Exploring the Conformational Dynamics of RNA Dependent RNA Polymerase of SARS-CoV-2 in the Presence of Various Nucleotide Analogues

RNA dependent RNA polymerase (RdRP) from positive stranded RNA viruses has always been a hot target for designing of new drugs as it is responsible for viral replication. The major class of drugs that are targeted against RdRP are nucleotide analogues. An extensive docking and molecular dynamics study describing the role of natural nucleotides (NTPs) and its analogues in imparting an inhibitory effect on the RdRP has been presented here. RdRP simulations in its apo, NTP-bound and analogue-bound form have been performed for a cumulative time of 1.9 μs. The conformational flexibility of the RdRP molecule was explored using Principal Component Analysis (PCA) and Markov State Modeling (MSM) Analysis. PCA inferred the presence of correlated motions along the conserved motifs of the RdRP. The ligand binding motif F and template binding motif G showed motions that are negatively correlated with one another. LYS 551, ARG 553 and ARG 555 which are a part of the motif F appear to form strong interactions with the ligand molecules. ARG 836, a primer binding residue was observed to strongly bind to the nucleotide analogues. The MSM analysis helped to observe different conformational states explored by the RdRP. The ensemble docking of the ligands on the Markov states suggested the involvement of the above residues in ligand interactions. The Markov states obtained clearly demarcated the open and closed conformations. The closed states were observed to have more favorable docking of the ligands. MSM analysis predicted a probable inhibitory mechanism involving the closing of the template entry site by reduction in the distance between the flanking finger and thumb subdomain.