ContentsFunctionmRNA capping enzyme (Mce) is a multifunctional protein with RNA triphosphatase, RNA guanylyltransferase, RNA methyltransferase and transcription factor activities. The 5' cap of mRNA is required for its stability and efficient translation. Mce activity entails the transfer of GMP from GTP to the 5'-diphosphate end of mRNA via a enzyme-(lysyl-GMP) intermediate by RNA triphosphatase and RNA guanylyltransferaseand finally the GpppRNA is converted to m7GpppRNA by RNA methyltransferase. In Vaccinia virus the active site is at Lys260 within the conserved motif KxDG in the catalytic subunit[1]. RelevanceInhibition of Mce may provide a route for selecting therapeutic targeting of cancer cells which acquired deregulated c-Myc which is a potent driver of many human cancers[2] Structural highlightsVaccinia virus mRNA capping enzyme catalytic subunit and regulatory subunit complex with SAH and GTP (PDB code 4ckb). The 3D structure of Vaccinia virus Mce shows the regulatory subunit or RNA triphosphatase domain which forms a hydrophilic tunnel. The tunnel is lined with charged residues with one half of the internal surface is lined almost exclusively with basic residues (colored in royalblue) and the other half with acidic residues (colored in red). The structure shows the catalytic subunit or guanylyltransferase which contains the active site that binds the GTP via two motifs rich in basic residues[3].
3D structures of mRNA capping enzymemRNA capping enzyme 3D structures References
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This page was last modified 10:08, 5 January 2026.