Structural Insights into the Chaperone Activity of the 40-kDa Heat Shock Protein DnaJ: BINDING AND REMODELING OF A NATIVE SUBSTRATE

Jorge Cuéllar,Judit Perales-Calvo,Arturo Muga,José María Valpuesta,Fernando Moro

doi:10.1074/jbc.m112.430595

Jorge Cuéllar, Judit Perales-Calvo + Show 3 more

Open Access

https://doi.org/10.1074/jbc.m112.430595

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Abstract

Hsp40 chaperones bind and transfer substrate proteins to Hsp70s and regulate their ATPase activity. The interaction of Hsp40s with native proteins modifies their structure and function. A good model for this function is DnaJ, the bacterial Hsp40 that interacts with RepE, the repressor/activator of plasmid F replication, and together with DnaK regulates its function. We characterize here the structure of the DnaJ-RepE complex by electron microscopy, the first described structure of a complex between an Hsp40 and a client protein. The comparison of the complexes of DnaJ with two RepE mutants reveals an intrinsic plasticity of the DnaJ dimer that allows the chaperone to adapt to different substrates. We also show that DnaJ induces conformational changes in dimeric RepE, which increase the intermonomeric distance and remodel both RepE domains enhancing its affinity for DNA.

Highlights

DnaJ is an Hsp40 molecular chaperone able to bind and remodel native substrates as RepE, the repressor/ activator of plasmid F replication
We show that DnaJ induces conformational changes in dimeric RepE, which increase the intermonomeric distance and remodel both RepE domains enhancing its affinity for DNA
Using electron microscopy (EM) and other biochemical and biophysical techniques, we show that DnaJ induces a conformational change in the RepE dimer that

Summary

Background

DnaJ is an Hsp molecular chaperone able to bind and remodel native substrates as RepE, the repressor/ activator of plasmid F replication. DnaJ enhances the ATPase activity of DnaK, the major bacterial Hsp, synergistically with substrates This function relies on the highly conserved N-terminal domain of DnaJ, the J-domain, which interacts with the nucleotide-bind-. Ing domain of DnaK [4] In addition to this cochaperone function, DnaJ and Ydj1p, its yeast homolog, can behave as independent chaperones, exhibiting a “holdase” activity that allows their interaction with unfolded polypeptides preventing their aggregation [5, 6]. Substitution of the residues that form the binding site severely affects peptide binding, refolding of denatured substrates and cell viability [14, 15] On this basis, Hsp proteins may have a large and adaptable interaction surface formed by several domains to accommodate different protein substrates. We show that DnaJ displays a conformational plasticity that may be important to adapt to different substrate proteins

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