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Studies on the effect of the J-domain on the substrate binding domain (SBD) of Hsp70 using a chimeric human J-SBD polypeptide

Tiroli-Cepeda, Ana O.; Seraphim, Thiago V.; Pinheiro, Glaucia M. S.; Souto, Denio E. P.; Kubota, Lauro T.; Borges, Júlio C.; Barbosa, Leandro R. S.; Ramos, Carlos H. I.

By 12 March 2019No Comments

International Journal of Biological Macromolecules, 2019, vol 124pp. 111-120



DnaJ/Hsp40 chaperones deliver unfolded proteins and stimulate the ATPase activity of DnaK/Hsp70 via their J-domain. However, the interaction is transient, creating a challenge for detailed analysis. We investigated whether it would be possible to gain further understanding of this interaction by engineering a chimeric polypeptide where the J-domain of Hsp40 was covalently attached to the substrate binding domain (SBD) of Hsp70 by a flexible linker. The rationale is to increase the proximity between the interacting partners to promote their natural interaction and facilitate the characterization of the interaction. The resulting chimera, termed J-SBD, was properly folded and had properties not present in the full-length Hsp70 or in the SBD alone, for instance a higher protective effect against aggregation and being a monomer. Substrate binding also appear to exceed that of SBD alone as revealed by a decreased binding to bis-ANS, a probe for hydrophobic patches. This hypothesis is supported by the structural model created by small angle X-ray scattering, suggesting that the lid subdomain (SBDα) is partially opened in the J-SBD. Collectively, our results suggest a model in which J-domain binding may shift the Hsp70 equilibrium towards the monomer state, exposing hydrophobic sites prone to substrate accommodation.

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