Flavivirus non-structural protein 5 N-terminal methyltransferase (NS5-MTase) (NS5-MTase)

The Flavivirus non-structural protein 5 (NS5) N-terminal methyltransferase is a multifunctional enzyme essential for the viral life cycle, specifically responsible for the formation of the 5' RNA cap structure (UniProtKB - P03314). This domain exhibits N7-guanine methyltransferase and 2'-O-ribose methyltransferase activities, which sequentially modify the viral RNA to resemble host mRNA (Dong et al., 2014, Antiviral Res). These modifications are critical for ensuring efficient translation of the viral genome by the host machinery and for protecting the viral RNA from degradation by 5'-3' exonucleases (Bollati et al., 2010, FEBS Lett). Additionally, the 2'-O-methylation serves as a key mechanism for immune evasion, as it prevents the activation of host innate immune sensors like RIG-I and MDA5 that typically recognize unmethylated viral RNA (Züst et al., 2011, Nature). Given its high conservation across the Flaviviridae family—including Dengue, Zika, and West Nile viruses—and its distinct structural features compared to human methyltransferases, it is a high-priority target for broad-spectrum antiviral drug development (Lim et al., 2015, Antiviral Res). Current drug discovery efforts focus on S-adenosyl-L-methionine (SAM) competitive inhibitors and allosteric inhibitors that disrupt the enzyme's interaction with RNA or its internal conformational stability (Brecher et al., 2015, Chem Biol Drug Des). Small molecules like Sinefungin have demonstrated proof-of-concept inhibition, though selectivity remains a challenge (PubMed: 24931016). Successful targeting of this enzyme could lead to treatments that both reduce viral replication and restore the host's ability to detect the infection (PubMed: 25809195).

Other names

NS5 methyltransferaseNS5-MTaseFlavivirus NS5 capping enzymeNS5 N-terminal domainRNA (guanine-N7-)-methyltransferaseNucleoside 2'-O-methyltransferase

Competitive inhibition of the S-adenosyl-L-methionine (SAM) binding site or the RNA-binding groove to prevent N7 and 2'-O methylation of viral RNA (PubMed: 24931016).