Functional analysis of the conserved histidine residue of Bamboo mosaic virus capping enzyme in the activity for the formation of the covalent enzyme–m7GMP intermediate

AbstractThe alphavirus-like mRNA capping enzyme of Bamboo mosaic virus (BaMV) exhibits an AdoMet-dependent guanylyltransferase activity by which the methyl group of AdoMet is transferred to GTP, leading to the formation of m7GTP, and the m7GMP moiety is next transferred to the 5′ end of ppRNA via a covalent enzyme–m7GMP intermediate. The function of the conserved H68 of the BaMV capping enzyme in the intermediate formation was analyzed by mutagenesis in this study. The nature of the bond linking the enzyme and m7GMP was changed in the H68C mutant protein, strongly suggesting that H68 covalently binds to m7GMP in the intermediate