Protein structure modeling and validation
Three-dimensional structure of both NS3 proteins (Fig. 1A) were modeled using Phyre2 server which has taken chain A of 2VBC (crystal structure of the NS3 protease-helicase from DENV) as template for modeling having 100% confidence and 67% identity. From the ProCheck analysis obtained from Ramachandran plot (Fig. 1B), it was observed that 88.8% residues were located in most favorable region, 9.8% were in additional allowed region, 0.4% residues in generously allowed regions whereas 0.9% of the residues located in disallowed region. The compatible Z score value of –10.71 (Fig. 1C) obtained from ProSA-web evaluation revealed that the modelled structure is fit within the range of native conformation of crystal structures [29]. Further, the overall residue energies of NS3 was largely negative (Fig. 1D). The modelled NS3 protein of ZIKV showed Levitt-Gerstein (LG) score of 5.060 by Protein Quality Predictor (ProQ) tool, it implies the high accuracy level of the predicted structure and taken to account as extremely good model. The ProQ LG score of more than 2.5 is needed to proposing a predicted structure is of very good quality [30]. By using ERRAT plot same assumptions were achieved, where the overall quality factor is 67.002%. All of the above out comes recommended the reliability of the proposed model.