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New insight into the architecture of oxy-anion pocket in unliganded conformation of GAT domains: A MD-simulation study

Bairagya, Hridoy R and Bansal, Manju (2016) New insight into the architecture of oxy-anion pocket in unliganded conformation of GAT domains: A MD-simulation study. In: PROTEINS-STRUCTURE FUNCTION AND BIOINFORMATICS, 84 (3). pp. 360-373.

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Official URL: http://dx.doi.org/10.1002/prot.24983

Abstract

Human Guanine Monophosphate Synthetase (hGMPS) converts XMP to GMP, and acts as a bifunctional enzyme with N-terminal ``glutaminase'' (GAT) and C-terminal ``synthetase'' domain. The enzyme is identified as a potential target for anticancer and immunosuppressive therapies. GAT domain of enzyme plays central role in metabolism, and contains conserved catalytic residues Cys104, His190, and Glu192. MD simulation studies on GAT domain suggest that position of oxyanion in unliganded conformation is occupied by one conserved water molecule (W1), which also stabilizes that pocket. This position is occupied by a negatively charged atom of the substrate or ligand in ligand bound crystal structures. In fact, MD simulation study of Ser75 to Val indicates that W1 conserved water molecule is stabilized by Ser75, while Thr152, and His190 also act as anchor residues to maintain appropriate architecture of oxyanion pocket through water mediated H-bond interactions. Possibly, four conserved water molecules stabilize oxyanion hole in unliganded state, but they vacate these positions when the enzyme (hGMPS)-substrate complex is formed. Thus this study not only reveals functionally important role of conserved water molecules in GAT domain, but also highlights essential role of other non-catalytic residues such as Ser75 and Thr152 in this enzymatic domain. The results from this computational study could be of interest to experimental community and provide a testable hypothesis for experimental validation. Conserved sites of water molecules near and at oxyanion hole highlight structural importance of water molecules and suggest a rethink of the conventional definition of chemical geometry of inhibitor binding site.

Item Type: Journal Article
Additional Information: Copy right for this article belongs to the WILEY-BLACKWELL, 111 RIVER ST, HOBOKEN 07030-5774, NJ USA
Keywords: oxyanion hole; conserved water molecules; MD-simulation; hGMPS enzyme
Department/Centre: Division of Biological Sciences > Molecular Biophysics Unit
Depositing User: Id for Latest eprints
Date Deposited: 29 Apr 2016 05:55
Last Modified: 29 Apr 2016 05:55
URI: http://eprints.iisc.ac.in/id/eprint/53735

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