Expression and purification of tag-free SARS-CoV-2 RNA-dependent RNA polymerase in Escherichia coli

The RNA-dependent-RNA polymerase (RdRp) from SARS-CoV-2 is an important drug target as it is responsible for viral RNA genome replication. Efficient production of recombinant RdRp is important in screening antivirals to treat COVID-19. Here we present our protocol for expression of tag-free replication complex proteins in E. coli and subsequent purification. Despite the added complexity of multiple purification steps, our methods provide greater activity and yield at lower cost and are faster than baculovirus expression systems.