Structural Studies of Nmda Receptor and Xanthine Oxidase Enzyme

Abstract

The first part of the thesis deals with the structural studies of N-Methyl-D-Aspartate receptors (NMDARs). NMDARs are ionotropic ligand-gated receptors that have pivotal roles at the central neuronal system but, hyperactivity of NMDARs could contribute to neurodegenerative diseases. Therefore, understanding the activation mechanism of NMDARs is important as it may lead to the development of new treatments for neurodegenerative diseases. In this thesis, human GluN1/GluN2A type NMDAR is modeled based on GluN1/GluN2B type NMDA structures that were resolved in 2014. To observe the dynamics of NMDA, 1.3 microseconds molecular dynamics simulations are performed for ligand-free and ligand-bound structures in the physiological environment. RMSD, RMSF, and PCA have been used to analyze the trajectory to understand the di↵erences in ligand-free and ligand-bound structures collective motions. From these analyses, the di↵erences in between ligand-free and ligand-bound simulations can be summarized as the following: Ligand-binding domain closure is observed, and these rearrangements are reflected to the transmembrane linkers upon ligand binding. Correlation maps from PCA analysis display more correlated motions in ligand-bound simulations. As a summary, mainly ligands act like an adhesive for the binding-domain by bringing the bi-lobe structures together and consequently, this is reflected in the overall dynamics of the protein. In the second part of this thesis, Xanthine Oxidase (XO) enzyme has been studied for the potency of bis-chalcones compounds. 8 bis-chalcones compounds that were provided to us from Serdar Burmalıo˘glu’s research group, showed high inhibition behavior on XO. These 8 molecules are docked to XO catalytic unit and 1000 run is performed for each compound. All compounds show better results than its approved drug which is allopurinol, however, the best ones are fifth and seventh compounds. In addition, all these compounds have three similar binding modes but, the first pose has the lowest free binding energy