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. 2015 Jun 25;9(3):174–183. doi: 10.1080/19336896.2015.1027856

Figure 2.

Figure 2.

Prion propagation by the disaggregation machinery requires Hsp40 (J-protein). (A) To determine if E. coli DnaK (green circle) requires interaction with a yeast Hsp40 (triangles), DnaK with a mutation (red x, DnaK*) that specifically disrupts interaction with J-proteins, was expressed with ClpB and GrpE (BK*E) in cells lacking chromosomal Hsp104 (hsp104Δ). Loss of ability of BK*E to propagate prions shows an unknown Hsp40 (?) must be cooperating with BKE to promote prion replication. (B) In order to identify which yeast Hsp40 is involved, a compensatory mutation in J-proteins (red +) that restores interaction with DnaK* was made in yeast Hsp40s Sis1, Ydj1 and the E. coli Hsp40 DnaJ (indicated Sis1*, Ydj1* and DnaJ*, respectively). The compensatory mutations direct the interaction of these mutants with DnaK* even in the presence of wild type versions of the endogenous Hsp70s (circles) and Hsp40s (triangles). Each Hsp40 mutant was expressed separately with BK*E in hsp104Δ cells. Only Sis1* cooperates with BK*E to restore prion replication. Medium shown allows growth only if cells propagate prions.