... within the C-terminal domain of Ure2p that interacts with Ssa1p. Because the C-termi-nal domain of Ure2p is tightly involved in the assembly of the prion into fibrils [25–28] and because Ssa1p sequesters ... His-Tagged Ssa1p (B). (A) A mixture of untreated Ure2p and Ssa1p (lane 1); Ure2p alone(lanes 2, 5, 8 and 11), Ssa1p alone (lanes 3, 6, 9 and 12), and Ure2p incubated in presence of Ssa1p (lanes ... 10. Ure2p, Ssa1p and Ure2p incubated with Ssa1p treated with BS2G are seen in lanes 1 and 8, 4 and 11 and 6 and 13, respectively. Similar samples treated with BS3 are seen inlanes 2 and 9, 5 and...