Understanding domain movements and interactions of Pseudomonas aeruginosa lipase with lipid molecule tristearoyl glycerol: A molecular dynamics approach.

Lipases are biocatalysts which exhibit optimal activity at the aqueous-lipid interface. Molecular Dynamics (MD) Simulation studies on lipases have revealed the structural changes occurring in the enzyme, at the loop-helix-loop, often designated as the "lid", which is responsible for its interfacial activation. In recent years, MD simulation of lipases at molecular level have been studied in detail, whereas very few studies are carried over on its interaction with lipid molecules. Hence, in the current study we have investigated molecular interaction of bacterial lipase (Pseudomonas aeruginosa lipase, PAL) with a lipid molecule (tristearoyl glycerol, TGL). This provides an insight into the interfacial activation of the enzyme. The lipid molecule was placed near the lids of the enzyme and MD simulations were performed for 100 ns to understand the nature and site of the interaction. The results clearly indicate that, the presence of a lipid molecule near the lids affects the motion of the enzyme through changes in conformation. Lipid molecule near the lids reduces the movements of both lids, and the TGL molecule was observed moving towards the active site. The movement of the lids, surface accessibility and the domain movements of PAL are discussed and the results provide valuable insight in to the role played by the two lids in the interfacial activation of PAL with TGL.

p53 mediates impaired insulin signaling in 3T3-L1 adipocytes during hyperinsulinemia.

Hyperinsulinemia is being implicated in the development of insulin resistance but remains poorly understood. The present study focuses on p53-mediated impaired insulin signaling by hyperinsulinemia in 3T3-L1 adipocytes. Hyperinsulinemia impairs insulin-stimulated glucose uptake and its cellular signaling in a dose- and time-dependent manner. An increased level of reactive oxygen species (ROS) and stress response signals were observed, and quenching of the ROS by an antioxidant N-acetylcysteine (NAC) did not revert impaired insulin sensitivity. The tumor suppressor p53 has emerged as a crucial factor in the metabolic adaptation of cancer cells under nutritional starvation and is being studied in the development of insulin resistance in adipocytes at physiological level. Interestingly, we observed hyperinsulinemia-enhanced p53 level in a time-dependent manner without exhibiting cytotoxicity. Transient knockdown of p53 partially improved insulin sensitivity revealing a novel link between p53 and insulin signaling in adipocytes. The findings suggest that hyperinsulinemia-induced p53 impairs insulin sensitivity in 3T3-L1 adipocytes.

Molecular dynamics approach to probe the allosteric inhibition of PTP1B by chlorogenic and cichoric acid.

Protein tyrosine phosphatase 1B (PTP1B), a major negative regulator of the insulin and leptin signaling pathway, is a potential target for therapeutic intervention against diabetes and obesity. The recent discovery of an allosteric site in PTP1B has created an alternate strategy in the development of PTP1B targeted therapy. The current study investigates the molecular interactions between the allosteric site of PTP1B with two caffeoyl derivatives, chlorogenic acid (CGA) and cichoric acid (CHA), using computational strategies. Molecular docking analysis with CGA and CHA at the allosteric site of PTP1B were performed and the resulting protein-ligand complexes used for molecular dynamics simulation studies for a time scale of 10 ns. Results show stable binding of CGA and CHA at the allosteric site of PTP1B. The flexibility of the WPD loop was observed to be constrained by CGA and CHA in the open (inactive), providing molecular mechanism of allosteric inhibition. The allosteric inhibition of CGA and CHA of PTP1B was shown to be favorable due to no restriction by the α-7 helix in the binding of CGA and CHA at the allosteric binding site. In conclusion, our results exhibit an inhibitory pattern of CGA and CHA against PTP1B through potent binding at the allosteric site.