Characterization of the NiRAN domain from RNA-dependent RNA polymerase provides insights into a potential therapeutic target against SARS-CoV-2
Fig 5
SARS-CoV-2 RdRp exhibits a kinase/phosphotransferase like activity.
(A) The CoV-2 RdRp exhibits a kinase like activity akin to that of purified human Akt2. While mutations in the probable NiRAN active site (K73A, D218A) cause decline in the kinase like catalytic activity of the SARS-CoV-2 RdRp, mutating the RdRp replication active site (D760A+D761A) has negligible effect on the same. The ATP binding protein Bovine Serum albumin serves as a negative control (Data points show mean and standard error. The connecting curves represent non-linear regressions). (B) MS-MS spectra profile for peptide KSLVSKGTLVQTK from Histone H1 treated with SARS-CoV-2 RdRp in presence of ATP and Mg2+ shows the phosphorylation at two serine residues. (C) MS-MS spectra profile for the same peptide from Histone H1 treated with human Akt2 in presence of ATP and Mg2+ shows the phosphorylation at a single threonine residue. (D) MS-MS spectra profile for the aforementioned peptide from Histone H1 treated with SARS-CoV-2 RdRp in the presence of only Mg2+ shows no phosphorylation, confirming the phosphotransferase activity of SARS-CoV-2 RdRp NiRAN domain (Further details are presented in S7 and S8 Figs and S8 Table).