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.

Meenakshi Sundari Rajendran1*, Raj Kumar Prabhakaran2**, Poornima Kannappan1** Department of Biochemistry, Karpagam Academy of Higher Education, Coimbatore, Tamil Nadu, India.** Manonmaniam Sundaranar University, Tirunelveli, Tamilnadu, India.Email: [email protected];[email protected] address: Department of Biochemistry, Karpagam Academy of Higher Education, Coimbatore, Tamil Nadu, India.