Three-state dynamics of zinc(II) complexes yielding significant antidiabetic targets

Abstract

Protein Tyrosine Phosphatase 1B (PTP1B), being negative regulator of insulin signaling pathways is considered as potential medicinal target. Selective and targeted inhibitors for PTP1B can impact the therapeutic options available to cure chronic illness such as diabetes. Significant research evidence including computational studies on the role of Zn²⁺ in binding and inhibiting the catalytic pocket have been reported along with experimental exploration of zinc(II) complexes as potent inhibitors of the enzyme. The current study has employed advanced computational methods to explore the binding and conformational orientation of zinc(II) complexes in the active site of apoenzyme, phosphoenzyme, and TSA 2 of PTP1B. Metal ion modeling was performed for zinc metal center (Zn-OOOO) utilizing a Python based Metal Center Parameter Builder (MCPB.py). The findings of the study suggest that zinc(II) complex binds to structurally and functionally important residues in open and closed conformation as well as in the phosphorylated state of the enzyme. It was observed that when the catalytic cysteine is phosphorylated in a closed conformation, the zinc(II) complex forms significant interactions with PHE182, VAL184, GLY183, and PRO180 while pushing away Q-loop GLN262 which is crucial for the hydrolysis of phosphoenzyme. Subsequently, the reported inhibitor has also demonstrated its potential to function as allosteric modulator of the enzyme occupying catalytic WPD loop residues. The study uncovers putative binding sites of zinc-containing drugs and gives insight into the size and design of such compounds which keeps them accessible and anchored in the vicinity of active site residues. Reported inhibitor offers enhanced selectivity and inhibition in all three states of the enzyme in contrast to zinc ions which can only impede enzyme in the phosphorylated state. In addition to this, investigation of ASP265→GLU265 mutation reveals the role of GLU265 in affecting the flexibility of WPD loop residues highlighting it as loss-of-function mutation. Our results hints towards a metallodrug approach that builds on the research evidence of inhibition effects of Zn²⁺ in the binding pocket of PTP1B. The findings presented are noteworthy, not just due to their significant relevance for clinical application, but also for the design and synthesis of novel zinc(II) complexes.

Keywords: Molecular docking; Protein tyrosine phosphatase; Simulations; metal complexes.