FIGURE 2.

Transmission of prion state to a divergent protein. Large ellipse on the left represents yeast cell. Gray area represents the cellular compartment or quality control protein deposit containing aggregating proteins. Dotted ellipse indicates the specific interacting protein molecules that are considered in more detail and at larger magnification in the images to the right. Nonprion form of heterologous Sup35 prion domain protein is represented as unstructured black tangle while prion polymers are shown by light (orange) (pre-existing “donor” prion) or dark (the newly formed heterologous prion) pleated lines demonstrating in-register parallel β-sheet architecture. Short crosscut lines indicate positions of interactions between β-sheets. Prion domains with high identity of amino acid sequences in the regions, corresponding to the cross-β core of a donor protein, can convert each other to prion form with high frequency, while prion proteins with lower identity typically cannot adopt the donor strain conformation and form nonprion aggregates; however, in rare cases, the recipient protein is converted to a prion conformation, that is only partly collinear to the original donor conformation, and partly different from it.