In recent years the chaperone Hsc-70 has become a target for drug design in anti-cancer therapies.  Recently X-Ray crystallography revealed that Hsc-70 has a potential allosteric pocket occupied by glycerol, which is located on the side of the molecule opposite the ATP/ADP binding cavity. Binding and docking experiments predicted that the glycerol-binding site is a promising target for Hsc-70 inhibition (Z. Zhang et al., Biochimie 108 (2015), 186-192).  We took further advantage of the discovery of Hsc-70’s new allosteric site to perform <i>in silico</i> screening of novel peptidic inhibitors, having as pharmacological scaffold dipeptides with hydroxyl and carboxyl groups from the series: XY-D-Asp-L-AHPPA-Y-CONH2; XY-D-Asp-L-Hyp(tBu)-CONH2; XY-[2,4-dichloro-D-Phe]-[4-(1-piperidine-4yl) butanoic acid-COOH], among other combinations of both natural and unnatural amino acids.  Both the hydroxyl and the carboxyl groups grafted at selected positions on the peptide backbone are expected to mimic the glycerol backbone that is stabilized by hydrogen bonding to Thr 149 in the glycerol binding pocket (Z. Zhang et al., Biochimie 108 (2015), 186-192).  AutoDockVina was used to perform rigid molecular docking of selected peptides in the glycerol binding pocket, using the Hsc-70 structure 4H5V.pdb as target protein. The compounds predicted to have free energies of interaction with Hsc-70 lower than “-9 kcal/mol” were further selected for enzymatic screening of their inhibition of Hsc-70 ATPase activity. The Hsc-70 ATP-ase kinetics analysis showed that some peptide inhibitors are shifting the hyperbolic behavior of the enzyme towards a sigmoidal (allosteric) shape, a shape characterized by an increased lag phase, especially as compared with the classical ATP-ase competitive inhibitors, and having inhibitory constants (Ki) in the low uM range.

Structure-based design, synthesis, and evaluation of novel peptides allosteric inhibitors of Hsc-70

251st National Meeting (2016)

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