Small Heat Shock Proteins Potentiate Amyloid Dissolution by Protein Disaggregases from Yeast and Humans
Sup35 is composed of a C-terminal GTPase domain (amino acids 254–685, black) that confers translation termination activity, a highly charged middle domain (M, amino acids 124–253, dark grey), and a prionogenic N-terminal domain (N, amino acids 1–123, light grey) enriched in glutamine, asparagine, tyrosine, and glycine. Together N and M (NM) confer all the properties needed to form a stable prion in yeast . Hence, NM is termed the prion domain. Within N, prion recognition elements termed the “Head” (red) and “Tail” (green), which flank a “Central Core” (blue), play important roles in prionogenesis. After a lag phase (steps 1–3), Sup35 prions assemble rapidly (steps 4 and 5). Prion recognition elements within N make homotypic intermolecular contacts such that Sup35 prions are maintained by an alternating sequence of Head-to-Head (red) and Tail-to-Tail (green) contacts. The Central Core (blue) is sequestered by intramolecular contacts. The amino acids that comprise the Head, Core, and Tail region when NM is assembled at 25°C are indicated. The steps antagonized by Hsp26 and Hsp42 are indicated.