A computational H5N1 neuraminidase model and its binding to commercial drugs

Abstract

In order to understand the mechanisms of ligand binding and interaction between two commercial drugs (ligands), zanamivir and oseltamivir and H5N1 Influenza Virus Neuraminidase subtype N1, a three-dimensional model of N1-ligand (GenBank accession no. AAS654617) was initially generated by homology modeling using the 13 high-resolution X-ray structures of neuraminidase N2 and N9 as the template. With the aid of the molecular mechanics and molecular dynamics methods, the final implicit solvent refined model was obtained. It was, then, assessed by PROCHECK, PROSA and VERIFY3D. With this model, a flexible docking study was performed. The results show strong hydrogen bond interactions between the glycerol side chains of zanamivir and Arg29 of the N1. Common hydrogen bonds between the carboxyl groups and Arg279 were found for both drugs. It was also found that the Glu30, Asp62, Arg63, Arg204, Trp310, Tyr313, Glu336, Ile338, Trp348, Ala349 were observed to facilitate the enzyme-ligand non-bonding interactions as they are located within the radius of 5 Å from all atoms of both drugs. Charge distribution was evaluated using the semi-empirical AM1 method. The results show that the total net charges of the –NH side chain of zanamivir is less negative than that of oseltamivir. This is in contrast to what is observed for the amide and alkyl (ether/glycerol) side chains. In comparison of the binding free energies between the X-ray N2-ligand and N9-ligand complexes, N1-ligand binding is found to be less potent than N2 and N9 subtypes, while N2-ligand and N9-ligand are roughly comparable. In addition, it is interesting to observe that the binding free energies for all three subtypes of the zanamivir complexes are lower than those of oseltamivir.