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 Non-canonical RNA dependent RNA polymerase (RdRp) activity of ORF8 protein in SARS-CoV-2: Equivocal biological significance
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  • Venkatesan Ramya,
  • Karuppiah Prakash Shyam ,
  • Rajkumar Prabhakaran,
  • Vignesh Kalimuthu,
  • Sathya Priya Krishnamoorthy,
  • Balamuthu Kadalmani
Venkatesan Ramya
Bharathidasan University

Corresponding Author:[email protected]

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Karuppiah Prakash Shyam
VVD and Sons Private Limited
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Rajkumar Prabhakaran
VVD and Sons Private Limited
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Vignesh Kalimuthu
Bharathidasan University
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Sathya Priya Krishnamoorthy
Bharathidasan University
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Balamuthu Kadalmani
Bharathidasan University
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Abstract

No current treatment options were successful in containing the ongoing pandemic COVID-19 caused by SARS-CoV-2. It is essential to understand the molecular players of SARS-CoV-2 to find a suitable treatment method and to develop an effective antiviral drug as early as possible. Global researchers have undertaken accelerated structural studies of key proteins involved in host-virus interaction, replication, and transcription. In silico studies support structural biologist with preliminary information to efficiently drive further studies and characterization. From the genome sequence, most SARS-CoV-2 annotated ORF has a conserved sequence similar to SARS-CoV-1, except for ORF8 and ORF10. The function of ORF8 protein in SARS-CoV-2 is uncertain. Herein, we had modelled the ORF8 protein and studied its putative function using various substrates as a probe to determine its biological significance. The modelled SARS-CoV-2 (mORF87A) protein shows IgG characteristic folds and thus may belong to IgG superfamily. Further, we studied the binding efficacy of various antiviral drugs against the modelled ORF8 of SARS-CoV-2 (mORF8) to repurpose the drug and to use them as a probe to study its function by studying the binding/active sites interaction. Remdesivir had the highest binding affinity to ORF8 protein of SARS-CoV-2. The high affinity of the adenosine analogue yields critical information about the non-canonical RNA dependent RNA polymerase (RdRp) function of ORF8 protein. We hypothesize that the ORF8 protein may be a non-canonical RdRp in SARS-CoV-2 with ability to bind to canonical nsp12 complex.