Function
mRNA 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].
Relevance
Inhibition 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 highlights
(PDB code 4ckb). The 3D structure of Vaccinia virus Mce shows the regulatory subunit or RNA triphosphatase domain which forms a hydrophilic tunnel. The . The structure shows the catalytic subunit or guanylyltransferase which contains the active site that binds the GTP via rich in basic residues[3].
- . Water molecule is shown as red sphere.
- (colored in royalblue), which are situated in GTP-binding site.
- .
- .
