Inhibitory Effect of Bridged Nucleosides on Thermus aquaticus DNA Polymerase and Insight into the Binding Interactions

PLoS One. 2016 Jan 28;11(1):e0147234. doi: 10.1371/journal.pone.0147234. eCollection 2016.

Abstract

Modified nucleosides have the potential to inhibit DNA polymerases for the treatment of viral infections and cancer. With the hope of developing potent drug candidates by the modification of the 2',4'-position of the ribose with the inclusion of a bridge, efforts were focused on the inhibition of Taq DNA polymerase using quantitative real time PCR, and the results revealed the significant inhibitory effects of 2',4'-bridged thymidine nucleoside on the polymerase. Study on the mode of inhibition revealed the competitive mechanism with which the 2',4'-bridged thymidine operates. With a Ki value of 9.7 ± 1.1 μM, the 2',4'-bridged thymidine proved to be a very promising inhibitor. Additionally, docking analysis showed that all the nucleosides including 2',4'-bridged thymidine were able to dock in the active site, indicating that the substrate analogs reflect a structural complementarity to the enzyme active site. The analysis also provided evidence that Asp610 was a key binding site for 2',4'-bridged thymidine. Molecular dynamics (MD) simulations were performed to further understand the conformational variations of the binding. The root-mean-square deviation (RMSD) values for the peptide backbone of the enzyme and the nitrogenous base of the inhibitor stabilized within 0.8 and 0.2 ns, respectively. Furthermore, the MD analysis indicates substantial conformational change in the ligand (inhibitor) as the nitrogenous base rotated anticlockwise with respect to the sugar moiety, complemented by the formation of several new hydrogen bonds where Arg587 served as a pivot axis for binding formation. In conclusion, the active site inhibition of Taq DNA polymerase by 2',4'-bridged thymidine suggests the potential of bridged nucleosides as drug candidates.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / antagonists & inhibitors
  • Bacterial Proteins / chemistry*
  • Catalytic Domain
  • DNA Replication / drug effects
  • Enzyme Inhibitors / chemistry*
  • Hydrogen Bonding
  • Molecular Docking Simulation
  • Molecular Dynamics Simulation
  • Protein Binding
  • Taq Polymerase / antagonists & inhibitors
  • Taq Polymerase / chemistry*
  • Thermus / enzymology
  • Thymidine / analogs & derivatives*
  • Thymidine / chemistry*

Substances

  • Bacterial Proteins
  • Enzyme Inhibitors
  • Taq Polymerase
  • Thymidine

Grants and funding

This work was supported by a grant from Bio-Synthesis Inc. (14-9089) to SK. AC, ESK, XL and MC are employed by Bio-Synthesis Inc. Bio-Synthesis Inc. provided support in the form of salaries for authors AC, ESK, XL and MC, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the ‘author contributions’ section.