB to detect less abundant low molecular weight fragments of rPrP^Sc. (c) Distinct fragmentation patterns of purified MM1 and MM2 sCJD prions in silver stained SDS-PAGE before and after deglycosylation with PNGase F. The symbols (*) and (#) indicate bands corresponding to PK and PNGase F, respectively. The molecular weights of marker proteins are in kDa.