Narrow Results

Protein tyrosine phosphatase 1B (PTP1B) is one of the important regulators of signal transduction pathways. The present study aims to investigate the effect of Arg 221 on the active site of PTP1B. Six mutants were carried out using Schrödinger Suite 2007 and molecular dynamics simulation was performed by using the Tinker package. Results show that point mutations at position 221 have great influence on shape of active site, backbone movement of active site, and interaction between substrate and PTP1B. R221H and R221K lead to increased total interaction energies. R221G, R221F and R221T cause increase in total interaction energies, but decrease in interaction energies between pTyr 4 and P loop (catalytic residues). R221E results in both decreased total interaction energies and interaction energies between pTyr 4 and P loop. This indicates that Arg 221 mutated to basic residues can lead to enhanced binding affinity between substrate and protein; when mutated to acidic residues it will decrease binding affinity and catalytic activity; other kinds of mutations result in increased binding affinity but decreased catalytic activity.

Protein tyrosine phosphorylation is a post-translational modification mechanism, crucial for the regulation of nearly all aspects of cell life. This dynamic, reversible process is regulated by the balanced opposing activity of protein tyrosine kinases and protein tyrosine phosphatases. In particular, the protein tyrosine phosphatase 1B (PTP1B) is implicated in the regulation of the insulin-receptor activity, leptin-stimulated signal transduction pathways and other clinically relevant metabolic routes, and it has been found overexpressed or overregulated in human breasts, colon and ovary cancers. The WPD loop of the enzyme presents an inherent flexibility, and it plays a fundamental role in the enzymatic catalysis, turning it into a potential target in the design of new efficient PTP1B inhibitors. In order to determine the interactions that control the spatial conformation adopted by the WPD loop, complexes between the enzyme and halide ions (Br^- and I^- in particular) were crystallized and their crystallographic structure determined, and the collective movements of the aforementioned complexes were studied through Molecular Dynamics (MD) simulations. Both studies yielded concordant results, indicating the existence of a relationship between the identity of the ion present in the complex and the strength of the interactions it establishes with the surrounding protein residues.