Non-structural protein 5 methyltransferase domain (NS5-MTase)

The Non-structural protein 5 (NS5) methyltransferase domain is a highly conserved N-terminal domain of the multifunctional NS5 protein found in orthoflaviviruses such as Dengue, Zika, and West Nile viruses. It serves as a critical enzyme in the viral replication cycle by catalyzing the sequential N-7 and 2'-O-methylation of the 5'-terminal RNA cap structure, which is essential for viral mRNA translation and stability. Beyond its role in capping, the domain assists the virus in evading the host's innate immune system by mimicking cellular mRNA, thereby preventing detection by host pattern recognition receptors. The methyltransferase domain also functionally interacts with the C-terminal RNA-dependent RNA polymerase (RdRp) domain to enhance the efficiency of viral RNA synthesis. Due to its essential nature and high conservation across pathogenic flaviviruses, it is considered a primary target for the development of broad-spectrum antiviral drugs. Current therapeutic strategies focus on small molecules that competitively inhibit the binding of the methyl donor S-adenosyl-L-methionine (SAM) or the RNA substrate itself.

Other names

NS5-MTaseNS5 MTaseFlavivirus methyltransferaseN-terminal domain of NS5Non-structural protein 5 N-terminal methyltransferaseSAM-dependent methyltransferase domain

Competitive inhibition of the S-adenosyl-L-methionine (SAM) binding site or the RNA cap-binding site, which prevents viral mRNA methylation and leads to inhibition of viral translation and replication [1, 8, 11, 14].