Fig. 5.

Model of how coronavirus enzymes associate in the replicative complex. A model of the current state of knowledge on coronavirus enzymes and their co-factors is depicted. At the head of the complex nsp13 is in charge of the first capping step and disrupts RNA secondary structures during replication. Nsp12 may be in charge of the GMP transfer to RNA, while the third step of capping is performed by nsp14, bound to nsp12, and also in charge of RNA proofreading during nsp7/nsp8/nsp12-mediated RNA synthesis. Nsp16, in complex with nsp10, performs 2′-O-methylation. Since nsp16 has not been shown to tightly interact with other ORF1b-encoded nsps, nsp10/nsp16 complex may act right after replication has started.