Structural basis of RNA cap modification by SARS-CoV-2

RNA capping of SARS-CoV-2 is catalyzed by several nonstructural proteins such as nsp13 (triphosphatase and  helicase), nsp14 (3'→5' mismatch exonuclease and cap guanine-N7 methyltransferase) and nsp16 (cap ribose 2'-O methyltransferase and elusive guanylyl transferase). Nsp16 forms a complex with nsp10 to convert Cap-0 to Cap-1 by methylating the ribose 2'-O of the first nucleotide of the transcribed mRNA using S-adenosyl methionine as the methyl donor. The high-resolution structure of SARS-CoV-2 nsp16/nsp10 in complex with the S-adenosyl methionine and its target RNA cap was reported.