FAD capping

Viral RNA-dependent RNA polymerase initiates transcription/replication at a flavin adenine dinucleotide (FAD), resulting in a 5'- FAD cap on viral RNAs. In this way, recognition of viral 5' RNA by host antiviral receptors can be bypassed.

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Enzymatic reaction:
FAD nucleotidyltransferase (RNA-dependent)
RNA nucleotidyltransferase (RNA-dependent) EC 2.7.7.48 RHEA:21248


Mechanism Viral RdRp are characterized by a conserved motif in which two conserved aspartic acid residues are bound to two magnesium ions. The reaction begins with the deprotonation of primer's 3' OH, in a manner that doesn't require a base . Subsequently, the 3'-oxygen acts as a nucleophile to attack the phosphate bond and eventually releases a pyrophosphate.

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