Role of ATP in the RNA Translocation Mechanism of SARS-CoV-2 NSP13 Helicase

J Phys Chem B. 2021 Aug 12;125(31):8787-8796. doi: 10.1021/acs.jpcb.1c04528. Epub 2021 Jul 30.

Abstract

The COVID-19 pandemic has demonstrated the need to develop potent and transferable therapeutics to treat coronavirus infections. Numerous antiviral targets are being investigated, but nonstructural protein 13 (nsp13) stands out as a highly conserved and yet understudied target. Nsp13 is a superfamily 1 (SF1) helicase that translocates along and unwinds viral RNA in an ATP-dependent manner. Currently, there are no available structures of nsp13 from SARS-CoV-1 or SARS-CoV-2 with either ATP or RNA bound, which presents a significant hurdle to the rational design of therapeutics. To address this knowledge gap, we have built models of SARS-CoV-2 nsp13 in Apo, ATP, ssRNA and ssRNA+ATP substrate states. Using 30 μs of a Gaussian-accelerated molecular dynamics simulation (at least 6 μs per substrate state), these models were confirmed to maintain substrate binding poses that are similar to other SF1 helicases. A Gaussian mixture model and linear discriminant analysis structural clustering protocol was used to identify key structural states of the ATP-dependent RNA translocation mechanism. Namely, four RNA-nsp13 structures are identified that exhibit ATP-dependent populations and support the inchworm mechanism for translocation. These four states are characterized by different RNA-binding poses for motifs Ia, IV, and V and suggest a power stroke-like motion of domain 2A relative to domain 1A. This structural and mechanistic insight of nsp13 RNA translocation presents novel targets for the further development of antivirals.

MeSH terms

  • Adenosine Triphosphate
  • Antiviral Agents
  • COVID-19*
  • Humans
  • Pandemics
  • RNA Helicases / genetics
  • RNA, Viral / genetics
  • SARS-CoV-2*
  • Viral Nonstructural Proteins / genetics

Substances

  • Antiviral Agents
  • RNA, Viral
  • Viral Nonstructural Proteins
  • Adenosine Triphosphate
  • RNA Helicases