Autorepression of Yeast Hsp70 co-chaperones by intramolecular interactions involving their J-domains.

Abstract

The Hsp70 chaperones control protein homeostasis in all ATP-containing cellular compartments. J-domain proteins (JDPs) co-evolved with Hsp70s to trigger ATP-hydrolysis and catalytically upload various substrate polypeptides in need to be structurally modified by the chaperone. Here, we measured the protein disaggregation and refolding activities of the main yeast cytosolic Hsp70, Ssa1, in the presence of its most abundant JDPs, Sis1 and Ydj1, and two swap mutants, in which the J-domains have been interchanged. The observed differences by which the four constructs differently cooperate with Ssa1 and cooperate with each other, as well as their observed intrinsic ability to bind misfolded substrates and trigger Ssa1s ATPase, indicates the presence of yet uncharacterized intra-molecular dynamic interactions between the J-domains and their remaining C-terminal domains. Taken together, the data suggest an auto-regulatory role to these intra-molecular interactions within both type A and B JDPs, which might have evolved to reduce energy-costly ATPase cycles by the Ssa1-4 chaperones that are the most abundant Hsp70s in the yeast cytosol. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=148 SRC="FIGDIR/small/578849v1_figa1.gif" ALT="Figure 1"> View larger version (38K): org.highwire.dtl.DTLVardef@d895d3org.highwire.dtl.DTLVardef@1545221org.highwire.dtl.DTLVardef@dc08b3org.highwire.dtl.DTLVardef@1bf286a_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical abstract:C_FLOATNO Lower panel: autoinhibited DnaJA or DnaJB dimers, drawn here as Swiss army knives with sequestered J-domains as folded blades, can bind misfolded polypeptides (violet). Upper panel: DnaJA or DnaJB become active when their J-domains are exposed and can bind ATP-Hsp70s, and transfer the misfolded polypeptides, respectively, onto Hsp70s nucleotide binding (Cyan) and protein binding domains (Orange and Green). Hsp70s interdomain linker (DLLLLDV, Magenta). C_FIG