Over the past two decades, covalent inhibitors have gained much interest and are living up to their reputation as a powerful tool in drug discovery. Covalent inhibitors possess several significant advantages, including increased biochemical efficiency, prolonged duration and the ability to target shallow,
solvent-exposed substrate-binding domains. One of the
enzymes that have been both covalently and non-covalently targeted is the
heat shock protein 72 (HSP72). This elevated
enzyme expression in
cancer cells may be responsible for
tumorigenesis and
tumor progression by providing
chemotherapy resistance. A critical gap remains in the molecular understanding of the structural mechanism's covalent and non-covalent binding to HSP72. In this study, we explore the most optimal binding mechanism in the inhibition of the HSP72. Based on the molecular dynamic analyses, it was evident that the non-covalent complex showed more stability than the covalent complex. The covalent
ligand, however, was more able to induce and stabilize the sealed conformation of the HSP72-NBD
ATP binding domain throughout the. Also, the non-covalent
ligand does not induce any significant conformational change as it remained close to the shape of the unbound complex; and the affinity is only dependent on the multiple hydrogen bonds in contrast to the covalent
ligand. This is supported by the secondary structure elements and principal component analysis that was more dominant in the covalently inhibited complex. Covalent bond induced the α-helices sealed conformation of the HSP72-NBD; based on our findings, this will prevent other small molecules from interacting at the
ATP binding site domain. Moreover, inhibition of the
ATP binding domain can directly affect the ATPs protein folding mechanism of the HSP72
enzyme. The essential dynamic analysis presented in this report compliments the binding mechanism of HSP72, establishing covalent inhibition as the preferred method of inhibiting the
HSP72 protein. The findings from this study may assist in the design of more target-specific HSP72 covalent inhibitors exploring the surface-exposed
lysine residues.