InterPro: IPR019602 mRNA capping enzyme, large subunit, ATPase/guanylyltransferase, virus

Viral mRNA capping enzymes catalyse the first two reactions in the mRNA cap formation pathway. They are a heterodimer consisting of a large and small subunit.

This domain is the N terminus of the large subunit viral mRNA capping enzyme, and carries both the ATPase and the guanylyltransferase activities of the enzyme. The guanylyltransferase enzymatic region runs from residues 242 (leucine)-273(arginine) [1], the core of the active site being the lysine residue at 260 [2]. The ATPase activity is at the very N-terminal part of the domain [3].