Increasing Prion Propensity by Hydrophobic Insertion
Figure 6
Aromatic residues are not required in the Sup35 nucleation domain.
(A) The five tyrosines in the Sup35 nucleation domain (amino acids 1–40) were replaced with either leucines, isoleucines or valines. Strains were transformed either with an empty vector (left) or with a plasmid expressing the matching Sup35 mutant under control of the GAL1 promoter (right). All strains were cultured for three days in galactose/raffinose dropout medium, and then 10-fold serial dilutions were plated onto medium lacking adenine to select for [PSI+]. (B–E) Stability and curability of the Ade+ phenotype in cells expressing wild-type Sup35 (B), or Sup35 in which the five tyrosines in the nucleation domain were replaced with leucine (C), valine (D) or isoleucine (E). For each mutant, eight individual Ade+ isolates were grown on YPD (−) and YPD plus 4 mM guanidine HCl (+). Cells were then restreaked onto YPD to test for loss of the Ade+ phenotype.