Optimizing the Binding of OGT and a Peptidic Substrate Towards Pseudo-Substrate Inhibitors Via Molecular Dynamic Simulations

Elevated O -GlcNAcylation has been shown to be closely correlated with the occurrence and development of cancer, and inhibiting O -GlcNAc transferase (OGT) activity was demonstrated as a potential tumor treatment strategy. However, the development of pharmacological OGT inhibitors still faces challenges, such as low affinity and poor selectivity. Considering to OGT preferences for the sequence of its peptidic substrates, we herein integrated molecular dynamics simulation approaches to give deep insights into the binding behaviors between OGT and its peptidic substrate ZO3S1, and discussed the unfavorable inter-residue contacts inside the binding pocket, especially between H509 of OGT and S15 of the peptide, upon temperature increase. Removing this unfavorable contact from the peptide (ZO3S1 with S15A mutation) was shown to be able to increase its interaction with OGT, which was manifested by the enhanced OGT activity against this peptide. The pseudo-substrate peptide (ZO3S1 with S13A and S15A mutations) inhibited the activity of purified OGT with an IC 50 of 192.9 μM and it can also inhibit the total O -GlcNAcylation in cancer cell lines in a concentration-dependent manner. Our results provided useful models and basis for further rational optimization of selective OGT inhibitors based on the dynamic interactions of OGT and its peptidic substrates.