Arginine 469 is a pivotal residue for the Hsc70–GlcNAc-binding property

The members of the 70 kDa-heat shock proteins (HSP70) family play numerous fundamental functions in the cell such as promoting the assembly of multimeric complexes or helping the correct folding of nascent proteins to take place. In numerous previous studies we demonstrated that Hsp70 and its constitutive isoform Hsc70 are endowed of a GlcNAc-binding activity. The molecular modeling of the substrate binding domain of Hsc70 and in silico docking experiments using Ser/Thr-O-GlcNAc motifs allowed to define the potential carbohydrate-recognition region and to point out the crucial position of Arg469 as an amino-acid directly interacting with the sugar moiety. We cloned a flagged Hsc70 in a pCMV.SPORT6 vector and we showed that the mutation R469A decreased the GlcNAc-binding property of the chaperone of around 70%. This is the first work reporting the localization of the GlcNAc-binding domain of a member of the HSP70 family.

Research highlights► Hsc70 interacts with GlcNAc moieties through its substrate binding domain. ► The Arginine 469 is a key residue involved in the interaction between Hsc70 and the GlcNAc residue. ► The mutant Hsc70 R469A displays only 30% of GlcNAc-binding property when compared to the wild type form. ► The cytosolic binomial OGT/Hsc70 might be similar to the reticular binomial calreticulin/UGGT.